1. |
- Achberger, C, et al.
(author)
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Performance of the Rossby Centre regional atmospheric model in Southern Sweden: comparison of simulated and observed precipitation
- 2003
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In: Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 1434-4483 .- 0177-798X. ; 76:3-4, s. 219-234
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Journal article (peer-reviewed)abstract
- Two climate model simulations made with the Rossby Centre regional Atmospheric model version I (RCA1) are evaluated for the precipitation climate in Scania, southern-most Sweden. These simulations are driven by the HadCM2 and the ECHAM4/OPYC3 global circulation models (GCMs) for 10 years. Output from the global and the regional simulations are compared with an observational data set, constructed from a dense precipitation gauge network in Scania. Area-averaged time series corresponding to the size and location of the RCA1 grid points in Scania have been created (the Scanian Data Set). This data set was compared to a commonly used gridded surface climatology provided by the Climatic Research Unit (CRU). Relatively large differences were found, mainly due to the fact that the CRU-climatology uses fewer stations and lacks a correction for rain-gauge under-catch. This underlines the importance of the data set chosen for model evaluations. The validation is carried out at a large scale including the whole area of Scania and at the finest resolution of RCA1 (the grid point level). When integrated over the whole area of Scania, RCA1 improves the shape of the annual precipitation cycle and the inter-annual variability compared to output from the GCMs. The RCA1 control climate is generally too wet compared to the observations. At the grid point level, RCA1 improves the simulation of the variability compared to the GCMs. There is a strong positive correlation between precipitation and altitude in all seasons in the observations. This relationship is, however, much weaker and even reversed in the RCA1 simulations. Analysis of the dense rain gauge network reveals features of spatial variability at around 20-35 km in the area and indicates that a finer resolution is needed if the spatial variability in the area is to be better captured by RCA1.
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2. |
- An, Dong, et al.
(author)
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Evidence of climate shift for temperature and precipitation extremes across Gansu Province in China
- 2020
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In: Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 1434-4483 .- 0177-798X. ; 139:3-4, s. 1137-1149
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Journal article (peer-reviewed)abstract
- Temperature and precipitation extremes are the dominant causes of natural disasters. In this study, seven indices of extreme temperature and precipitation events in Gansu Province, China, were analysed for the period 1961–2017. An abrupt climate shift was recorded during 1980–1981. Thus, the study period was divided into a preshift (before the climate shift) period 1961–1980 and an aftshift (after the climate shift) period 1981–2017. Comparison of mean extreme indices for preshift and aftshift periods was performed for the purpose of exploring possible increasing/decreasing patterns. Generalized extreme value (GEV) distribution was applied spatially to fit the extreme indices with return periods up to 100 years for preshift/aftshift periods. Singular value decomposition (SVD) was adopted to investigate possible correlation between the extreme climate events and indices of large-scale atmospheric circulation. The results indicate that changes in mean and return levels between the preshift and aftshift periods vary significantly in time and space for different extreme indices. Increase in extreme temperature regarding magnitude and frequency for the aftshift period as compared with the preshift period suggests a change to a warmer and more extreme climate during recent years. Changes in precipitation extremes were different in southern and northern parts of Gansu. The precipitation extremes in the north have increased that can result in more serious floods and droughts in the future. SVD analyses revealed a complex pattern of correlation between climate extremes and indices of large-scale atmospheric circulation. Strengthening of westerlies and weakening of the south summer monsoon contribute to the complex changing patterns of precipitation extremes. Results in this study will contribute to disaster risk prevention and better water management in this area.
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5. |
- Bey, Ergün, et al.
(author)
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Long-term air temperature trends in North Cyprus
- 2024
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In: Journal of Theoretical and Applied Climatology. - : Springer. - 0177-798X .- 1434-4483. ; 155, s. 1113-1122
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Journal article (peer-reviewed)abstract
- The Eastern Mediterranean region is a major climate change hotspot. The island of Cyprus is likely to face increases in the frequency and intensity of hotter weather conditions and heatwaves in the near future. Studies conducted on the long-term temperature changes in Cyprus are very limited. Here, we present an updated and most detailed assessment of the maximum, minimum, mean and diurnal temperature series in North Cyprus for the period 1975–2021. Data obtained from the meterological stations of North Cyprus have been analysed using Mann–Kendal (MK) test and Theil–Sen slope estimator. Overall the mean minimum temperature trend (Tmin) showed the highest warming rate 0.61 (0.24 ≤ Tmin ≤ 0.99)°C decade−1 followed by the mean temperature trend (Tmean) 0.38 (0.29 ≤ Tmean ≤ 0.50) °C decade−1 and the mean maximum temperature trend (Tmax) 0.28 (0 ≤ Tmax ≤ 0.50) °C decade−1. The magnitude of the warming trend observed in the overall mean minimum temperature of North Cyprus 0.61 °C decade−1, is one of the fastest warming trends reported in the literature. A negative association was detected between the direction of prevailing winds of North Cyprus and the magnitude of increase in the mean temperature trends of the locations with coastal Mediterranean climate, which has pointed out the importance of prevailing winds regarding their cooling effect in coastal areas. The diurnal temperature range trend of North Cyprus indicates an apparent decrease (− 0.33 °C decade−1). The warming impact of urban heat island effect was detected in temperature trends of Nicosia in the Mesaoria plain. The information provided here is invaluable to consider in any climate assessment and adaptation plan in Cyprus. If the current warming trend persists into the future, it will devastatingly impact all sectors and natural systems in the region.
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6. |
- Björklund, Jesper, 1979, et al.
(author)
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Advances towards improved low-frequency tree-ring reconstructions, using an updated Pinus sylvestris L. MXD network from the Scandinavian Mountains
- 2013
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In: Journal of Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 113:3-4, s. 697-710
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Journal article (peer-reviewed)abstract
- The dendrochronological use of the parameter maximum density (MXD) in Pinus Sylvestris L., at high latitudes, has provided valuable insights into past summer temperature variations. Few long MXD chronologies, from climatically coherent regions, exist today, with the exception being in northern Europe. Five, 500-year-long, Fennoscandian, MXD chronologies were compared with regard to their common variability and climate sensitivity. They were used to test Signal-free standardization techniques, to improve inferences of low-frequency temperature variations. Climate analysis showed that, in accordance with previous studies on MXD in Fennoscandia, the summer temperature signal is robust (R (2) > 50 %) and reliable over this climatically coherent region. A combination of Individual standardization and regional curve standardization is recommended to refine long-term variability from these MXD chronologies and relieve problems arising from low replication and standardization end-effects.
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7. |
- Burauskaite-Harju, Agne, et al.
(author)
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Characterizing and visualizing spatio-temporal patterns in hourly precipitation records
- 2012
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In: Journal of Theoretical and Applied Climatology. - : Springer. - 0177-798X .- 1434-4483. ; 109:3-4, s. 333-343
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Journal article (peer-reviewed)abstract
- We develop new techniques to summarize and visualize spatial patterns of coincidence in weather events such as more or less heavy precipitation at a network of meteorological stations. The cosine similarity measure, which has a simple probabilistic interpretation for vectors of binary data, is generalized to characterize spatial dependencies of events that may reach different stations with a variable time lag. More specifically, we reduce such patterns into three parameters (dominant time lag, maximum cross-similarity, and window-maximum similarity) that can easily be computed for each pair of stations in a network. Furthermore, we visualize such threeparameter summaries by using colour-coded maps of dependencies to a given reference station and distance-decay plots for the entire network. Applications to hourly precipitation data from a network of 93 stations in Sweden illustrate how this method can be used to explore spatial patterns in the temporal synchrony of precipitation events.
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8. |
- Burauskaite-Harju, Agne, et al.
