The urban near surface atmosphere is of great concern since it affects the climate to which an increasing amount of people are immediately exposed. This study investigated the microclimate in central Stockholm in terms of the thermal conditions in the 0-2.5 m air layer and the water and heat exchange processes at different types of surfaces found within the urban environment. The main objective was to improve our understanding of the urban small-scale climate system. The urban microclimate was measured in terms of vertical air temperature profiles along a horizontal transect running through a vegetated park and its built-up surroundings during three clear and relatively calm summer days. The results showed that the air temperature at 1.2 m height within the park was 0.5 to 1.5 K lower than in the surrounding city blocks, and that the thermal stratification was generally stable (increasing temperature with height) in the park and unstable (decreasing temperature with height) in the built-up areas. In addition, there were a few examples of temperature gradients orientated in different directions within the lowest 2.5 m air layer, indicating horizontal advection between the park and the built-up areas. Climate conditions simulated with a three-dimensional microclimate model agreed well with observations and the model was therefore assumed to provide reasonable representations of important climate processes such as surface-air energy exchange processes. However, there were some discrepancies between observations and simulations that are discussed in terms of differences in real and modelled heat storage processes and wind conditions. Processes that need to be included for a more precise model description of areas such as the Stockholm environment include dynamic heat storage in buildings and dynamic wind forcing during the course of the simulation. A soil-vegetation-atmosphere transfer model was used to study soil water transport, the surface energy balance of an asphalt surface, and the impact of urban climate on evapotranspiration. Based on model calibration to field measurements of soil water content in a till catchment outside Stockholm, new parameter values were estimated that can be used for water flow modelling of till soils. The heat fluxes of an asphalt surface were reliably simulated without knowledge of site-specific calibration and the model was useful in identifying problems with energy balance closure based on measurements only. Simulations of ‘urban’ modifications to the forcing climate conditions demonstrated that increased air temperature, and thereby increased vapour pressure deficit, had most effect on evapotranspiration from tall vegetation, while increased long-wave radiation raised grass evapotranspiration the most. / QC 20100901

This study analyzes the trends in temperature, and their extremes, in the Greater Toronto Area (GTA) in the context of urban heat island. The trends in annual and seasonal temperature changes were investigated in the GTA over the past century and a half with special focus on 1970-2000. The Mann-Kendall test is used to assess the significance of the trends and the Theil-Sen slope estimator is used to identify their magnitude. Statistically significant increasing trends for mean and minimum temperatures are observed mainly at the urban and suburban stations. The sequential Mann-Kendall test is used to identify any abrupt change in the time series of temperature (31 -161 years), and the results indicate that increasing trend for annual mean temperature has started after 1920 at Toronto downtown, after the 1960s at the suburban stations, and has increased significantly during the 1980s at all stations, which is consistent with the pace of urbanization during these periods in the GTA. The observed urban heat island (UHI) in Toronto is quantified and characterized by considering three different rural stations. The UHI intensity (∆Tu-r) in Toronto is categorized as winter dominating or summer dominating depending on the choice of a rural station. The results from the trend analysis of annual and seasonal ∆Tu-r suggest that the choice of the rural station is crucial in the estimation of ∆Tu-r, and thus can overestimate or underestimate its prediction depending on the location and topographical characteristics of a rural station relative to the urban station. The trends in extreme temperature indices are also investigated and the results indicate that indices based on daily maximum temperature are more pronounced at the urban and suburban stations compared to that at the rural stations. The changes in the trends for extreme indices based on daily minimum temperature are consistent at all stations for the period of 1971-2000. With the decrease in the percentage of cold nights and the increase in the percentage of warm nights, the diurnal temperature range has decreased throughout the GTA region. The analysis of heating degree days and cooling degree days revealed that the former is associated with decreasing trends and the latter exhibited increasing trends at almost all stations in the GTA. Finally, it is evident from the results that urban heat island phenomenon exerts warmer influence on the climate in cities, and with the current pace of urbanization in the GTA, it is imperative to understand the potential impact of the emerging UHI on humans and society.

