Abstrakt
Our research focuses on analysis of extreme maximum air temperature events (EXHTEs) in the Czech Republic in the period 1961-2010, their climatological characteristics and on the identification of synoptic-scale circulation conditions conductive to them. EXHTEs are detected using the Weather Extremity Index (WEI) combining return periods of daily maximum air temperature, duration of events and the extent of the affected area.
We selected 37 EXHTEs as non-overlapping periods with the highest WEI. Some long EXHTEs were divided into several shorter synoptically homogeneous episodes.
Using two-level divisive clustering of 700 hPa air temperature and wind field anomalies we obtained 4 main variants of synoptic-scale circulation conditions. The most frequent variant associated with extreme episodes is characterized by a westerly flow connected with a high pressure ridge extending from the south-west over central Europe or with an anticyclone centred to the south.
The most extreme episodes occurred during the variant characterized by an easterly flow between a high pressure area to the north-east and a low pressure area to the southeast.