(author)
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Diagnostics for tail dependence in time-lagged random fields of precipitation
- 2013
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In: Journal of Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 112:3-4, s. 629-636
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Journal article (peer-reviewed)abstract
- Weather extremes often occur along fronts passing different sites with some time lag. Here, we show how such temporal patterns can be taken into account when exploring inter-site dependence of extremes. We incorporate time lags into existing models and into measures of extremal associations and their relation to the distance between the investigated sites. Furthermore, we define summarizing parameters that can be used to explore tail dependence for a whole network of stations in the presence of fixed or stochastic time lags. Analysis of hourly precipitation data from Sweden showed that our methods can prevent underestimation of the strength and spatial extent of tail dependencies.
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9. |
- Chu, T, et al.
(author)
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Statistical downscaling of daily mean temperature, pan evaporation and precipitation for climate change scenarios in Haihe River, China
- 2010
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In: Journal of Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 99:1-2, s. 149-161
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Journal article (peer-reviewed)abstract
- A statistical downscaling method (SDSM) was evaluated by simultaneously downscaling air temperature, evaporation, and precipitation in Haihe River basin, China. The data used for evaluation were large-scale atmospheric data encompassing daily NCEP/NCAR reanalysis data and the daily mean climate model results for scenarios A2 and B2 of the HadCM3 model. Selected as climate variables for downscaling were measured daily mean air temperature, pan evaporation, and precipitation data (1961-2000) from 11 weather stations in the Haihe River basin. The results obtained from SDSM showed that: (1) the pattern of change in and numerical values of the climate variables can be reasonably simulated, with the coefficients of determination between observed and downscaled mean temperature, pan evaporation, and precipitation being 99%, 93%, and 73%, respectively; (2) systematic errors existed in simulating extreme events, but the results were acceptable for practical applications; and (3) the mean air temperature would increase by about 0.7A degrees C during 2011 similar to 2040; the total annual precipitation would decrease by about 7% in A2 scenario but increase by about 4% in B2 scenario; and there were no apparent changes in pan evaporation. It was concluded that in the next 30 years, climate would be warmer and drier, extreme events could be more intense, and autumn might be the most distinct season among all the changes.
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10. |
- Coelho, C.A.S., et al.
(author)
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Exploring the impacts of the tropical Pacific SST on the precipitation patterns over South America during ENSO periods
- 2002
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In: Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 1434-4483 .- 0177-798X. ; 71:3-4, s. 185-197
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Journal article (peer-reviewed)abstract
- Summary Previous studies on precipitation over South America that strongly support the existence of links between precipitation and SST anomalies in the Pacific Ocean have identified specific regions where the ENSO signal is particularly stronger. Northeast of Brazil and some parts of southern South America are examples of these regions. However, the same attention was not taken to identify which regions in the Central and East Pacific ocean are better correlated with the South America precipitation during extreme ENSO events, and also which are the transition regions of the precipitation signal over South America during these events. Coincident periods of ENSO events for both SST over the tropical Pacific ocean and monthly precipitation sums from many observational stations over South America were selected and analyzed. Two statistical methods were used for the data analysis: Singular Value Decomposition (SVD) and Simple Linear Correlation (SLC). The SVD results for warmer events in the Pacific corroborate previous ones and also clearly identified a transition region between the drier conditions in the Northeast of Brazil and the wetter conditions in the Southeast/South of Brazil. Transition regions were also determined over Peru and central Amazon. The SLC results indicated that the SST anomalies in the tropical east Pacific ocean has the strongest influence in the South American precipitation during El Niño events. During La Niña events the central area of the Pacific, around 180°, has shown a more significant influence.
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11. |
- Diodato, Nazzareno, et al.
(author)
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Empirical modelling of snow cover duration patterns in complex terrains of Italy
- 2022
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In: Journal of Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 147, s. 1195-1212
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Journal article (peer-reviewed)abstract
- Snow cover duration is a crucial climate change indicator. However, measurements of days with snow cover on the ground (DSG) are limited, especially in complex terrains, and existing measurements are fragmentary and cover only relatively short time periods. Here, we provide observational and modelling evidence that it is possible to produce reliable time-series of DSG for Italy based on instrumental measurements, and historical documentary data derived from various sources, from a limited set of stations and areas in the central-southern Apennines (CSA) of Italy. The adopted modelling approach reveals that DSG estimates in most settings in Italy can be driven by climate factors occurring in the CSA. Taking into account spatial scale-dependence, a parsimonious model was developed by incorporating elevation, winter and spring temperatures, a large-scale circulation index (the Atlantic Multidecadal Variability, AMV) and a snow-severity index, with in situ DSG data, based on a core snow cover dataset covering 97 years (88% coverage in the 1907–2018 period and the rest, discontinuously from 1683 to 1895, from historical data of the Benevento station). The model was validated on the basis of the identification of contemporary snow cover patterns and historical evidence of summer snow cover in high massifs. Beyond the CSA, validation obtained across terrains of varying complexity in both the northern and southern sectors of the peninsula indicate that the model holds potential for applications in a broad range of geographical settings and climatic situations of Italy. This article advances the study of past, present and future DSG changes in the central Mediterranean region.
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12. |
- El-kenawy, El-Sayed M., et al.
(author)
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Sunshine duration measurements and predictions in Saharan Algeria region : an improved ensemble learning approach
- 2022
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In: Journal of Theoretical and Applied Climatology. - : Springer. - 0177-798X .- 1434-4483. ; 147:3-4, s. 1015-1031
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Journal article (peer-reviewed)abstract
- Sunshine duration is an important atmospheric indicator used in many agricultural, architectural, and solar energy applications (photovoltaics, thermal systems, and passive building design). Hence, it should be estimated accurately for areas with low-quality data or unavailable precise measurements. This paper aimed to obtain a sunshine duration measurement database in Algeria’s south region and also to study the applicability of computational models to predict them. This work develops ensemble learning models for assessing daily sunshine duration with meteorological datasets that include daily mean relative humidity, daily mean air temperature, daily maximum air temperature, daily minimum air temperature, and daily temperature range as input. The study proposes a unique hybrid model, combining grey wolf and stochastic fractal search (GWO-SFS) optimization algorithms with the random forest regressor ensemble. A pre-feature selection process improved the newly suggested model. Various commonly adopted algorithms in relevant studies have been considered as references for evaluating the new hybrid algorithm. The accuracy of models was examined as a function of some frequently used statistical pointers, as well as the Wilcoxon rank-sum test. Besides, the models were evaluated according to the several input combinations. The numerical experiments show that the proposed optimization ensemble with feature preprocessing outperforms stand-alone models in terms of prediction accuracy and robustness, where relative root mean square errors are reduced by over 20% for all considered locations. In addition, all correlation coefficients are higher than 0.999. Moreover, the proposed model, with RMSEs lower than 0.4884 hours, shows significantly superior performances compared to previously proposed models in the literature.
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13. |
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14. |
- Fazel, Nasim, et al.
(author)
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Regionalization of precipitation characteristics in Iran's Lake Urmia basin
- 2018
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In: Journal of Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 132:1-2, s. 363-373
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Journal article (peer-reviewed)abstract
- Lake Urmia in northwest Iran, once one of the largest hypersaline lakes in the world, has shrunk by almost 90% in area and 80% in volume during the last four decades. To improve the understanding of regional differences in water availability throughout the region and to refine the existing information on precipitation variability, this study investigated the spatial pattern of precipitation for the Lake Urmia basin. Daily rainfall time series from 122 precipitation stations with different record lengths were used to extract 15 statistical descriptors comprising 25th percentile, 75th percentile, and coefficient of variation for annual and seasonal total precipitation. Principal component analysis in association with cluster analysis identified three main homogeneous precipitation groups in the lake basin. The first sub-region (group 1) includes stations located in the center and southeast; the second sub-region (group 2) covers mostly northern and northeastern part of the basin, and the third sub-region (group 3) covers the western and southern edges of the basin. Results of principal component (PC) and clustering analyses showed that seasonal precipitation variation is the most important feature controlling the spatial pattern of precipitation in the lake basin. The 25th and 75th percentiles of winter and autumn are the most important variables controlling the spatial pattern of the first rotated principal component explaining about 32% of the total variance. Summer and spring precipitation variations are the most important variables in the second and third rotated principal components, respectively. Seasonal variation in precipitation amount and seasonality are explained by topography and influenced by the lake and westerly winds that are related to the strength of the North Atlantic Oscillation. Despite using incomplete time series with different lengths, the identified sub-regions are physically meaningful.
