| 1. |
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| 2. |
- Boman, Johan, 1955, et al.
(author)
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A tentative study of urban and suburban fine particles (PM2.5) collected in Ouagadougou, Burkina Faso
- 2009
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In: X-Ray Spectrometry. - : Wiley. - 0049-8246 .- 1097-4539.
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Journal article (peer-reviewed)abstract
- The aim of the study was to determine the mass, black carbon (BC), and elemental concentrations in fine particles (PM2.5) and their variations at two sites in Ouagadougou, the capital city of Burkina Faso. The weather situation in Ouagadougou during the field campaign was dominated by high pressure with variable cloudiness and no precipitation. Diurnal temperatures varied between 19 and 38 °C and relative humidity between 10 and 60%. Winds in Ouagadougou were generally coming in from the north, showing a diurnal pattern with gusts of up to 6 m/s during daytime, while evenings and nights were calmer with very stable atmospheric conditions. However, during part of this field campaign, a period of nighttime moderately stable atmospheric conditions occurred with increased wind speed and more easterly winds. Cyclones were used for the PM2.5 particle collection at both sites. The elemental analysis was done using energy dispersive x-ray fluorescence (EDXRF) spectroscopy. Cl, K, Ca, Ti, Mn, Fe, Cu, Zn, Br, Rb, Sr, and Pb were identified and quantified in most of the samples. The particle mass concentration was 27-164 µg/m3 while BC varied between 1.3 and 8.2 µg/m3. No influence of leaded gasoline was found. Soil dust was identified as a major component of the particles, which was confirmed by comparing with the elements in a soil sample. A significant difference in elemental, BC, and mass concentrations was seen between periods with very stable and moderately stable atmospheric conditions. Copyright © 2009 John Wiley & Sons, Ltd.
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| 3. |
- Carlström, Eric, 1957, et al.
(author)
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Medical Emergencies During a Half Marathon Race - The Influence of Weather
- 2019
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In: International Journal of Sports Medicine. - Stuttgart : Georg Thieme Verlag KG. - 0172-4622 .- 1439-3964. ; 40:5, s. 312-316
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Journal article (peer-reviewed)abstract
- The aim was to analyze the influence of weather conditions on medical emergencies in a half-marathon, specifically by evaluating its relation to the number of non-finishers, ambulance-required assistances, and collapses in need of ambulance as well as looking at the location of such emergencies on the race course. Seven years of data from the world's largest half marathon were used. Meteorological data were obtained from a nearby weather station, and the Physiological Equivalent Temperature (PET) index was used as a measure of general weather conditions. Of the 315,919 race starters, 104 runners out of the 140 ambulance-required assistances needed ambulance services due to collapses. Maximum air temperature and PET significantly co-variated with ambulance-required assistances, collapses, and non-finishers (R (2) =0.65-0.92; p=0.001-0.03). When air temperatures vary between 15-29 degrees C, an increase of 1 degrees C results in an increase of 2.5 (0.008/1000) ambulance-required assistances, 2.5 (0.008/1000) collapses (needing ambulance services), and 107 (0.34/1000) non-finishers. The results also indicate that when the daily maximum PET varies between 18-35 degrees C, an increase of 1 degrees C PET results in an increase of 1.8 collapses (0.006/1000) needing ambulance services and 66 non-finishers (0.21/1000).
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| 4. |
- Eliasson, Ingegärd, 1961, et al.
(author)
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Diurnal and intra-urban particle concentrations in relation to windspeed and stability during the dry season in three African cities
- 2009
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In: Environmental Monitoring and Assessment. - : Springer Science and Business Media LLC. - 0167-6369 .- 1573-2959. ; 154:1-4, s. 309-324
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Journal article (peer-reviewed)abstract
- The spatial and temporal variations of PM2.5, PM10 and TSP in three African cities of different sizes (Dar es Salaam, Ouagadougou and Gaborone) were investigated using portable particle counters. Three different areas (downtown, green residential and traditional residential) and a reference site were designated in each of the cities in order to detect intra-urban and temporal variability. Morning, noon and night measurements were conducted in the urban areas while observations at reference stations were made continuously over the field periods. A clear diurnal pattern in particle concentrations was found in inland Gaborone and Ouagadougou, with morning and night peaks where the latter was the highest. However, in coastal Dar es Salaam the night peak was almost absent due to delayed stabilisation of the air. Particle concentrations at the Ouagadougou reference station were extreme. The direct contribution of vehicle emissions are of secondary importance since the PM2.5/PM10 ratios are low (0.1–0.3). Much of the particles are supposed to be soil particles that are entrained in the air by daytime high windspeeds followed by nighttime subsidence as the air is stabilised and windspeed decreases. However, in all three cities, resuspension are important as areas with a network of unpaved roads showed the highest concentrations of suspended particles. Generally, the central business district had the lowest concentrations of particulate matter.
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| 6. |
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| 7. |
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| 8. |
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| 9. |
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| 10. |
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| 11. |
- Holmer, Björn, 1943, et al.
(author)
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Evening evapotranspirative cooling in relation to vegetation and urban geometry in the city of Ouagadougou, Burkina Faso
- 2013
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In: International Journal of Climatology. - : Wiley. - 0899-8418. ; 33:15, s. 3089-3105
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Journal article (peer-reviewed)abstract
- Intra-urban cooling in the city of Ouagadougou, capital of Burkina Faso in the Sahel zone of West Africa, was studied during the dry seasons in 2003, 2004 and 2007. The aim was to see how vegetation, built structure and position within the built-up area influenced the nocturnal cooling. Cooling was divided into two phases. In Phase 1 (16:00 -20:00 hours LST = CET), cooling was very different between the sites while in Phase 2 (20:00 -06:00 hours LST), cooling rates differed insignificantly and the whole area cooled almost at the same rate. Thus the temperature differences between the sites developed during these few hours in Phase 1 were preserved during the rest of the night. In Phase 1, Evening Evapotranspirative Cooling was intensive at vegetated sites that cooled almost twice as fast as sparsely vegetated. This was indicated by a humidity rate (increase of specific humidity per hour) that was high at a vegetated site, but considerably lower at a sparsely vegetated. In Phase 2 the humidity rate was slightly negative with little difference between the sites. After a division in vegetated and sparsely vegetated sites built structure (sky view factor) were shown to influence cooling, but no influence of the position within the built-up area was traced. Thus, the site-specific properties dominated cooling, giving large intra-urban temperature differences. The study also showed the importance of considering a large enough source area to account for micro-scale advection.