This study analyzes the trends in temperature, and their extremes, in the Greater Toronto Area (GTA) in the context of urban heat island. The trends in annual and seasonal temperature changes were investigated in the GTA over the past century and a half with special focus on 1970-2000. The Mann-Kendall test is used to assess the significance of the trends and the Theil-Sen slope estimator is used to identify their magnitude. Statistically significant increasing trends for mean and minimum temperatures are observed mainly at the urban and suburban stations. The sequential Mann-Kendall test is used to identify any abrupt change in the time series of temperature (31 -161 years), and the results indicate that increasing trend for annual mean temperature has started after 1920 at Toronto downtown, after the 1960s at the suburban stations, and has increased significantly during the 1980s at all stations, which is consistent with the pace of urbanization during these periods in the GTA. The observed urban heat island (UHI) in Toronto is quantified and characterized by considering three different rural stations. The UHI intensity (∆Tu-r) in Toronto is categorized as winter dominating or summer dominating depending on the choice of a rural station. The results from the trend analysis of annual and seasonal ∆Tu-r suggest that the choice of the rural station is crucial in the estimation of ∆Tu-r, and thus can overestimate or underestimate its prediction depending on the location and topographical characteristics of a rural station relative to the urban station. The trends in extreme temperature indices are also investigated and the results indicate that indices based on daily maximum temperature are more pronounced at the urban and suburban stations compared to that at the rural stations. The changes in the trends for extreme indices based on daily minimum temperature are consistent at all stations for the period of 1971-2000. With the decrease in the percentage of cold nights and the increase in the percentage of warm nights, the diurnal temperature range has decreased throughout the GTA region. The analysis of heating degree days and cooling degree days revealed that the former is associated with decreasing trends and the latter exhibited increasing trends at almost all stations in the GTA. Finally, it is evident from the results that urban heat island phenomenon exerts warmer influence on the climate in cities, and with the current pace of urbanization in the GTA, it is imperative to understand the potential impact of the emerging UHI on humans and society.

published_or_final_version / Architecture / Master / Master of Philosophy

published_or_final_version / Geography / Master / Master of Philosophy

No description available.

This thesis aims to examine the spatial relationship between elevated air temperatures and populations most vulnerable to heat across the urban environment. To assess this correlation, the analysis focuses on the cities of Atlanta, Georgia and Minneapolis, Minnesota. A three-part methodology was employed: first, continuous air temperature was estimated using satellite imagery and weather station observations; second, a heat vulnerability index was generated based on demographic, social, and environmental variables at the Census block group level; and third, a spatial statistical analysis was performed to measure the correlation between the hottest temperatures and the populations most vulnerable to heat. Finally, the thesis concludes with policy recommendations that address the comprehensive nature of vulnerability in relation to extreme heat. As municipalities and local governments plan for a future with warmer temperatures and larger urban populations, effective policies must be designed with respect to both the social and physical environments; the results herein can help inform such strategies.

Thesis (Ph. D.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

The primary objectives of this study are to understand if and how cities are adapting to heat and water stress and to characterize their understanding of the potential tradeoffs associated with vegetation-based strategies. I address these objectives using two approaches: a comparative analysis of climate adaptation and sustainability planning documents in cities vulnerable to heat and water stress and an in-depth case study of the response to heat and water threats in Los Angeles. The comparative analysis of city plans builds a broad understanding of how cities are planning to adapt to heat and water stress and the degree to which they articulate an understanding of, and mitigate the potential for, maladaptive measures. The Los Angeles case study provides the opportunity to more deeply trace how the process of adapting to heat and water stress has unfolded in a single city. To do so, I locate the city’s contemporary policies in an historical continuum with previous municipal environmental policy efforts, in local patterns of urban development and their entailing political and economic foundations, and in regional, state, national, and international environmental policy hierarchies.

Urban heat island is a phenomenon of different temperatures in cities compared to temperatures in the surrounding landscape. The intensity of this phenomenon can be influenced by the presence of vegetation in cities. There is evaluated the effect of vegetation on microclimate in various parts of the city České Budějovice in this thesis. The assessment is based on the evaluation of multispectral Landsat satellite images and thermal images, which were taken in-situ using thermal camera, and their statistical processing. The results show statistically significant differences in surface temperatures in the different areas of the city with a different amount of vegetation. Surface temperatures are significantly lower in areas with a large amount of vegetation than in areas without vegetation. Equally, selected vegetation surfaces have lower temperatures compared to anthropogenic surfaces, at least about 9 ° C.