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15. |
- Fonseca, Ricardo, et al.
(author)
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High-Resolution Dynamical Downscaling of Re-Analysis Data over the Kerguelen Islands using the WRF Model
- 2019
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In: Journal of Theoretical and Applied Climatology. - : Springer. - 0177-798X .- 1434-4483. ; 135:3-4, s. 1259-1277
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Journal article (peer-reviewed)abstract
- We have used the Weather Research and Forecasting (WRF) model to simulate the climate of the Kerguelen Islands (49° S, 69° E) and investigate its inter-annual variability. Here, we have dynamically downscaled 30 years of the Climate Forecast System Reanalysis (CFSR) over these islands at 3-km horizontal resolution. The model output is found to agree well with the station and radiosonde data at the Port-aux-Français station, the only location in the islands for which observational data is available. An analysis of the seasonal mean WRF data showed a general increase in precipitation and decrease in temperature with elevation. The largest seasonal rainfall amounts occur at the highest elevations of the Cook Ice Cap in winter where the summer mean temperature is around 0 °C. Five modes of variability are considered: conventional and Modoki El Niño-Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), Subtropical IOD (SIOD) and Southern Annular Mode (SAM). It is concluded that a key mechanism by which these modes impact the local climate is through interaction with the diurnal cycle in particular in the summer season when it has a larger magnitude. One of the most affected regions is the area just to the east of the Cook Ice Cap extending into the lower elevations between the Gallieni and Courbet Peninsulas. The WRF simulation shows that despite the small annual variability, the atmospheric flow in the Kerguelen Islands is rather complex which may also be the case for the other islands located in the Southern Hemisphere at similar latitudes.
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16. |
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17. |
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18. |
- Gustafsson, David, et al.
(author)
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The surface energy balance of a snow cover : comparing measurements to two different simulation models
- 2001
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In: Journal of Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 70:1-4, s. 81-96
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Journal article (peer-reviewed)abstract
- We compared two one-dimensional simulation models for heat and water fluxes in the soil-snow-atmosphere system with respect to their mathematical formulations of the surface heat exchange and the snow pack evolution. They were chosen as examples of a simple one-layer snow model and a more detailed multiple-layer snow model (SNTHERM). The snow models were combined with the same one-dimensional model for the heat and water balance of the underlying soil (CoupModel). Data from an arable field in central Sweden (Marsta), covering two years (1997-1999) of soil temperature, snow depth and eddy-correlation measurements were successfully compared with the models. Conditions with a snow pack deeper or shallower than 10cm and bare soil resulted in similar discrepancies. The simulated net radiation and sensible heat flux were in good agreement with that measured during snow-covered periods, except for situations with snowmelt when the downward sensible heat flux was overestimated by 10-20 WM-2. The results showed that the uncertainties in parameter values were more important than the model formulation and that both models were useful in evaluating the limitations and uncertainties of the measurements.
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19. |
- Hu, Yumei, et al.
(author)
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The use of screening effects in modelling route-based daytime road surface temperature
- 2016
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In: Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 125:1, s. 303-319
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Journal article (peer-reviewed)abstract
- © 2015 The Author(s) Winter road maintenance is essential for road safety. Accurate predictions of the road surface temperature (RST) and conditions can enhance the efficiency of winter road maintenance. Screening effects, which encompass shading effects and the influence of the sky-view factor (ψs), influence RST distributions because they affect road surface radiation fluxes. In this work, light detection and ranging (Lidar) data are used to derive shadow patterns and ψs values, and the resulting shadow patterns are used to model route-based RST distributions along two stretches of road in Sweden. The shading patterns and road surface radiation fluxes calculated from the Lidar data generally agreed well with measured RST values. Variation in land use types and the angle between the road direction and solar azimuth may introduce uncertainties, and accounting for these factors may improve the results obtained in certain cases. A simple shading model that only accounts for the direct radiation at the instant of measurement is often sufficient to provide reasonably accurate RST estimates. However, in certain cases, such as those involving measurements close to sunset, it is important to consider the radiation accumulated over several hours. The inclusion of ψs improves the model performance even more in such cases. Overall, RST models based on the accumulated direct shortwave radiation offered an optimal balance of simplicity and accuracy. General radiation models were built for country road and highway environments, explaining up to 70 and 65 %, respectively, of the observed variation in RST along the corresponding stretches of road.
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20. |
- Iqbal, Waheed, et al.
(author)
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Mean climate and representation of jet streams in the CORDEX South Asia simulations by the regional climate model RCA4
- 2017
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In: Journal of Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 129:1-2, s. 1-19
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Journal article (peer-reviewed)abstract
- A number of simulations with the fourth release of the Rossby Center Regional Climate Model (RCA4) conducted within the COordinated Regional climate Downscaling EXperiment (CORDEX) framework for South Asia at 50 km horizontal resolution are evaluated for mean winter (December-March) and summer (June-September) climate during 1980-2005. The two driving data sets ERA-Interim reanalysis and the general circulation model EC-Earth have been analyzed besides the RCA4 simulations to address the added value. RCA4 successfully captures the mean climate in both the seasons. The biases in RCA4 appear to come from the driving data sets which are amplified after downscaling. The jet streams influencing the seasonal precipitation variability in both seasons are also analyzed. The spatial and quantitative analysis over CORDEX South Asia generally revealed the ability of RCA4 to capture the mean seasonal climate as well as the position and strength of the jet streams despite weak/strong jet representation in the driving data. The EC-Earth downscaled with RCA4 exhibited cold biases over the domain and a weak Somali jet over the Arabian Sea. Moreover, the moisture transport from the Arabian Sea during summer is pronounced in RCA4 simulations resulting in enhanced monsoon rainfall over northwestern parts of India. Both the Somali jet and the tropical easterly jet become stronger during strong summer monsoon years. However, there is robust impact of wet years in summer over the Somali jet. Wet-minus-dry composites in winter indicate strengthening (weakening) of the subtropical jet in RCA4 run by ERA-Interim (EC-Earth). The driving data have clear reflections on the RCA4 simulations.
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21. |
- Irannezhad, M., et al.
(author)
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Variability in Dryness and Wetness in Central Finland and the Role of Teleconnection Patterns
- 2015
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In: Journal of Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 122:3-4, s. 471-486
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Journal article (peer-reviewed)abstract
- Interannual variability in meteorological dryness and wetness in central Finland during the period 1959–2009 was analysed using Standardized Precipitation Index (SPI) on three timescales (annual, seasonal and monthly). For different time steps (12, 3 and 1 months) of SPI values (SPI12, SPI3 and SPI1), trends based on the Mann-Kendall non-parametric test and the most significant relationships with a number of climate teleconnection patterns based on Spearman correlation coefficient (rho) were determined. Analysis of the SPI values on different timescales showed a general decreasing trend in dryness and an increasing trend in wetness; only August showed an increasing trend in dryness. The longest wet period observed was 5 years (between 1988 and 1992), while the longest dry period was 4 years (in the mid-1960s). Wet conditions were more frequent than dry conditions and mainly occurred at extreme or moderate level. Typically, the extremely wet level was more frequent than the extremely dry level. The dry and wet conditions were negatively correlated with the East Atlantic/West Russia and Scandinavia teleconnection patterns and positively correlated with the North Atlantic Oscillation.
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22. |
- Jansson, Christer, et al.