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| 12. |
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| 13. |
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| 14. |
- Holmer, Björn, 1943, et al.
(author)
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How to transform the standing man from a box to a cylinder – a modified methodology to calculate mean radiant temperature in field studies and models
- 2015
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In: ICUC9 – 9 th International Conference on Urban Climate jointly with 12th Symposium on the Urban Environment. 20-24 July, Toulouse, France.
-
Conference paper (other academic/artistic)abstract
- Mean radiant temperature (Tmrt) has shown to be an important meteorological variable in studies of human comfort and health. The Tmrt is calculated as the surface temperature of a standing man approximated as a cylinder emitting the same amount of longwave radiation as all short- and longwave radiation fluxes received from the surrounding four cardinal points and down- and upwards. The calculation was introduced by Höppe in 1992 and has then been used both in models (e.g. SOLWEIG) and field studies. However, the formula by Höppe describes in fact a man shaped like a box and not a cylinder, which has resulted in some peculiar features noticed in studies of Tmrt such as a secondary daytime minimum and an influence of the orientation of the field equipment. A methodology to change the box man to a cylindrical man is proposed. It will remove the peculiarities that have been observed in earlier studies. The methodology is based on the partition of the observed shortwave fluxes in direct and diffuse radiation. The minimum shortwave radiation of the four cardinal points is used as diffuse radiation since it is monitored by a sensor that is not sunlit. By subtraction of this quantity the horizontal direct fluxes are obtained. Calculation of the resultant flux of the sunlit sensors and adjustment for solar angle gives the direct shortwave radiation. The surface of the standing man (as a cylinder) perpendicular to the direct radiation must be determined and the direct shortwave radiation received by the standing man can be calculated. Then the sum of the shortwave fluxes can be calculated. The diffuse and longwave fluxes can be calculated according to the Höppe formula since they differ little with direction. In the SOLWEIG model the direct shortwave radiation is used as an input. Thus the calculation according to the new methodology is easy to apply, only the solar position needs to be added. The new methodology is tested by model calculations with SOLWEIG and field studies in both high-latitude Gothenburg, Sweden and low-latitude Ouagadougou, Burkina Faso. The secondary minimum disappears. In Gothenburg at a site with SVF=0.95 the noon depression of Tmrt by the Höppe formula was about 2 °C and there was an overestimation of 1.5-1.7 °C two-three hours before and after noon.differences in summer. In Ouagadougou data from an open site (SVF=0.83) in the dry season the differences were slightly smaller. Sites with lower SVF and much reflected direct shortwave radiation differed less from the Tmrt obtained with the Höppe formula.
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| 15. |
- Holmer, Björn, 1943, et al.
(author)
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Urban climatic map studies in Sweden: Gothenburg
- 2015
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In: The Urban Climatic Map: A Methodology for Sustainable Urban Planning. - Milton Park : Taylor and Francis. ; , s. 324-342
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Book chapter (peer-reviewed)
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| 16. |
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| 17. |
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| 18. |
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| 19. |
- Johansson, Lars, 1972, et al.
(author)
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Statistical modelling of pedestrian wind speed using high‐resolution digital surface models
- 2012
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In: The Eight International Conference on Urban Climates. ; :abstract 183
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Conference paper (other academic/artistic)abstract
- Spatial variations of near ground wind speed (2magl) within urban areas are simulated by using a statistical model. The model is built upon the statistical relationship between derivatives extracted from digital surface models characterizing urban geometries (sky view factor, fetch, frontal area index) and wind speed, using statistical regression techniques. The geometric parameters are calculated for a number of urban settings in Gothenburg, Sweden. Wind speed patterns are derived using the three-dimensional microclimate model, ENVI-met. The model closely estimate the wind speed within-the major parts of the model domains such as in squares, and narrow streets as well as canyons perpendicular to the incoming wind direction. However, the output wind speed patterns are largely different from the wind speed simulated by ENVI-met in wide streets and around buildings where wind speed is high. Statistical models, as presented here, would be useful for not only climatologist/ meteorologist but also urban designers to consider wind modes depending on urban geometries and also to estimate thermal comfort influenced by wind.
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| 20. |
- 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
-
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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| 21. |
- Konarska, Janina, 1986, et al.
(author)
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Influence of vegetation and building geometry on the spatial variations of air temperature and cooling rates in a high latitude city
- 2016
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In: International Journal of Climatology. - : Wiley. - 0899-8418 .- 1097-0088. ; 36:5, s. 2379-2395
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Journal article (peer-reviewed)abstract
- The aim of this study was to provide a better understanding of how vegetation and building geometry influence the spatial distribution of air temperature and nocturnal cooling rates (CR) in a high-latitude city. Intra-urban thermal variations were analysed in two seasons (May–September and November–March) and in different weather conditions (clear, calm and cloudy, windy) in Gothenburg, Sweden. Simultaneous air temperature measurements were conducted for 2years (2012–2013) at ten fixed park and street sites characterized by varying type and amount of vegetation, building geometry, openness and surface cover. Several spatial characteristics, including sky view factor (SVF) as well as the cover and volume of buildings and trees, were calculated within circular areas of radii ranging from 10 to 150m. Spatial characteristics were found to explain air temperature distribution in the studied area to a large extent throughout the day and year, in both clear, calm as well as cloudy, windy conditions. The highest correlations were found for weighted calculation areas accounting for the influence of both nearest (10m) and wider (25–150m) surroundings. Park sites remained cooler than built-up areas, with the most pronounced cooling effect (0.8°C) on clear, calm days of the warm season. The most important factor governing CR around sunset was SVF. However, on clear, calm nights of the warm season, they were also enhanced by vegetation, indicating the influence of evapotranspiration. Minimum night-time air temperature was governed mostly by the presence of buildings. Within the street canyon, a daytime cooling and night-time warming effect of a street tree was observed, particularly in the warm season. The study shows the importance of various spatial characteristics describing openness, amount of vegetation and building geometry in analysing intra-urban variations in daytime and night-time air temperature.
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| 22. |
- 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
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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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| 23. |
- Konarska, Janina, 1986, et al.
