| 1. |
- Holst, Jutta, et al.
(författare)
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Effect of meteorological exchange conditions on PM10 concentration
- 2008
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Ingår i: Meteorologische Zeitschrift. - : Schweizerbart. - 1610-1227 .- 0941-2948. ; 17:3, s. 273-282
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Tidskriftsartikel (refereegranskat)abstract
- The short-term limit value for PM10 having become effective in January 2005 was exceeded in many regions within the EU in 2005 and 2006. Therefore, strategies, particularly with respect to traffic control, are discussed, which could cause reduced PM10 concentrations leading to a more effective compliance with the short-term PM10 limit value. These strategies are often justified on PM10 differences between a roadside and an adjacent urban background station. As PM10 is a complex mixture of species originating from different sources, the working hypothesis has been posted that the meteorological exchange conditions strongly affect the PM10 concentration. Therefore, the role of the meteorological exchange conditions with respect to different PM10 patterns, like cycles and PM10 episodes, was investigated on the basis of mean daily PM10 values from air pollution monitoring stations in Baden-Wurttemberg (SW Germany) in the period January 2001 to February 2006. To characterise the meteorological exchange conditions in a spatial resolution, different meteorological variables were used. Partly, they are directly measured at the air pollution monitoring stations or, as for the height of the mixing-layer (MLH) and the stagnation index (SI), they were derived from results of the local model (LM) of the German Weather Service. For periods without precipitation, the results show a statistically significant relationship between PM10 and MLH as well as SI. PM10 increased with decreasing MLH and increasing SI. During periods with precipitation, these relationships were very weak and had no statistical significance. The analysis of the influence of precipitation performed on a daily basis revealed a distinct reduction of PM10 on the first day with precipitation after a period without precipitation. On following days without precipitation, PM10 increased again. Characteristic of the PM10 episodes analysed were remarkably reduced meteorological exchange conditions described by MLH, near-surface wind speed and precipitation. As a case study, two extreme PM10 episodes in January/February 2006 were investigated in detail. As expected, the station-specific variability of the mean daily PM10 values correlated well with daily values of MLH and SI reflecting the pattern of the regional meteorological exchange conditions. Altogether, all results of this investigation point out the main significance of the meteorological exchange conditions on the PM10 level, which is particularly dominant during PM10 episodes.
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| 2. |
- Roegnvaldsson, Olafur, et al.
(författare)
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Numerical simulations of precipitation in the complex terrain of Iceland - Comparison with glaciological and hydrological data
- 2007
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Ingår i: Meteorologische Zeitschrift. - : Schweizerbart. - 1610-1227 .- 0941-2948. ; 16:1, s. 71-85
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric flow over Iceland has been simulated for the period September 1987 through June 2003, using the PSU/NCAR MM5 mesoscale model driven by initial and boundary data from the European Centre for Medium-range Weather Forecasts (ECMWF). The simulated precipitation is compared with two types of indirect precipitation observations. Firstly, snow accumulation on two large ice caps in SE-Iceland and on two large glaciers in central Iceland. Secondly, model output is used as input to the WaSiM-ETH hydrological model to calculate and compare the runoff with observed runoff from six watersheds in Iceland for the water years 1987-2002. Model precipitation compares favourably with both types of validation data. The seasonal and inter-annual variability of precipitation is investigated at low as well as high altitudes. The simulations reveal a negative trend in the winter precipitation in W-Iceland, but a positive trend in the ratio of lowland precipitation to mountain precipitation in E-Iceland. There is in general a substantial inter-annual variability in the ratio of lowland precipitation to precipitation in the mountains, especially in E-Iceland, emphasizing the limitation of precipitation observations in the lowlands as a proxy for precipitation in the mountains. In order to assess the impact of orography on the precipitation climate of Iceland, precipitation is simulated with flat Iceland and compared to a simulation with true orography. It is found that the mountains contribute to a total increase of precipitation in Iceland of the order of 40 %.
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| 3. |
- Pleijel, Håkan, 1958
(författare)
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Concentration gradients of ozone and other trace gases in and above cereal canopies
- 2008
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Ingår i: Meteorologische Zeitschrift. - : Schweizerbart. - 0941-2948. ; 17:2, s. 187-192
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Tidskriftsartikel (refereegranskat)abstract
- The concentration of ozone (O-3) above and within a barley canopy and a wheat canopy was studied. Compared to the concentration at 1.1 m above the ground (0.1 m above the 1 m tall canopy), the concentration within the canopy (0.3 m above ground) was typically reduced by approximately 20 % during the day and 40 % during the night for both barley and wheat, reflecting the slower mixing of air in the lower wind speeds of the night. The variation in ozone reduction in the canopy during the hours with the highest average wind speeds (11:00-16:00) could partly be explained by the effect of vapour pressure deficit on stomatal conductance. The concentration gradients of nitrogen dioxide (NO2) above and into the canopy were weaker but similar to that of O-3 while the measurements suggested emission of nitric oxide (NO). During the day the carbon dioxide (CO2) concentration had a local minimum at the top of the canopy reflecting the photosynthesis activity of the sunlit, non-senescent part of the canopy, while during the night very high concentrations of CO2 were observed within and immediately above the canopy as a result of respiration in combination with limited air mixing. Inside open-top chambers no concentration gradients of O-3 into the canopy or horizontally above the canopy could be detected.