(author)
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Near surface climate in an urban vegetated park and its surroundings
- 2007
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In: Journal of Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 89:34, s. 185-193
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Journal article (peer-reviewed)abstract
- Near surface climate was observed through temperature profiling from the surface to 2.47 m height in an urban vegetated park and its surroundings in central Stockholm, Sweden. Measurements were conducted during three summer days by mobile traverses. Air temperature differences between the built-up area and the park were in the range of 0.5-0.8°C during the day and reached a maximum of 2°C at sunset. The thermal stratification of the air was mainly stable in the park and unstable in the built-up area. Inverse air temperature profiles in the park were less stable in open than in shady areas, and close to neutral at midday. The most unstable air was found in the north-south orientated canyons in the early afternoon. Possible heat advection from the surroundings, and thus uncoupling between the surface and the air, was identified through temperature gradients pointing at different directions within the 2.47 m profile. Examples at midday indicated that warm air advected as far as 150 m into the park.
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23. |
- Johansson, Lars, et al.
(author)
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Towards the modelling of pedestrian wind speed using high-resolution digital surface models and statistical methods
- 2016
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In: Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 124:1, s. 189-203
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Journal article (peer-reviewed)abstract
- Wind is a complex phenomenon and a critical factor in assessing climatic conditions and pedestrian comfort within cities. To obtain spatial information on near-ground wind speed, 3D computational fluid dynamics (CFD) modelling is often used. This is a computationally intensive method which requires extensive computer resources and is time consuming. By using a simpler 2D method, larger areas can be processed and less time is required. This study attempts to model the relationship between near-ground wind speed and urban geometry using 2.5D raster data and variable selection methods. Such models can be implemented in a geographic information system (GIS) to assess the spatial distribution of wind speed at street level in complex urban environments at scales from neighbourhood to city. Wind speed data, 2 m above ground, is obtained from simulations by CFD modelling and used as a response variable. A number of derivatives calculated from high-resolution digital surface models (DSM) are used as potential predictors. A sequential variable selection algorithm followed by all-possible subset regression was used to select candidate models for further evaluation. The results show that the selected models explain general spatial wind speed pattern characteristics but the prediction errors are large, especially so in areas with high wind speeds. However, all selected models did explain 90 % of the wind speed variability (R2 ≈0.90). Predictors adding information on width and height ratio and alignment of street canyons with respect to wind direction are suggested for improving model performance. To assess the applicability of any derived model, the results of the CFD model should be thoroughly evaluated against field measurements.
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24. |
- Jonsson, P., et al.
(author)
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Longwave incoming radiation in the Tropics: results from field work in three African cities
- 2006
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In: Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 85:3-4, s. 185-201
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Journal article (peer-reviewed)abstract
- This study investigates differences in longwave incoming radiation (L down arrow) within and between three African cities, Dar es Salaam (Tanzania), Ouagadougou (Burkina Faso), and Gaborone (Botswana), during the dry season, and evaluates the performance of a model to simulate these fluxes. In each city, direct observations of L down arrow, shortwave incoming radiation (K down arrow), air temperature, air humidity, and total suspended particle (TSP) concentration for three land uses (CBD, green residential, and traditional residential) were taken. The observed L down arrow flux decreases with increasing latitude, and temperature becomes an increasingly important factor in governing L down arrow variations further from the Equator. Humidity, as well as particle loading, differs significantly between the three cities. Differences between observed and modelled epsilon(sky) for rural stations near all cities showed a clear diurnal variation, with maximum differences of 0.08 between day and night. This diurnal difference was incorporated in the model and, for urban areas the model overestimates L down arrow by around 25m(-2). However, this model performs equally well regardless of the land use considered in any of the cities. The residual (difference between observed and modelled urban L down arrow) did not show any correlation with particulate pollution. However, the difference between observed and calculated epsilon(sky) is around 0.05 higher in Ouagadougou compared to the other cities, likely due to the heavy dust load observed here. It is concluded that tropical urban longwave radiation is not dramatically different from the mid latitudes.
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25. |
- Kang, Jian, et al.
(author)
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What is the link between temperature and Carbon Dioxide levels? A Granger Causality analysis based on ice core data
- 2014
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In: Journal of Theoretical and Applied Climatology. - Springer : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 116:3-4, s. 537-548
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Journal article (peer-reviewed)abstract
- We use statistical methods to analyze whether there exists long-term causality between temperature and carbon dioxide concentration. The analysis is based on a the Vostok Ice Core data from 400,000 to 6,000 years ago, extended by the EPICA Dome C data which go back to 800,000 years ago. At first, to make the data equidistant, we reconstruct it by linear interpolation. Then, using an approximation of a piecewise exponential function, we adjust for a deterministic trend. Finally, we employ the Granger causality test. We are able to strongly reject the null hypothesis that carbon dioxide concentration does not Granger cause temperature as well as the reverse hypothesis that temperature does not Granger cause carbon dioxide concentration.
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26. |
- Karlsson, Karl-Göran
(author)
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Cloud climate investigations in the Nordic region using NOAA AVHRR data
- 1997
-
In: Theoretical and Applied Climatology. - 0177-798X. ; 57:3-4, s. 181-195
-
Journal article (peer-reviewed)abstract
- A method to estimate monthly cloud conditions (monthly cloud frequencies) from multispectral satellite imagery is described. The operational cloud classification scheme SCANDIA (the SMHI Cloud ANalysis model using DIgital AVHRR data), based on high resolution imagery from the polar orbiting NOAA-satellites, has been used to produce monthly cloud frequencies for the entire year of 1993 and some additional months in 1991, 1992, 1994 and 1995. Cloud analyses were made for an area covering the Nordic countries with a horizontal resolution of four km. Examples of seasonal, monthly and diurnal variation in cloud conditions are given and an annual mean for 1993 is presented. Comparisons with existing surface observations showed very good agreement for horizontal cloud distributions but approximately 5% smaller cloud amounts were found in the satellite estimations. The most evident problems were encountered in the winter season due to difficulties in identifying low-level cloudiness at very low sun elevations. The underestimation in the summer season was partly fictious and caused by the overestimation of convective cloud cover by surface observers. SCANDIA results were compared to ISCCP (International Satellite Cloud Climatology Project) cloud climatologies for two selected months in 1991 and 1992. ISCCP cloudiness was indicated to be higher, especially during the month with anticyclonic conditions where a cloudiness excess of more than 10% were found. The regional variation of cloud conditions in the area was found to be inadequately described by ISCCP cloud climatologies. An improvement of the horizontal resolution of ISCCP data seems necessary to enable use for regional applications. The SCANDIA model is proposed as a valuable tool for local and regional monitoring of the cloud climatology at high latitudes. More extensive comparisons with ISCCP cloud climatologies are suggested as well as comparisons with modelled cloudiness from atmospheric general circulation models and climate models. Special studies of cloud conditions in the Polar areas are also proposed.
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27. |
- Khidher, Salar Ali, et al.
(author)
-
The effect of the North Atlantic Oscillation on the Iraqi climate 1982-2000
- 2015
-
In: Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 1434-4483 .- 0177-798X. ; 122:3-4, s. 771-782
-
Journal article (peer-reviewed)abstract
- In this study, we have analyzed the spatial and temporal correlation between the North Atlantic Oscillation (NAO) and the climate in Iraq, with a focus on precipitation, temperature, and number of Mediterranean cyclones. It was found that the influence of the NAO varies per climate indicator. For example, the influence is greater on precipitation than on temperature. One conclusion of the study is that the mean annual precipitation in Iraq increases during a negative phase of the NAO and decreases during a positive phase. In addition, the correlation between NAO and precipitation is more pronounced in the south of the country than in the middle and northern regions. Regarding the temporal correlation between NAO and precipitation, the influence of the NAO on Iraqi precipitation was found to be weak during the fall season, but to become more pronounced in the winter, culminating during the spring, and then vanishing in the summer. It was also concluded that when the NAO is in a positive phase, the area featuring a desert climate (Bwha) expands in Iraq, while the area featuring other climates decreases. During these years, both the Mediterranean climate (Csa) and the steppe climate (Bsha) cover a smaller part of the country due to the limited amount of precipitation. The opposite occurs during a negative phase of the NAO. Analysis of the number of Mediterranean cyclones that reach Iraq shows that there is no significant difference in the number of cyclones occurring during negative and positive phases of the NAO. However, there are differences in the strength of the cyclones. This study represents a first step in analyzing the relation between the NAO and the Iraqi climate and hopes to lead to further research.