(author)
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Transpiration of urban trees and its cooling effect in a high latitude city
- 2016
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In: International journal of biometeorology. - : Springer Science and Business Media LLC. - 0020-7128 .- 1432-1254. ; 60:1, s. 159-172
-
Journal article (peer-reviewed)abstract
- An important ecosystem service provided by urban trees is the cooling effect caused by their transpiration. The aim of this study was to quantify the magnitude of daytime and night-time transpiration of common urban tree species in a high latitude city (Gothenburg, Sweden), to analyse the influence of weather conditions and surface permeability on the tree transpiration, and to find out whether tree transpiration contributed to daytime or nocturnal cooling. Stomatal conductance and leaf transpiration at day and night were measured on mature street and park trees of seven common tree species in Gothenburg: Tilia europaea, Quercus robur, Betula pendula, Acer platanoides, Aesculus hippocastanum, Fagus sylvatica and Prunus serrulata. Transpiration increased with vapour pressure deficit and photosynthetically active radiation. Midday rates of sunlit leaves ranged from less than 1 mmol m−2 s−1 (B. pendula) to over 3 mmol m−2 s−1 (Q. robur). Daytime stomatal conductance was positively related to the fraction of permeable surfaces within the vertically projected crown area. A simple estimate of available rainwater, comprising of precipitation sum and fractional surface permeability within the crown area, was found to explain 68 % of variation in midday stomatal conductance. Night-time transpiration was observed in all studied species and amounted to 7 and 20 % of midday transpiration of sunlit and shaded leaves, respectively. With an estimated night-time latent heat flux of 24 W m−2, tree transpiration significantly increased the cooling rate around and shortly after sunset, but not later in the night. Despite a strong midday latent heat flux of 206 W m−2, a cooling effect of tree transpiration was not observed during the day.
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| 24. |
- Konarska, Janina, 1986, et al.
(author)
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Transpiration of urban trees and its impact on nocturnal cooling in Gothenburg, Sweden
- 2015
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In: ICUC9 – 9 th International Conference on Urban Climate jointly with 12th Symposium on the Urban Environment. 20-24 July 2015, Toulouse, France.
-
Conference paper (other academic/artistic)abstract
- One of the ecosystem services provided by urban trees is the cooling effect caused by their transpiration. However, while the transpiration of forest trees has been widely studied, little research has been conducted on the daytime and night-time transpirational cooling effect of mature urban trees. Knowledge about the transpiration of street and park trees and its response to different environmental factors can prove useful in estimating the thermal influence of urban greenery as well as in urban planning and management. The aim of this study is to i) quantify the magnitude and diurnal variation of transpiration of common urban tree species in a high latitude city (Gothenburg, Sweden), ii) analyse the influence of weather conditions and fraction of permeable surfaces within the vertically projected crown area on tree transpiration, and iii) find out whether transpiration of urban trees remains active during the night and therefore contributes to nocturnal cooling. Measurements were conducted on mature street and park trees of seven tree species common in Gothenburg: Tilia europaea (Common lime), Quercus robur (English oak), Betula pendula (Silver birch), Acer platanoides (Norway maple), Aesculus hippocastanum (Horse chestnut), Fagus sylvatica (European beech) and Prunus serrulata (Japanese cherry). Stomatal conductance and leaf transpiration were measured using a LI-6400XT Portable Photosynthesis System (LI-COR Biosciences) at daytime and night-time on warm summer days of 2012-2013 in Gothenburg. Leaf area index (LAI) of the studied trees was measured with a LAI-2200 Plant Canopy Analyser (LI-COR Biosciences) in order to estimate the latent heat flux due to tree transpiration. Leaf transpiration was found to increase with vapour pressure deficit and photosynthetically active radiation, with on average 22% of the midday incoming solar radiation being converted into latent heat flux. Midday rates of sunlit leaves varied between species, ranging from less than 1 mmol m-2 s-1 (B. pendula) to over 3 mmol m-2 s-1 (Q. robur). Daytime stomatal conductance was positively related to the fraction of permeable surfaces within the vertically projected tree crown area. A simple estimate of available rainwater, comprising of precipitation sum and a fractional surface permeability within the tree crown area, was found to explain 68% of variation in midday stomatal conductance. The results indicate that a high fractional surface permeability can minimize the frequency of water stress experienced by urban trees and enhance their transpirational cooling. Night-time transpiration was observed in all studied species and was positively related to daytime tree water use. Nocturnal transpiration amounted to 7% and 20% of midday transpiration of sunlit and shaded leaves, respectively. With an estimated latent heat flux of 27 W m-2, evening tree transpiration enhanced the cooling rates around and 1-2 hours after sunset, but not later in the night. The results of transpiration measurements will be combined with vegetation data derived from LIDAR and LAI measurements to estimate neighbourhood- to city-scale cooling effect provided by urban trees.
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| 25. |
- Lau, Kevin Ka-Lun, 1983, et al.
(author)
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Street geometry design and its effect on mean radiant temperature: A parametric study based on numerical modelling
- 2015
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In: ICUC9 – 9 th International Conference on Urban Climate jointly with 12th Symposium on the Urban Environment. 20-24 July 2015, Toulouse, France.
-
Conference paper (other academic/artistic)abstract
- The spatial variation of hotspots, in terms of their locations and magnitude, is examined in the present study, using the Solar and LongWave Environmental Irradiance Geometry (SOLWEIG) model. The effect of street geometry design parameters such as H/W ratios and street orientations on the radiant heat load are analyzed for three European cities with different regional climatic conditions. Various physical configurations of street trees are examined for their corresponding potential in mitigating the radiant heat load within urban structures. Findings suggest that a dense urban structure (H/W ratio ≥ 2) is capable of reducing radiant heat load at street level. High H/W ratios do not only reduce the magnitude of hotspots, but also changes their spatial distribution. The N-S canyons are found to be more favourable than the E-W canyons since they limit sun exposure to several hours at noon, despite of the diminishing difference between two orientations when H/W ratio increases. Diagonal streets reduce the magnitude of hotspots but increase the areas affected by moderately high mean radiant temperature (Tmrt). NE-SW orientated streets exhibits higher average hourly Tmrt during daytime since they are largely sun-exposed at the hottest time of the day. The highest mitigating effect of street trees is found when they are located in the sunlit areas. The reduction in average Tmrt decreases with increasing H/W ratios but considerable mitigating effect is still observed in the NE-SW orientations. It is also observed that larger tree crowns, even with higher spacing between individual trees, provide better shading than closely placed trees with smaller tree crowns. The present study provides information about the locations and magnitude of hotspots in different urban settings as well as the design of street trees as a mitigation measure to radiant heat load. It helps urban planners and designers to better design neighbourhoods in order to improve pedestrian thermal comfort within urban areas.
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| 26. |
- Lindberg, Fredrik, 1974, et al.
