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Vliv vegetace na letní teplotní extrémy ve městech hodnocené z pozemních a leteckých dat
ROHÁČ, Václav
This thesis examines the effect of surface types and vegetation types on ambient temperature during summer temperature extremes. The theoretical part targets the topics of remote sensing, electromagnetic radiation, urban and global climate. Within the practical part, 3 areas of interest were selected from aerial hyperspectral data from the territory of the statutory city of České Budějovice, each representing a different part of the city in terms of land use. By means of data analysis, graphs showing the influence of the relative representation of the variant surfaces on the temperature were created using the linear regression method. From the maps of tree species occurring in the parks of the first two areas, the most abundant species were selected and the average temperature within 2 meters of them was examined. The thesis also includes an evaluation of a questionnaire answered by city residents on the topic of preferences and knowledge about the urban green space.
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Heat waves over Central Europe in ALADIN-Climate/CZ regional climate model: evaluation and future projections
Lhotka, Ondřej ; Farda, A. ; Kyselý, Jan
We evaluated a simulation of Central European heat waves and analysed possible changes of their characteristics in the future climate using the ALADIN-Climate/CZ regional climate model with 25km horizontal grid spacing. Lateral boundary conditions were provided by the ARPEGE global climate model, using historical forcing and the SRES A1B scenario. Observed data were taken from the E-OBS gridded data set. Heat waves were evaluated over 1970−1999 and changes in their characteristics were assessed for 2020−2049. Their definition is based on exceedance of the 90th percentile of summer daily maximum temperature calculated separately for modelled and observed data. ALADIN-Climate/CZ simulates characteristics for the recent climate quite well, especially the overall severity of heat waves. In contrast, temperature amplitude was considerably overestimated. This model projects an increase in overall heat wave severity by a factor of 2 to 3 in the future climate, primarily driven by an increasing number of events. The study shows that ALADIN-Climate/CZ is generally capable of simulating Central European heat waves, which gives more credibility to model projections of future heat waves.
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Analysis of temporal variability and spatial characteristics of heat waves in central Europe using extremity index
Lhotka, Ondřej ; Kyselý, Jan
Heat waves have severe consequences on natural environment and society. Th e majority of studies defined heat waves from station data only, so there is a need to examine these events not only from the aspect of point characteristics of air temperature and duration, but also from the view of their spatial extent. In this study, heat waves over Central Europe were analysed using the gridded E-OBS dataset. Th e extremity index of heat waves, which takes into account their spatial extent, duration, and peak temperature, was proposed and used to analyse variability of heat waves over Central Europe from 1950 to present. We delimited 220 hot days and 21 heat waves and computed the extremity index for each heat wave. Th e eight most signifi cant heat waves based on the extremity index were visualized. Temporal variability of hot days and heat waves was analysed and we demonstrate that the number of hot days and the severity of heat waves have been increasing.
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