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28. |
- Kizza, Michael, et al.
(author)
-
Temporal rainfall variability in the Lake Victoria Basin in East Africa during the twentieth century
- 2009
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In: Journal of Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 98:1-2, s. 119-135
-
Journal article (peer-reviewed)abstract
- Water resources systems are designed and operated on assumption of stationary hydrology. Existence of trends and other changes in the data invalidates this assumption, and detection of the changes in hydrological time series should help us revise the approaches used in assessing, designing and operating our systems. In addition, trend and step change studies help us understand the impact of man’s activities (e. g. urbanisation, deforestation, dam construction, agricultural activities, etc.) on the hydrological cycle. Trends and step changes in the seasonal and annual total rainfall for 20 stations in the Lake Victoria basin were analysed. The seasonal rainfall for any station in a given year was defined in two ways: (1) fixed time period where the rainy seasons were taken as occurring from March-May (long rains) and from October-December (short rains); and (2) variable periods where the rainy seasons were taken as the three consecutive months with maximum total rainfall covering the period of January-June (long rains) and July-December (short rains), to take into account the fact that the onset of rainy seasons within the basin varies from year to year and from one station to the next. For each station, sub datasets were derived covering different periods (all available data at the station, 1941-1980, 1961-1990, 1971-end of each station’s time series). The trends were analysed using the Mann-Kendall method, while the step changes were analysed using the Worsley Likelihood method. The results show that positive trends predominate, with most stations showing trend being located in the northern part of the basin, though this pattern is not conclusive. In all, 17% of the cases have trends, of which 67% are positive. The 1960s represent a significant upward jump in the basin rainfall. Seasonal rainfall analysis shows that the short rains tend to have more trends than the long rains. The impact of the varying month of onset of the rainy season is that the results from analyzing the fixed-period and variable-period time series are rarely the same, meaning the two series have different characteristics. It may be argued that the variable-period time series are more reliable as a basis for analysing trends and step changes, since these time series reflect more closely the actual variability in rainy seasons from one year to the next. The fixed-period analysis would, on the other hand, find more practical use in planning.
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29. |
- Konarska, Janina, 1986, et al.
(author)
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Transmissivity of solar radiation through crowns of single urban trees—application for outdoor thermal comfort modelling
- 2014
-
In: Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 117:3-4, s. 363-376
-
Journal article (peer-reviewed)abstract
- Trees play an important role in mitigating heat stress on hot summer days, mainly due to their ability to provide shade. However, an important issue is also the reduction of solar radiation caused by trees in winter, in particular at high latitudes. In this study, we examine the transmissivity of total and direct solar radiation through crowns of single street trees in Göteborg, Sweden. One coniferous and four deciduous trees of species common in northern European cities were selected for case study. Radiation measurements were conducted on nine clear days in 2011–2012 in foliated and leafless tree conditions using two sunshine pyranometers— one located in shade of a tree and the other one on the roof of an adjacent building. The measurements showed a significant reduction of total and direct shortwave radiation in the shade of the studied trees, both foliated and leafless. Average transmissivity of direct solar radiation through the foliated and defoliated tree crowns ranged from 1.3 to 5.3 % and from 40.2 to 51.9 %, respectively. The results confirm the potential of a single urban tree to reduce heat stress in urban environment. However, the relatively low transmissivity through defoliated trees should be considered while planning street trees in high latitude cities, where the solar access in winter is limited. The results were used for parameterisation of SOLWEIG model for a better estimation of the mean radiant temperature (Tmrt). Measured values of transmissivity of solar radiation through both foliated and leafless trees were found to improve the model performance.
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30. |
- Kovács, Attila, et al.
(author)
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Adjustment of the thermal component of two tourism climatological assessment tools using thermal perception and preference surveys from Hungary
- 2016
-
In: Journal of Theoretical and Applied Climatology. - : Springer Vienna. - 0177-798X .- 1434-4483. ; 125:1-2, s. 113-130
-
Journal article (peer-reviewed)abstract
- This study introduces new methodological concepts for integrating seasonal subjective thermal assessment patterns of people into the thermal components of two tourism climatological evaluation tools: the Tourism Climatic Index (TCI) and the Climate-Tourism/Transfer-Information-Scheme (CTIS). In the case of the TCI, we replaced the air temperature and relative humidity as the basis of the initial rating system with the physiologically equivalent temperature (PET)—a complex human biometeorological index. This modification improves the TCI’s potential to evaluate the thermal aspects of climate. The major accomplishments of this study are (a) the development of a new, PET-based rating system and its integration into the thermal sub-indices of the TCI and (b) the regionalization of the thermal components of CTIS to reflect both the thermal sensation and preference patterns of people. A 2-year-long (2011–2012) thermal comfort survey conducted in Szeged, Hungary, from spring to autumn was utilized to demonstrate the implementation of the introduced concepts. We found considerable differences between the thermal perception and preference patterns of Hungarians, with additional variations across the evaluated seasons. This paper describes the proposed methodology for the integration of the new seasonal, perception-based, and preference-based PET rating systems into the TCI, and presents the incorporation of new PET thresholds into the CTIS. In order to demonstrate the utility of the modified evaluation tools, we performed case study climate analyses for three Hungarian tourist destinations. The additional adjustments introduced during the course of those analyses include the reduction of TCI’s temporal resolution to 10-day intervals and the exclusion of nocturnal and winter periods from the investigation.
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31. |
- Kundzewicz, Z. W., et al.
(author)
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Impacts of climate extremes on activity sectors : stakeholders' perspective
- 2008
-
In: Journal of Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 93:02-jan, s. 117-132
-
Journal article (peer-reviewed)abstract
- Significant changes in the climatic system have been observed, which may be attributed to human-enhanced greenhouse effect. Even stronger changes are projected for the future, impacting in an increasing way on human activity sectors. The present contribution, prepared in the framework of the MICE (Modelling the Impact of Climate Extremes) Project of the European Union, reviews how climate change may impact on winter tourism in the Alpine region, intense precipitation and flood potential in central Europe, forest damage in Scandinavia and beach holidays in the Mediterranean coast. Impacts are likely to be serious and largely adverse. Due to a lack of adequate information and lack of broadly accepted and reliable mathematical models describing the impact of changes in climate extremes on these activity sectors, it has been found useful to use expert judgement based impact assessment. Accordingly, regional mini-workshops were organized serving as platforms for communication between scientists and stakeholders, vehicles for dissemination of the state-of-the-art of the scientific understanding and for learning stakeholders' view on extreme events, their impacts and the preparedness system. Stakeholders had the opportunity to react to the scientific results and to reflect on their perception of the likely impacts of projected changes in extremes on relevant activity sectors and the potential to adapt and avert adverse consequences. The results reported in this paper present the stakeholders' suggestions for essential information on different extreme event impacts and their needs from science.
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32. |
- Larsson, Rolf, 1962-, et al.