(author)
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Characteristics of the mean radiant temperature in high latitude cities—implications for sensitive climate planning applications
- 2014
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In: International Journal Of Biometeorology. - : Springer Science and Business Media LLC. - 0020-7128 .- 1432-1254. ; 58:5, s. 613-627
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Journal article (peer-reviewed)abstract
- Knowledge of how the mean radiant temperature (T mrt ) is affected by factors such as location, climate and urban setting contributes to the practice of climate sensitive planning. This paper examines how T mrt varies within an urban setting and how it is influenced by cloudiness. In addition, variations of T mrt in three high latitude cities are investigated in order to analyse the impact of geographical context and climate conditions. Results showed large spatial variations between sunlit and shaded areas during clear weather conditions, with the highest values of T mrt close to sunlit walls and the lowest values in the areas shaded by buildings and vegetation. As cloudiness increases, the spatial pattern is altered and the differences are reduced. The highest T mrt under cloudy conditions is instead found in open areas where the proportion of shortwave diffuse radiation from the sky vault is high. A regional comparison between three Swedish coastal cities showed that T mrt during summer is similar regardless of latitudinal location. On the other hand, large differences in T mrt during winter were found. Shadows, both from buildings and vegetation are the most effective measure to reduce extreme values of T mrt . However, extensive areas of shadow are usually not desired within outdoor urban environments at high latitude cities. One solution is to create diverse outdoor urban spaces in terms of shadow and also ventilation. This would provide individuals with access to a choice of thermal environments which they can use to assist their thermal regulation, based on personal needs and desires.
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| 27. |
- Lindberg, Fredrik, 1974, et al.
(author)
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SOLWEIG 1.0 – Modelling spatial variations of 3D radiant fluxes and mean radiant temperature in complex urban settings
- 2008
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In: International Journal of Biometeorology. ; 52, s. 697-713
-
Journal article (peer-reviewed)abstract
- The mean radiant temperature, Tmrt, which sums up all shortwave and longwave radiation fluxes (both direct and reflected) to which the human body is exposed is one of the key meteorological parameters governing human energy balance and the thermal comfort of man. In this paper, a new radiation model (SOLWEIG 1.0), which simulates spatial variations of 3D radiation fluxes and Tmrt in complex urban settings, is presented. The Tmrt is derived by modelling shortwave and longwave radiation fluxes in six directions (upward, downward and from the four cardinal points) and angular factors. The model requires a limited number of inputs, such as direct, diffuse and global shortwave radiation, air temperature, relative humidity, urban geometry and geographical information (latitude, longitude and elevation). The model was evaluated using 7 days of integral radiation measurements at two sites with different building geometries – a large square and a small courtyard in Göteborg, Sweden (57°N) – across different seasons and in various weather conditions. The evaluation reveals good agreement between modelled and measured values of Tmrt, with an overall good correspondence of R 2=0.94, (p<0.01, RMSE=4.8 K). SOLWEIG 1.0 is still under development. Future work will incorporate a vegetation scheme, as well as an improvement of the estimation of fluxes from the four cardinal points.
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| 28. |
- Lindén, Jenny, 1975, et al.
(author)
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Intra-urban air pollution in a rapidly growing Sahelian city
- 2012
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In: Environmental International. - : Elsevier BV. - 0160-4120. ; 40, s. 51-62
-
Journal article (peer-reviewed)abstract
- In this paper we analyze spatial and temporal variations of air pollution (PM1, PM2.5, PM10, CO, NOx, O3, Toluene and Benzene) and climate in areas of different development typology in Ouagadougou, Burkina Faso. Analyses are based on measurements from fixed sites and car traverse measurements during field studies in 2007 and 2010. Large spatial and temporal variations were found, showing a generally poor air quality situation, with extreme levels of PM10, commonly exceeding air quality guidelines of WHO. Pollution levels increase considerably with increased atmospheric stability. Important sources were transported dust and re-suspension of dust from unpaved roads, but also traffic emissions and biomass burning. The spatial variations are examined with focus on effects for variations in potential exposure depending on for example area of residence and daily activity pattern, showing that great differences are likely to exist. Ouagadougou, like most developing countries worldwide, currently experiences an extremely rapid population growth in combination with limited financial means. This is likely to create increasingly harmful air pollution situations for the rapidly growing populations of these areas, and shows an urgent need for increased understanding of the pollution situation as well as development of mitigation strategies.
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| 29. |
- Lindén, Jenny, 1975, et al.
(author)
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Thermally induced wind patterns in the Sahelian city of Ouagadougou, Burkina Faso.
- 2011
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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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| 30. |
- Lindén, Jenny, 1975, et al.
(author)
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Urban climate and air pollution in Ouagadougou, Burkina Faso
- 2012
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Reports (other academic/artistic)abstract
- The report Urban Climate and Air pollution in Ouagadougou, Burkina Faso contains an overview of results from five field studies as well as suggestions for air pollution mitigation strategies suitable for Ouagadougou.
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| 31. |
- Linden, J., et al.
(author)
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Using Land Cover, Population, and Night Light Data for Assessing Local Temperature Differences in Mainz, Germany
- 2015
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In: Journal of Applied Meteorology and Climatology. - : American Meteorological Society. - 1558-8424 .- 1558-8432. ; 54:3, s. 658-670
-
Journal article (peer-reviewed)abstract
- Urban areas are believed to affect temperature readings, thereby biasing the estimation of twentieth-century warming at regional to global scales. The precise effect of changes in the surroundings of meteorological stations, particularly gradual changes due to urban growth, is difficult to determine. In this paper, data from 10 temperature stations within 15 km of the city of Mainz (Germany) over a period of 842 days are examined to assess the connection between temperature and the properties of the station surroundings, considering (i) built/paved area surface coverage, (ii) population, and (iii) night light intensity. These properties were examined in circles with increasing radii from the stations to identify the most influential source areas. Daily maximum temperatures T-max, as well as daily average temperatures, are shown to be significantly influenced by elevation and were adjusted before the analysis of anthropogenic surroundings, whereas daily minimum temperatures T-min were not. Significant correlations (p < 0.1) between temperature and all examined properties of station surroundings up to 1000 m are found, but the effects are diminished at larger distance. Other factors, such as slope and topographic position (e.g., hollows), were important, especially to T-min. Therefore, properties of station surroundings up to 1000 m from the stations are most suitable for the assessment of potential urban influence on T-max and T-min in the temperate zone of central Europe.