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| 4. |
- Rutgersson, Anna, et al.
(författare)
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Impact of surface waves in a regional climate model
- 2010
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Ingår i: Meteorologische Zeitschrift. - : Schweizerbart. - 0941-2948 .- 1610-1227. ; 19:3, s. 247-257
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Tidskriftsartikel (refereegranskat)abstract
- A coupled regional atmosphere-wave model system is developed with the purpose of investigating the impactof climate changes on the wave field, as well as feed-back effects of the wave field on the atmosphericparameters. This study focuses on the effects of introducing a two-way atmosphere-wave coupling on theatmosphere as well as on wave parameters. The model components are the regional climate model RCA, andthe third generation wave modelWAM. Two different methods are used for the coupling, using the roughnesslength and only including the effect of growing sea, and using the wave age and introducing the reductionof roughness due to decaying sea (swell). Introducing a two-way coupling results in an altered frequencydistribution of wind speed and wave heights. When only including growing sea the impact of waves on thelong term mean atmospheric parameters is limited, inducing a reduction of wind speed and significant waveheight. When also the impact of swell is introduced, there is a shift towards higher wind speeds as well ashigher significant wave heights in the four investigated areas. There is a reduction of surface heat fluxesand a decrease in near surface temperature as well as a significant increase in near surface humidity. Themajor conclusion is that when introducing a more realistic surface description over sea, the air-sea interactionrepresented by waves has a significant impact also on long term averages of parameters in the atmosphere.Waves should thus be introduced in climate models for a realistic description of processes over sea.
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| 5. |
- Durán, Pablo, et al.
(författare)
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Meso-microscale coupling for wind resource assessment using averaged atmospheric stability conditions
- 2019
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Ingår i: Meteorologische Zeitschrift. - : Schweizerbart science publishers. - 0941-2948 .- 1610-1227. ; 28:4, s. 273-291
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Tidskriftsartikel (refereegranskat)abstract
- A methodology to couple Numerical Weather Prediction (NWP) models with steady-state Computational Fluid Dynamic (CFD) models for wind resource assessment applications is proposed. NWP simulations are averaged according to their atmospheric stability and wind direction. The averaged NWP simulations are used to generate the initial and boundary conditions of the CFD model. The method is applied using one year of Weather Research and Forecasting (WRF) simulations at the Honkajoki wind farm in Finland and validated by Sonic Detection and Ranging (SODAR) measurements at the site. It is shown that coupled simulations reproduce a more realistic shear for heights above 150 m. In terms of estimated energy production, there is not a big difference between coupled and standalone models. Nevertheless, a considerable difference in the horizontal wind speed patterns can be seen between the coupled and non-coupled approaches. The WRF model resolution has only a small influence on the coupled CFD results.
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| 6. |
- Omstedt, Anders, et al.
(författare)
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Closing the water and heat cycles of the Baltic Sea
- 2000
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Ingår i: METEOROLOGISCHE ZEITSCHRIFT. - 0941-2948. ; 9:1, s. 59-66
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Tidskriftsartikel (refereegranskat)abstract
- The objective of the present paper is to analyze the water and heat cycles of the Baltic Sea. The closure equations fur the water and heat cycles are formulated and the appropriate fluxes are calculated using the ocean model PROBE-Baltic forced by meteoro
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| 7. |
- Persson, Ylva, et al.
(författare)
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Effects of intra-genotypic variation, variance with height and time of season on BVOC emissions
- 2016
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Ingår i: Meteorologische Zeitschrift. - : Schweizerbart. - 1610-1227 .- 0941-2948. ; 25:4, s. 377-388
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Tidskriftsartikel (refereegranskat)abstract
- Biogenic Volatile Organic Compounds (BVOCs) are trace gases other than CO2 and CH4 produced and emitted by the biosphere, where the amounts released depend on climatic factors such as temperature and solar irradiation. However, interpretation of leaf-level measurements is currently hampered by factors such as large within-genotypic variability, measurement height and time in the season. A campaign was performed between June and August in 2013 in Taastrup, Denmark to study these uncertainties. BVOC emissions were measured from leaves and needles at heights of 2 m, 5.5m and 12.5m in the canopy and for seven trees; four Norway spruces (Picea abies) of which two trees had a budburst approximately a week before the other two, two English oaks (Quercus robur) and one European beech (Fagus sylvatica). Differences in chemical composition and emission strength between June and August were observed between the different trees. English oak's main compound isoprene increased from 62-74%of the total emission in June to approximately 97% in August, which is linked to leaf development over the summer season. The total emission from all measured spruce trees decreased from July to August, but without a loss in the diversity of emitted compounds. The trees showed indications of drought stress as there was a period without precipitation lasting 21 days during the study. There were no differences in emission patterns within all of the measured Norway spruces. For measurement height, there was only a significant difference in emission pattern for European beech as the top of the canopy emitted 7-9 times more in relation to lower canopy levels. Our results suggest there was little within-genotype variability and the wide spacing between trees had an influence on the individual emission patterns. These results are important in order to understand the significance of within-genotypic variation, canopy height and seasonal development in relation to the emission patterns of the selected species. Furthermore, it will provide helpful insights for modelers who wish to improve their emission estimates.
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