(author)
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What is the link between temperature, carbon dioxide and methane? : A multivariate Granger causality analysis based on ice core data from Dome C in Antarctica
- 2023
-
In: Journal of Theoretical and Applied Climatology. - : Springer Nature. - 0177-798X .- 1434-4483. ; 153:1-2, s. 49-55
-
Journal article (peer-reviewed)abstract
- This paper continues the work of Kang and Larsson Theoretical and Applied Climatology 116:537-548 (2014) What is the link between temperature and carbon dioxide levels? A Granger causality analysis based on ice core data. Theoretical and Applied Climatology 116:537-548, by adding methane to the study of causality between temperature and carbon dioxide. The data used goes 800,000 years back in time which is possible due to it being extracted from ice cores located at Dome C in Antarctica. First we use linear interpolation to make the three data sets equidistant to be able to employ statistical methods. We adjust for a deterministic trend and find the best model fit to be an autoregressive model with lag two and a piecewise quadratic trend. By employing multivariate Granger causality tests we find strong evidence that temperature, carbon dioxide and methane all Granger cause each other in both directions i.e. carbon dioxide Granger causes temperature and temperature Granger causes carbon dioxide, etc. This is in accordance with the findings of Kang and Larsson, with the extension that we can add methane to establish a trivariate feedback system between temperature, carbon dioxide and methane.
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33. |
- Latif, Muhammad, et al.
(author)
-
Spatiotemporal analyses of temperature and equivalent temperature and their relationship with crop health across Pakistan’s cropland
- 2024
-
In: Journal of Theoretical and Applied Climatology. - 0177-798X .- 1434-4483. ; 155, s. 3473-3491
-
Journal article (peer-reviewed)abstract
- Spatiotemporal variations in temperature (T) and equivalent temperature (Te) significantly impact agricultural production across Pakistan, highlighting the need for enhanced weather and climate modeling. This study utilized four reanalysis datasets spanning a 38-year period (1981–2018): the fifth-generation European Center for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalysis (ERA5), Interim ECMWF reanalysis (ERA-Interim), Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA2), and the Japanese 55-year reanalysis (JRA55). We employed National Oceanic and Atmospheric Administration/Advanced Very High-Resolution Radiometer (NOAA/AVHRR) Normalized Difference Vegetation Index (NDVI) data, a proxy for crop health, to assess the relationship between T, Te, and NDVI. This relationship is examined via regression and correlation analyses, and significance is assessed using the Mann–Kendall test and t-test. Our results show that near-surface T significantly contributes to the magnitude of Te (> 90%), whereas specific humidity (SH) has a smaller impact (< 10%). Both T and Te increase significantly across the entire tropospheric column, at 0.15 – 0.31 and 0.38 – 0.77 °C/decade, respectively. Notably, the mid-tropospheric level exhibits less warming than the upper and lower tropospheric levels. Correlation analyses of T and Te with NDVI reveal that Te exhibits a significantly stronger relationship with NDVI compared to T on both seasonal and annual timescales. The highest correlation occurs in the warm and humid summer monsoon (June – August), with Te showing a correlation of 0.50 and T correlating at 0.22 with NDVI. This study suggests that Te can serve as an additional metric for analysing near-surface heating trends in relation to crop health.
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34. |
- Lindberg, Fredrik, 1974, et al.
(author)
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Urban storage heat flux variability explored using satellite, meteorological and geodata
- 2020
-
In: Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 141, s. 271-184
-
Journal article (peer-reviewed)abstract
- The storage heat flux (Delta Q(S)) is the net flow of heat stored within a volume that may include the air, trees, buildings and ground. Given the difficulty of measurement of this important and large flux in urban areas, we explore the use of Earth Observation (EO) data. EO surface temperatures are used with ground-based meteorological forcing, urban morphology, land cover and land use information to estimate spatial variations of Delta Q(S) in urban areas using the Element Surface Temperature Method (ESTM). First, we evaluate ESTM for four "simpler" surfaces. These have good agreement with observed values. ESTM coupled to SUEWS (an urban land surface model) is applied to three European cities (Basel, Heraklion, London), allowing EO data to enhance the exploration of the spatial variability in Delta Q(S). The impervious surfaces (paved and buildings) contribute most to Delta Q(S). Building wall area seems to explain variation of Delta Q(S) most consistently. As the paved fraction increases up to 0.4, there is a clear increase in Delta Q(S). With a larger paved fraction, the fraction of buildings and wall area is lower which reduces the high values of Delta Q(S).
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35. |
- Lindén, Jenny, 1975, et al.
(author)
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Thermally induced wind patterns in the Sahelian city of Ouagadougou, Burkina Faso.
- 2011
-
In: Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 105:1-2, s. 229-241
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Journal article (peer-reviewed)abstract
- The urban surface wind field in the dry-tropical city of Ouagadougou, Burkina Faso was studied based on data collected at one urban and one suburban station during early dry season. An Intra-Urban Thermal Breeze, creating almost opposite wind directions at the two sites, was found during nights with high atmospheric stability. The high atmospheric stability suggests a decoupling of the surface wind layer from the layer above, allowing the wind system to develop due to the strong intra-urban temperature gradients in the city. Frequent temporary break-downs of the thermal wind system were noticed, generally generating a turn in wind direction towards that of the regional wind, thus indicating a re-coupling with a stronger wind flow in the wind layer above.
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36. |
- Lopez-Moreno, J. I., et al.
(author)
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Air and wet bulb temperature lapse rates and their impact on snowmaking in a Pyrenean ski resort
- 2019
-
In: Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 135:3-4, s. 1361-1373
-
Journal article (peer-reviewed)abstract
- A set of 17 air temperature and relative humidity sensors were used to analyze the temporal variability of surface air temperature (Tair), wet bulb temperature (Twb), and daily snowmaking hours (SM, number of hours per day with Twb<-2 degrees C), lapse rates, and the occurrence of thermal inversions at the Formigal ski resort (Spanish Pyrenees) from December to March during three consecutive ski seasons (2012-2013, 2013-2014, and 2014-2015). The Tair and Twb lapse rates showed strong hourly and daily variability, with both exhibiting almost identical temporal fluctuations.The Twb exhibited average lapse rates that were slightly steeper (-5.2 degrees C/km) than those observed for Tair (-4.9 degrees C/km). The less steep lapse rates and most thermal inversions were observed in December. Days having less (more) steep Tair and Twb lapse rates were observed under low (high) wind speeds and high (low) relative humidity and air pressure. The temporal dynamics of the SM lapse rates was more complex, as this involved consideration of the average Tair in the ski resort, in addition to the driving factors of the spatio-temporal variability of Twb. Thus, on a number of cold (warm) days, snowmaking was feasible at all elevations at the ski resort, independently of the slopes of the lapse rates. The SM exhibited an average daily lapse rate of 8.2h/km, with a progressive trend of increase from December to March.Weather types over the Iberian Peninsula tightly control the driving factors of the Tair, Twb, and SM lapse rates (wind speed, relative humidity, and Tair), so the slopes of the lapse rates and the frequency of inversions in relation to elevation for the three variables are very dependent on the occurrence of specific weather types. The less steep lapse rates occurred associated with advections from the southeast, although low lapse rates also occurred during advections from the east and south, and under anticyclonic conditions. The steepest Tair and Twb lapse rates were observed during north and northwest advections, while the steepest rates for SM were observed during days of cyclonic circulation and advections from the northeast.
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37. |
- Lundberg, Angela, et al.
(author)
-
Snow interception evaporation : review of measurement techniques, processes, and models
- 2001
-
In: Journal of Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 70:1-4, s. 117-133
-
Journal article (peer-reviewed)abstract
- A global warming, primarily affecting wintertime conditions at high latitudes will influence the functioning of the boreal forest. The least known term of the winter water-balance equation is evaporation of snow intercepted in forest canopies. Several investigations stress the importance of snow-interception evaporation in coniferous forests and evaporation fractions of gross precipitation as large as 0.2-0.5 have been observed by investigators in Scotland, Canada, and Japan. Evaporation rates as high as 0.56 mm hm1 are reported. The largest differences between the rain and snow interception evaporation processes are the differences in storage. Snow storage (both mass and duration) is often an order of magnitude larger than that for rain. Snow interception changes the canopy albedo although some studies indicate the opposite. Process knowledge is limited because of measurement difficulties but it is known that canopy closure, aerodynamic resistance (ra), and vapour-pressure deficit are important factors. Existing formulations of ra as function of storage location and age cannot fully explain observed differences in evaporation rates. Operationalhydrology and weather models, and GCMs describe snow interception in a very simplified way and might benefit from incorporation of more realistic schemes.