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| 32. |
- Mattsson, Eskil, 1981, et al.
(author)
-
Recovery and protection of coastal ecosystems after tsunami event and potential for participatory forestry CDM - examples from Sri Lanka
- 2008
-
In: Ocean & Coastal Management. - : Elsevier BV. - 0964-5691 .- 1873-524X. ; 52:1, s. 1-9
-
Journal article (peer-reviewed)abstract
- By using an integrated approach, tsunami affected land, vegetation and inhabitants were assessed to evaluate the potential to restore and protect coastal land in the context of Kyoto Protocol's Clean Development Mechanism in Hambantota district in the south-eastern part of Sri Lanka. Firstly, assessments of the status of the tsunami affected area were carried out by collecting soil and well water samplings for carbon and salinity analysis. Secondly, identification of potential tree species for carbon sequestration and sustainable development was conducted to determine carbon stock and suitability to grow under the prevailing conditions. In addition, interviews to understand the local people's perception of forest plantations and land use were conducted. The results showed that the resilience process of salt intruded lands from the 2004 Asian tsunami has progressed rapidly with low salinity level in the soils 14 months after the event, while the well water showed evidence of salinity contamination. The carbon stock was highest in natural forests followed by coconut plantations. Land users could envision expanding their present plantations or establish new ones. The barriers were defined as lack of financial investment capital and limited land for extended plantations. If a Clean Development Mechanism project is to be established, the coconut tree was found to be the most appropriate tree species since it has high carbon content, had co-benefits and possesses a salt-tolerant characteristic. Finally, the tsunami event has triggered land users to perceive environmental benefits of protection from mangrove or other adequate vegetation such as coconut plantations as welcome and desired to decrease their vulnerability. The assessment of multi-functionality of forest plantations, such as small-scale community based Clean Development Mechanism, its generated income from carbon credits as well as the wish for environmental protection should be considered to increase the attractiveness of plantation projects in the coastal areas.
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| 33. |
- Offerle, Brian, 1967, et al.
(author)
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Surface heating in relation to air temperature, wind and turbulence in an urban street canyon
- 2007
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In: Boundary-Layer Meteorology. - : Springer Science and Business Media LLC. - 0006-8314 .- 1573-1472. ; 122:2, s. 273-292
-
Journal article (peer-reviewed)abstract
- Wind and temperature measurements from within and above a deep urban canyon (height/width = 2.1) were used to examine the thermal structure of air within the canyon, exchange of heat with the overlying atmosphere, and the possible impacts of surface heating on within-canyon air flow. Measurements were made over a range of seasons and primarily analysed for sunny days. This allowed the study of temperature differences between opposing canyon walls and between wall and air of more than 15 degrees C in summer. The wall temperature patterns follow those of incoming solar radiation loading with a secondary daytime effect from the longwave exchange between the walls. In winter, the canyon walls receive little direct solar radiation, and temperature differences are largely due to anthropogenic heating of the building interiors. Cool air from aloft and heated air from canyon walls is shown to circulate within the canyon under cross-canyon flow. Roofs and some portions of walls heat up rapidly on clear days and have a large influence on heat fluxes and the temperature field. The magnitude and direction of the measured turbulent heat flux also depend strongly on the direction of flow relative to surface heating. However, these spatial differences are smoothed by the shear layer at the canyon top. Buoyancy effects from the heated walls were not seen to have as large an impact on the measured flow field as has been shown in numerical experiments. At night canyon walls are shown to be the source of positive sensible heat fluxes. The measurements show that materials and their location, as well as geometry, play a role in regulating the heat exchange between the urban surface and atmosphere.
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| 34. |
- Olvmo, Mats, 1956, et al.
(author)
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Sub-arctic palsa degradation and the role of climatic drivers in the largest coherent palsa mire complex in Sweden (Vissatvuopmi), 1955-2016
- 2020
-
In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
-
Journal article (peer-reviewed)abstract
- Substantial palsa degradation has occurred in Fennoscandia, which is considered to be driven by global climate change. Deeper understanding of the role of different climatic drivers on palsa decay, however, is lacking. We use meteorological data and aerial photographs from 1955 to 2016 to statistically identify the most important climatic drivers affecting changes in lateral-temporal palsa decay rates in the largest coherent palsa complex in Sweden, Vissatvuopmi. We show that wetter, warmer and shorter winters are the main causes of large and rapid changes in lateral-palsa extent since the mid-1950s. By analyzing meteorological data from the 1880s to present, we show that average annual temperature conditions have been unfavourable for palsas for more than a century and average annual precipitation conditions have been unfavourable since the 1940s. The decay rates have likely been amplified over the past 50-60 years, and in particular over the most recent decades, due to the combined effect of adverse air temperature and precipitation conditions. Palsa loss is expected to continue, most likely at a higher rate than today, with serious ecological impacts as a consequence.
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| 35. |
- Olvmo, Mats, 1956, et al.
(author)
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Vissátvuopmi palsmyr – en naturtyp på väg att försvinna
- 2020
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In: Geologiskt Forum. - 1104-4721. ; 108, s. 4-11
-
Journal article (other academic/artistic)abstract
- Det förändrade klimatet i Norden får konskevenser för naturen på många sätt. En naturtyp som påverkas är palsmyrarna som finns i nordligaste Sverige i områden där permafrost förekommer. En detaljerad studie av dessa palsmyrar visar att de inom en ganska snar framtid kan komma att försvinna.
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| 36. |
- Onomura, Shiho, 1985, et al.
(author)
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An intra-urban nocturnal cooling rate model
- 2015
-
In: ICUC9 – 9 th International Conference on Urban Climate jointly with 12th Symposium on the Urban Environment. 20-24 July 2015, Toulouse, France.