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38. |
- Lundberg, Angela, et al.
(author)
-
Snow measurement techniques for land-surface-atmosphere exchange studies in boreal landscapes
- 2001
-
In: Journal of Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 70:1-4, s. 215-230
-
Journal article (peer-reviewed)abstract
- Snow has been studied widely in hydrology for many decades whereas recent meteorological interest in snow is caused by increased emphasis on high latitudes and wintertime in climate-change research as well as by the need to improve weather-forecast models during these conditions. Ground-based measurements of snow properties are needed both to improve understanding of surface-atmosphere exchange processes and to provide ground truth to new remote-sensing algorithms. This justifies a review of techniques to measure snow in combination with establishment of criteria for the suitability of the methods for process studies. This review assesses the state-of-art in ground-based snow-measurement techniques in the end of the 1990s in view of their accuracy, time resolution, possibility to automate, practicality and suitability in different terrain. Methods for snow-pack water equivalent, depth, density, growth, quality, liquid-water content and water leaving the snow pack are reviewed. Synoptic snow measurements in Fennoscandian countries are widely varying and there is no single standard on which process-related studies can build. A long-term, continuous monitoring of mass and energy properties of a snow cover requires a combination of point-measurement techniques. Areally representative values of snow properties can be achieved through a combination of automatically collected point data with repeated manual, areally covering measurements, remote-sensing data and digital elevation models, preferably in a GIS framework.
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39. |
- Malmgren, Björn, 1942, et al.
(author)
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Oscillatory behavior of monsoon rainfall over Sri Lanka during the late 19(th) and 20(th) centuries and its relationships to SSTs in the Indian Ocean and ENSO
- 2007
-
In: Journal of Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 89:02-jan, s. 115-125
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Journal article (peer-reviewed)abstract
- In this study, we have analyzed the temporal oscillations of precipitation in meso-scale zones of Sri Lanka to examine potential existence of periodic oscillatory behavior in rainfall. Only a few statistically significant cycles were identified: a 3.5-year cycle in most of central Sri Lanka during the January-March rainfall regime and a cycle of the same length in southwestern Sri Lanka during the October regime. A 2.1-year cycle marks the northeastern parts of Sri Lanka during the December/April contrast rainfall regime. This cycle is shown to be strongly related to Quasi-Biennial Oscillation. October and November rainfall are found to be coupled with ENSO fluctuations, and on average, more than 900mm more rainfall is observed per month over all stations during El Nifio than during La Nina years. Analysis of relationships between the observed meso-scale rainfall regions and the Sea Surface Temperatures (SSTs) in the Indian Ocean north of the Equator showed that the northern Indian Ocean can be divided into three particular regions based on similarity in the SST fluctuations: (a) a region with cool upwelling water, (b) non upwelling water, and (c) the Indian Ocean Warm Pool. We found that there are no statistically significant relationships between the observed SST regions in the Indian Ocean and the meso-scale precipitation patterns in Sri Lanka.
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40. |
- Martinez Cruz, Adan
(author)
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Implications for the Iranian economy from climate change effects on agriculture-a static computable general equilibrium approach
- 2023
-
In: Theoretical and Applied Climatology. - 0177-798X .- 1434-4483. ; 154, s. 1221–1235-
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Journal article (peer-reviewed)abstract
- Agricultural sectors worldwide are under direct threat from climate change conditions. In Iran, agricultural production has decreased due to droughts originating in an increase in annual maximum temperatures-with the corresponding increase in crop respiration and evapotranspiration-and a decrease in accumulated precipitation. Based on a static computable general equilibrium approach, this paper reports implication for the Iranian economy from the effects of climate change on agriculture--as modeled through three scenarios relying on assumptions about the magnitude of continued reduction in total agricultural production. Reductions of 6%, 12%, and 18% in total agricultural production reasonably cover the range of impacts that climate change is expected to impose on the Iranian agricultural sector--under the assumption that no behavioral adaptations or policy interventions are in place. Our simulations suggest that effects on the Iranian economy imply a reduction in GDP ranging between 3.7 and 6.3%. In addition, 5-17% of labor moves away from the agriculture sector--this labor relocation occurs due to declining agriculture incomes. Findings illustrate that climate change will reduce households' consumption and income in all economic sectors, particularly among rural households. We suggest that policies in Iran should focus on improving cultivation methods to save water resources and alleviate the expected effects of climate change. The current study's outcomes are helpful for policymakers, especially in countries with water scarcity.
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41. |
- Matyasovszky, István, et al.
(author)
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Abrupt temperature changes during the last 1,500 years
- 2013
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In: Journal of Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 112:1-2, s. 215-225
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Journal article (peer-reviewed)abstract
- We investigate the occurrence of abrupt changes in a total of 35 different proxy records from the extra-tropical Northern Hemisphere for the last ~1,500 years. The proxy records include ice-core δ18O, speleothem, tree ring width/density, marine sediment and lake sediment records with annual, sub-decadal or decadal resolutions. The aim is to explore the spatio–temporal distribution of abrupt climate changes using a kink point analysis technique. A clustering of warm kink points (the kink points with the highest temperatures) around AD 1000 appears corresponding to the Medieval Warm Period and indicates a geographically widespread temperature peak at that time. Kink points around AD 1000 are somewhat more numerous on higher latitudes than on lower latitudes. There are some tendencies for the coldest kink points (the kink points with the lowest temperatures) to be clustered in the ninetenth century, but they are generally more unevenly spaced in time than the warm peaks around AD 1000. The relative lack of kink points detected during the 1500 s–1700 s, likely the coldest part of the Little Ice Age, implies that this cold period was relatively stable and without abrupt events. A possible cluster of kink points on lower latitudes in the early ninth century is also found. No clear difference in the timing of kink points between the different proxy types can be observed.
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42. |
- Moderow, Uta, et al.
(author)
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Available energy and energy balance closure at four coniferous forest sites across Europe
- 2009
-
In: Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 1434-4483 .- 0177-798X. ; 98:3-4, s. 397-412
-
Journal article (peer-reviewed)abstract
- The available energy (AE), driving the turbulent fluxes of sensible heat and latent heat at the earth surface, was estimated at four partly complex coniferous forest sites across Europe (Tharandt, Germany; Ritten/Renon, Italy; Wetzstein, Germany; Norunda, Sweden). Existing data of net radiation were used as well as storage change rates calculated from temperature and humidity measurements to finally calculate the AE of all forest sites with uncertainty bounds. Data of the advection experiments MORE II (Tharandt) and ADVEX (Renon, Wetzstein, Norunda) served as the main basis. On-site data for referencing and cross-checking of the available energy were limited. Applied cross checks for net radiation (modelling, referencing to nearby stations and ratio of net radiation to global radiation) did not reveal relevant uncertainties. Heat storage of sensible heat J (H), latent heat J (E), heat storage of biomass J (veg) and heat storage due to photosynthesis J (C) were of minor importance during day but of some importance during night, where J (veg) turned out to be the most important one. Comparisons of calculated storage terms (J (E), J (H)) at different towers of one site showed good agreement indicating that storage change calculated at a single point is representative for the whole canopy at sites with moderate heterogeneity. The uncertainty in AE was assessed on the basis of literature values and the results of the applied cross checks for net radiation. The absolute mean uncertainty of AE was estimated to be between 41 and 52 W m(-2) (10-11 W m(-2) for the sum of the storage terms J and soil heat flux G) during mid-day (approximately 12% of AE). At night, the absolute mean uncertainty of AE varied from 20 to about 30 W m(-2) (approximately 6 W m(-2) for J plus G) resulting in large relative uncertainties as AE itself is small. An inspection of the energy balance showed an improvement of closure when storage terms were included and that the imbalance cannot be attributed to the uncertainties in AE alone.