-
Conference paper (other academic/artistic)abstract
- Nocturnal urban heat island (UHI) and intra-urban heat island (IUHI) mainly develop through differences in cooling rates. The cooling process consists of two distinctive phases. In the first phase, around sunset, dense urban areas cool more slowly than more open sites, creating large intra-urban temperature differences that are preserved during the whole night. The intensity of this differential cooling is mainly determined by surface characteristics (geometry and material), prevailing weather conditions and season. On the other hand, the cooling during the rest of night, in the second phase, is independent of the surface characteristics. In this study, we investigated how intra-urban cooling rates in the two phases are statistically related to prevailing weather conditions, season, and sky view factor using observation data from Gothenburg, Sweden. Based on the results, a simple statistical intra-urban nocturnal cooling rate model was developed. The model requires only commonly-used meteorological variables and sky view factor. It was shown that the most intensive cooling rate at an open site, in the first phase, was chiefly dominated by the clearness of the sky and wind speed, i.e. the weather conditions. The cooling rate also had a linear relationship with maximum daily air temperature, which can be treated as the seasonal effect. Under clear sky condition, the magnitude of the cooling rate significantly decreased with lower sky view factor, but, under cloudy conditions, the cooling rate varied less or little. In the second phase, cooling rate seemed to linearly decrease as the night progressed and the slope of the decrease was determined by the clearness of the sky. The model was evaluated using three additional datasets, one from Gothenburg, one from London, UK and one from Ouagadougou, Burkina Faso. Gothenburg and London are classified to have a marine temperate climate (Cfb) and Ouagadougou has a tropical steppe climate (BSh) according to Köppen climate classification. The model simulated cooling rates along a smooth profile statistically determined, while observed cooling rates often fluctuated through night. Nevertheless, the model estimated well the total amount of cooling during the whole night. This resulted in the well-simulated nocturnal air temperature. Modeled cooling rates were deviated from the observation at the sites where the large effects of anthropogenic heat and evapotranspiration were present. The effects were not included in this model yet but were found to be significant. This model can be used for multiple applications such as nocturnal human thermal comfort estimation and climate-sensitive urban planning and design.
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| 37. |
- Onomura, Shiho, 1985, et al.
(author)
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Intra-urban nocturnal cooling rates: development and evaluation of the NOCRA model
- 2016
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In: Meteorological Applications. - : Wiley. - 1469-8080 .- 1350-4827. ; 23:3, s. 339-352
-
Journal article (peer-reviewed)abstract
- A nocturnal cooling rate model (NOCRAM) to simulate nocturnal air temperature at urban sites is presented. The model is designed for urban planners, practitioners and researchers who demand meteorological information for urban planning and research applications. The model is based on the concept of nocturnal cooling, progressing in two distinct phases, i.e. site-dependent cooling around sunset and site-independent cooling from about 1 or 2 h after sunset until sunrise. Cooling rates are usually determined predominantly by prevailing weather conditions (i.e. clearness of the sky and wind speed), followed by maximum daily air temperature and by sky view factors. Second phase cooling is chiefly determined by sky clearness and wind speed. The findings and statistical results from the analysis of observational data during warm months (May–September) from Gothenburg, Sweden, as well as from past studies, were used. The model requires standard meteorological variables (i.e. wind speed, incoming short-wave radiation, air temperature, relative air humidity, air pressure) at a reference station as well as geometrical information (i.e. the sky view factor of the site and the geographical co-ordinates of the reference meteorological station). The model simulates the characteristic development of cooling rates in the two phases at open sites and built-up sites with different sky view factors under a wide range of weather conditions in warm months. Using the modelled cooling rates, nocturnal air temperature is estimated easily with the accuracy of root mean square error (RMSE) ≤1.54°C and R2 ≥0.78.
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| 38. |
- Onomura, Shiho, 1985, et al.
(author)
-
Meteorological forcing data for urban outdoor thermal comfort models from a coupled convective boundary layer and surface energy balance scheme
- 2015
-
In: Urban Climate. - : Elsevier BV. - 2212-0955. ; 11, s. 1-23
-
Journal article (peer-reviewed)abstract
- Site-specific meteorological forcing appropriate for applications such as urban outdoor thermal comfort simulations can be obtained using a newly coupled scheme that combines a simple slab convective boundary layer (CBL) model and urban land surface model (ULSM) (here two ULSMs are considered). The former simulates daytime CBL height, air temperature and humidity, and the latter estimates urban surface energy and water balance fluxes accounting for changes in land surface cover. The coupled models are tested at a suburban site and two rural sites, one irrigated and one unirrigated grass, in Sacramento, U.S.A. All the variables modelled compare well to measurements (e.g. coefficient of determination = 0.97 and root mean square error = 1.5 °C for air temperature). The current version is applicable to daytime conditions and needs initial state conditions for the CBL model in the appropriate range to obtain the required performance. The coupled model allows routine observations from distant sites (e.g. rural, airport) to be used to predict air temperature and relative humidity in an urban area of interest. This simple model, which can be rapidly applied, could provide urban data for applications such as air quality forecasting and building energy modelling, in addition to outdoor thermal comfort.
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| 39. |
- 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
-
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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| 40. |
- Reese, Heather, 1964, et al.
(author)
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Multi-scale remote sensing observations of a palsa in degradation phase
- 2021
-
In: EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14455, 2021. - : Copernicus GmbH.
-
Conference paper (other academic/artistic)abstract
- <p>The Viss&#225;tvuopmi palsa complex (N 68&#176;74&#8242;50&#8242;&#8242;, E 21&#176;11&#8242;30&#8221;) is the largest coherent palsa complex in Sweden (ca 274 ha). Aerial photo-interpretation over an area covered by plateau palsas showed a 30% decline in lateral area -- from ca 70 to 49 ha -- that occurred between 1955 to 2016 (Olvmo et al., 2020). Within Viss&#225;tvuopmi, we have more closely studied two single palsas, one dome-shaped and one ridge-shaped, for changes in extent, height and vegetation composition. Manual interpretation of aerial photography between 1955 and 2016 show lateral degradation of 35% and 54% for the dome and ridge palsas, respectively. Since 2018 we have monitored the palsas using images from drones as well as analysis of Planet Dove and Sentinel-2 satellite imagery. Photogrammetry is used to produce orthophotos as well as digital surface models (DSMs) from the drone images, and compared to earlier LiDAR and aerial photo DSMs, to study lateral and vertical degradation.</p><p>The drone-generated DSMs from 2018, 2019 and 2020 show further lateral degradation of the two large palsas. In 2020 a rapid change in vegetation composition was seen on the dome-shaped palsa, where a 250 m<sup>2</sup> area of <em>Betula nana</em> and <em>Empetrum hermaphroditum</em> transitioned to lichen. This vegetation change could be seen in spectral data from both drone and satellite platforms. The future development of this palsa, monitored annually using both fine and medium spatial resolution data, will give insight into the timing and signs of the individual palsas in stages of degradation.</p>
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| 41. |
- Rosell, Staffan, 1966, et al.