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43. |
- Mohammed, Ruqayah, et al.
(author)
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Climate change and water resources in arid regions : uncertainty of the baseline time period
- 2019
-
In: Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 137:1-2, s. 1365-1376
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Journal article (peer-reviewed)abstract
- Recent climate change studies have given a lot of attention to the uncertainty that stems from general circulation models (GCM), greenhouse gas emission scenarios, hydrological models and downscaling approaches. Yet, the uncertainty that stems from the selection of the baseline period has not been studied. Accordingly, the main research question is as follows: What would be the differences and/or the similarities in the evaluation of climate change impacts between the GCM and the delta perturbation scenarios using different baseline periods? This article addresses this issue through comparison of the results of two different baseline periods, investigating the uncertainties in evaluating climate change impact on the hydrological characteristics of arid regions. The Lower Zab River Basin (Northern Iraq) has been selected as a representative case study. The research outcomes show that the considered baseline periods suggest increases and decreases in the temperature and precipitation (P), respectively, over the 2020, 2050 and 2080 periods. The two climatic scenarios are likely to lead to similar reductions in the reservoir mean monthly flows, and subsequently, their maximum discharge is approximately identical. The predicted reduction in the inflow for the 2080–2099 time period fluctuates between 31 and 49% based on SRA1B and SRA2 scenarios, respectively. The delta perturbation scenario permits the sensitivity of the climatic models to be clearly determined compared to the GCM. The former allows for a wide variety of likely climate change scenarios at the regional level and are easier to generate and apply so that they could complement the latter.
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44. |
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45. |
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46. |
- Quesada Montano, Beatriz, et al.
(author)
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Characterising droughts in Central America with uncertain hydro-meteorological data
- 2019
-
In: Journal of Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 137:3-4, s. 2125-2138
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Journal article (peer-reviewed)abstract
- Central America is frequently affected by droughts that cause significant socio-economic and environmental problems. Drought characterisation, monitoring and forecasting are potentially useful to support water resource management. Drought indices are designed for these purposes, but their ability to characterise droughts depends on the characteristics of the regional climate and the quality of the available data. Local comprehensive and high-quality observational networks of meteorological and hydrological data are not available, which limits the choice of drought indices and makes it important to assess available datasets. This study evaluated which combinations of drought index and meteorological dataset were most suitable for characterising droughts in the region. We evaluated the standardised precipitation index (SPI), a modified version of the deciles index (DI), the standardised precipitation evapotranspiration index (SPEI) and the effective drought index (EDI). These were calculated using precipitation data from the Climate Hazards Group Infra-Red Precipitation with Station (CHIRPS), the CRN073 dataset, the Climate Research Unit (CRU), ECMWF Reanalysis (ERA-Interim) and a regional station dataset, and temperature from the CRU and ERA-Interim datasets. The gridded meteorological precipitation datasets were compared to assess how well they captured key features of the regional climate. The performance of all the drought indices calculated with all the meteorological datasets was then evaluated against a drought index calculated using river discharge data. Results showed that the selection of database was more important than the selection of drought index and that the best combinations were the EDI and DI calculated with CHIRPS and CRN073. Results also highlighted the importance of including indices like SPEI for drought assessment in Central America.
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47. |
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48. |
- Rayner, D.P. 1973, et al.
(author)
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A statistical downscaling algorithm for thermal comfort applications
- 2015
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In: Journal of Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 122:3-4, s. 729-742
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Journal article (peer-reviewed)abstract
- We describe a new two-step modeling framework for investigating the impact of climate change on human comfort in outdoor urban environments. In the first step, climate change scenarios for air temperature and solar radiation (global, diffuse, direct components) are created using a change-factor algorithm. The change factors are calculated by comparing ranked daily regional climate model outputs for a future-period and a present-day period, and then changes consistent with these daily change factors are applied to historical hourly climate observations. In the second step, the mean-radiant-temperature (Tmrt) is calculated using the SOLWEIG (SOlar and LongWave Environmental Irradiance Geometry) model. Tmrt, which describes the radiant heat exchange between a person and their surroundings, is one of the most important meteorologically derived parameters governing human energy balance and outdoor thermal comfort, especially during warm and sunny days.We demonstrate that change factors can be applied independently to maximum air temperature and daily global solar radiation, and show that the outputs from the algorithm, when aggregated to daily values, are consistent with the driving regional climate model. Finally, we demonstrate how to obtain quantitative information from the scenarios regarding the potential impact of climate change on outdoor thermal comfort, by calculating changes in the distribution of hourly summer day-time Tmrt and changes in the number of hours with Tmrt >55 °C.
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49. |
- Rimkus, Egidijus, et al.
(author)
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Scots pine radial growth response to climate and future projections at peat and mineral soils in the boreo-nemoral zone
- 2019
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In: Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 136:1-2, s. 639-650
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Journal article (peer-reviewed)abstract
- This paper aims to study what influence different meteorological parameters have on the radial tree growth of Scots pine (Pinus sylvestris L.) in peat and mineral soils, as well as to make predictions of radial tree growth responses to changing climate based on various future climate projections. Four Lithuanian peatland complexes representing different geographical settings and hydrological conditions were studied. From each study site, two tree-ring width (TRW) series were derived, one from trees growing on peat soil and one from trees on mineral soil at the periphery of the peatland. The annual growth rings from trees grown on mineral soils, in different geographical regions in Lithuania, show synchronicity, whereas the correlation between the TRW series from different peatland sites was weak to absent. The main factor that explains radial tree growth at the mineral-soil sites was air temperature during early spring (February–March), which influences the onset and duration of the growing season. However, variations in radial tree growth on the peatland sites were also attributed to lagged hydrological responses relating to precipitation and evaporation over several years. Our future projections show that growth conditions for pine trees on mineral soils will improve in the twenty-first century in Lithuania following an increase of air temperature in early spring. The predictions for the trees growing on peat soils, however, rely on the groundwater-level changes governed by a combination of precipitation and evaporation changes. Towards the end of the twenty-first century, the groundwater level in most Lithuanian peatlands is expected to increase, which most likely will result in harsher growth conditions for the peatland trees. This assumption is, however, open for debate as the peatland trees appear to favour the current warming conditions. It may therefore be too early to precisely predict future growth responses for the peatland trees, but this study is a next step to better understand future climate dynamics and vegetation responses in the Baltic region.
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50. |
- Rivera, Diego, et al.
(author)
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Forecasting monthly precipitation in Central Chile: a self-organizing map approach using filtered sea surface temperature
- 2012
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In: Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 1434-4483 .- 0177-798X. ; 107:1-2, s. 1-13
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Journal article (peer-reviewed)abstract
- Western South America is subject to considerable inter-annual variability due to El Nio-Southern Oscillation (ENSO) so forecasting inter-annual variations associated with ENSO would provide an opportunity to tailor management decisions more appropriately to the season. On one hand, the self-organizing maps (SOM) method is a suitable technique to explore the association between sea surface temperature and precipitation fields. On the other hand, Wavelet transform is a filtering technique, which allows the identification of relevant frequencies in signals, and also allows localization on time. Taking advantage of both methods, we present a method to forecast monthly precipitation using the SOM trained with filtered SST anomalies. The use of the SOM to forecast precipitation for Chillan showed good agreement between forecasted and measured values, with correlation coefficients (r (2)) ranging from 0.72 to 0.91, making the combined use filtered SST fields and SOM a suitable tool to assist water management, for example in agricultural water management. The method can be easily tailored to be applied in other stations or to other variables.
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