(author)
-
Cultivated land – a scarce commodity in a densely populated rural area in South Wollo, Ethiopia
- 2017
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In: Journal of Land Use Science. - 1747-423X .- 1747-4248. ; 12:4, s. 252-270
-
Journal article (peer-reviewed)abstract
- Cultivated and settlement areas were studied in a small area (14km2) in South Wollo, Ethiopia, by aerial photos, satellite images, field observations and interviews. Areas for cultivation/rural settlement decreased a few per cent between 1958 and 2013. Cultivated land per household slowly decreased in 1958–2003 but in 2003–2013 the annual decrease was 3–4 times higher. New farm buildings are often built on cultivated land, and abandoned buildings areas return to cultivation. Rainwater harvesting ponds have increased the areas with perennial crops that are important as a source of income. Tin roofed buildings are signs of improved livelihood. Very small farm size and rain-dependent agriculture combined with climate variability make food security vulnerable. Land-use inventories including remote sensing and local knowledge would be a valuable approach to assess livelihood needs. Further, it should involve decision makers at different levels, but local agricultural extension officers may play a central role
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| 42. |
- Rosell, Staffan, et al.
(author)
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Erratic rainfall and its consequences for the cultivation of teff in two adjacent areas in South Wollo, Ethiopia
- 2015
-
In: Norsk Geografisk Tidsskrift. - : Taylor & Francis. - 0029-1951 .- 1502-5292. ; 69:1, s. 38-46
-
Journal article (peer-reviewed)abstract
- The authors analysed rainfall variability at Combolcha and Hayk in Ethiopia during the short rainy season, the Belg (February–May), in the period 1964–1996 and compared the results with similar data for the period 1997–2012. These towns are located 30 km apart in South Wollo. They have similar in topography and surrounding land use but differ in the amount of rainfall they receive. Daily rainfall data from local weather stations were used as input in a rainfall model for the cultivation of teff to analyse the number of years when it a harvest was possible. After 1996, Belg rainfall declined by 25–30% at both sites. The decline was greatest in February; Combolcha received one-third of its earlier rainfall. The teff model showed that the sowing date changed from February to March in both study areas. Between 1964 and 1996, lack of rain reduced the years with a harvest to every second year in Hayk and every third year in Combolcha. In the period 1997–2012, the number of years with a harvest was slightly reduced in Hayk, whereas in Combolcha it declined to one in every five years. Thus, both sites suffered from the diminished Belg rainfall but the consequences were worse for Combolcha.
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| 43. |
- Rosell, Staffan, 1966, et al.
(author)
-
Rainfall change and its implications for Belg harvest in South Wollo, Ethiopia
- 2007
-
In: Geografiska Annaler, Series A: Physical Geography. - : Taylor & Francis. - 1468-0459 .- 0435-3676. ; 89:4, s. 287-299
-
Journal article (peer-reviewed)abstract
- Most farmers in the Ethiopian highlands depend on rain-fed agriculture. Some areas have the favourable situation of having two rainy seasons, Belg (February-May) and the long rainy season Kiremt (June-October), which is the case in some parts of South Wollo. Tef (Eragrostis tef) is the staple crop that farmers prefer to grow and the 90-day variety is suitable for growing during the short rainy season. One out of eight Ethiopians lives in tef potential areas which have Belg rainfall. The aim in this study is to analyse rainfall variation in South Wollo, in particular the area east of the small town of Hayk, and to study its effect on the ability to grow tef during the Belg season. Results from interviews showed that a more difficult farming situation had emerged during the past 40 years, largely due to deterioration of physical resources such as rainfall. Rainfall is analysed by comparing daily rainfall data from four stations in two periods, 1963 to 1982 and 1984 to 2003, for changes in totals, seasonal distribution and variability. Coefficient of variance, rainy days, rainfall intensity and dry spells were analysed. Results from this study show that there have been minor rainfall changes but greater rainfall variability. During fieldwork key informants were asked if they were able to harvest tef during the past nine years, a period that has been used in a model of rainfall influence on tef cultivation during the Belg season. In both 20–year periods, farmers were able to grow tef every second year. In spite of a greater variability in rainfall the farmers proved their knowledge and flexibility and were able to harvest tef in the same number of years during both periods.
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| 44. |
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| 45. |
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| 46. |
- Thorsson, Sofia, 1972, et al.
(author)
-
Carbon monoxide concentrations in outdoor wood-fired kitchens in Ouagadougou, Burkina Faso-implications for women's and children's health
- 2014
-
In: Environmental Monitoring & Assessment. - : Springer Science and Business Media LLC. - 0167-6369 .- 1573-2959. ; 186:7, s. 4479-4492
-
Journal article (peer-reviewed)abstract
- A majority of households in developing countries rely on biomass fuel for cooking, typically burned in open fires or simple stoves. The incomplete combustion of these fuels causes adverse health effects such as respiratory diseases, especially among women and children. However, quantitative data on pollution levels and on associated diseases are limited. We examined cooking habits and self-reported health in 31 households with outdoor open wood fires in Ouagadougou, Burkina Faso, using structured interviews. In eight households, carbon monoxide (CO) was measured using passive sampling. In addition, meteorology and ambient CO concentrations were assessed. The average CO concentration during cooking was 4.3 ppm, with a maximum of 65.3 ppm and minimum of 0.3 ppm (1-min values). A clear daily pattern was observed, with relatively low concentrations during the day and high during the evening, occasionally exceeding the World Health Organization 1- and 8-h guidelines when the air stabilised. On average, CO concentrations were 43 % higher in kitchens located in closed yards than in those located in open yards, showing that fireplace location affected the levels. Eye irritation and coughing among women and children were reported by 30 % of the households. Based on previously reported relations between CO concentrations and fine particles (< 2.5 mu m), the exposure to biomass smoke appears to be high enough to pose a considerable health risk among women and children in households with outdoor open wood fires. The results suggest that burning should be limited between sunset and dawn and in areas with limited ventilation to reduce pollutions levels.
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| 47. |
- Thorsson, Sofia, 1972, et al.
(author)
-
Different methods for estimating the mean radiant temperature in an outdoor setting
- 2007
-
In: International Journal of Climatology. - : Wiley. - 0899-8418 .- 1097-0088. ; 27:14, s. 1983-1993
-
Journal article (peer-reviewed)abstract
- The mean radiant temperature (Tmrt) is one of the most important meteorological parameters governing human energy balance. In this paper, three different methods of obtaining the Tmrt in an outdoor urban setting are compared. Method A is based on integral radiation measurements and angular factors, method B is based on measurements with a 38-mm flat grey globe thermometer and in method C makes use of the Rayman 1.2 software is used. Measurements were performed in a large open square in a high latitude city - Göteborg, Sweden - during clear to overcast weather conditions in October 2005 and in July and August 2006. Results show that the difference between Method A and Method B was generally relatively small. Most of the discrepancy, caused by rapid changes in radiation, temperature and wind speed was smoothed out using 5 min mean values. By systematically and empirically changing the mean convection coefficient, the accuracy of Method B was improved and a new equation expressing the Tmrt was obtained. With this new equation the 38 mm flat grey globe thermometer could successfully be used to estimate the Tmrt in an outdoor urban setting provided that the wind speed and the air and globe temperatures are measured accurately. The study also shows that the flat grey colour of the globe thermometer slightly underestimates the level of short-wave radiation (i.e. sunshine). Method C works very well during the middle of the day in July, i.e. at high sun elevations. However, the model considerably underestimates the Tmrt in the morning and evening in July and during the whole day in October, i.e. at low sun elevations. In outdoor urban settings where thermal comfort researchers or urban planners and designers require an easy and reliable method of estimating mean radiant temperature, the 38 mm flat grey globe thermometer provides a good and cheap solution.
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| 48. |
- Thorsson, Sofia, 1972, et al.
(author)
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Is Physiological Equivalent Temperature (PET) a superior screening tool for heat stress risk than Wet-Bulb Globe Temperature (WBGT) index? : Eight years of data from the Gothenburg half marathon
- 2021
-
In: British Journal of Sports Medicine. - : BMJ Publishing Group Ltd. - 0306-3674 .- 1473-0480. ; 55:15, s. 825-830
-
Journal article (peer-reviewed)abstract
- Background: The Wet-Bulb Globe Temperature (WBGT) index is a common tool to screen for heat stress for sporting events. However, the index has a number of limitations. Rational indices, such as the physiological equivalent temperature (PET) and Universal Thermal Climate Index (UTCI), are potential alternatives. Aim: To identify the thermal index that best predicts ambulance-required assistances and collapses during a city half marathon. Methods: Eight years (2010-2017) of meteorological and ambulance transport data, including medical records, from Gothenburg's half-marathon were used to analyse associations between WBGT, PET and UTCI and the rates of ambulance-required assistances and collapses. All associations were evaluated by Monte-Carlo simulations and leave-one-out-cross-validation. Results: The PET index showed the strongest correlation with both the rate of ambulance-required assistances (R2=0.72, p=0.008) and collapses (R2=0.71, p=0.008), followed by the UTCI (R2=0.64, p=0.017; R2=0.64, p=0.017) whereas the WBGT index showed substantially poorer correlations (R2=0.56, p=0.031; R2=0.56, p=0.033). PET stages of stress, match the rates of collapses better that the WBGT flag colour warning. Compared with the PET, the WBGT underestimates heat stress, especially at high radiant heat load. The rate of collapses increases with increasing heat stress; large increase from the day before the race seems to have an impact of the rate of collapses. Conclusion: We contend that the PET is a better predictor of collapses during a half marathon than the WBGT. We call for further investigation of PET as a screening tool alongside WBGT.
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| 49. |
- Thorsson, Sofia, 1972, et al.
(author)
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Mean radiant temperature - A predictor of heat related mortality
- 2014
-
In: Urban Climate. - Amsterdam : Elsevier BV. - 2212-0955. ; 10:Part 2, s. 332-345
-
Journal article (peer-reviewed)abstract
- Health studies have repeatedly used air temperature (Ta ), sometimes adjusted for humidity, when analyzing the impact of weather on mortality. The aim of this study is to highlight the importance of mean radiant temperature (Tmrt ) and its impact on heat related mortality. Tmrt is an essential meteorological parameter that influences the thermal comfort (heat load) of humans. It is useful when assessing the impact of weather, especially heat, on people's health. Tmrt is directly influenced by urban geometry and surface material, which also makes it a good measure to identify urban hot spots. The performance of models using Ta and Tmrt for daily mortality is compared for Stockholm County, Sweden. It is demonstrated that Tmrt models fit heat related mortality better than Ta models, which implies that health studies should consider using Tmrt rather than Ta . The use of Tmrt models allows us to determine more accurate thresholds for increased risks of heat related mortality, and thus to better identify adverse weather conditions and heat prone urban geometries. Such information is needed to implement heat-warning systems and mitigate harmful effects of heat stress. © 2014 Elsevier Ltd. All rights reserved.
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| 50. |
- Thorsson, Sofia, 1972, et al.
(author)
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Potential changes in outdoor thermal comfort conditions in Gothenburg, Sweden due to climate change: the influence of urban geometry
- 2011
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In: International Journal of Climatology. - : Wiley. - 1097-0088 .- 0899-8418. ; 31:2, s. 324-335
-
Journal article (peer-reviewed)abstract
- Quantitative information about outdoor thermal comfort, on various temporal and spatial scales, is required to design better cities and mitigate heat problems not only in warm but also in temperate climates. The overall objective of this study is to explore the augmentation of global/regional climate changes by urban features such as geometry in a compact mid-rise high-latitude city (Gothenburg). The magnitude of spatial and temporal variations of intra-urban mean radiant temperatures (Tmrt) is quantified using the SOLWEIG (SOlar and LongWave Environmental Irradiance Geometry) model. Hourly time resolution, statistically downscaled meteorological data, based on the ECHAM5-GCM under the A1B emission scenario is used to simulate changes in Tmrt and physiologically equivalent temperature (PET) at the 2080–2099 time horizon. Results show that urban geometry causes large intra-urban differences in Tmrt, on hourly, daytime and yearly time scales. In general, open areas are warmer than adjacent narrow street canyons in summer, but cooler in winter. According to the ECHAM5-based scenario, the daytime Tmrt will increase by 3.2 °C by the end of this century. This is 0.4° more than simulated increase in air temperature (2.8 °C) and is mainly a result of decreases in summer cloudiness. Occasions of strong/extreme heat stress are expected to triple. This equates to 20–100 h a year, depending on geometry. Conversely, the number of hours with strong/extreme cold stress decreases by 400–450 h. Furthermore, the number of hours with no thermal stress increases by 40–200 h a year. The study confirms the potential for using geometry to mitigate daytime thermal stress. A densely built structure mitigates extreme swings in Tmrt and PET, improving outdoor comfort conditions both in summer and in winter. Furthermore, it highlights the importance of including information on either Tmrt or thermal comfort in climate scenarios to describe the combined effects of changes in multiple climate variables and to more realistically measure the impact on humans.
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