Extreme events in the Czech Republic: Recent development and projection

It is critical for decision makers to be aware of the projections of the extreme weather phenomena in future when preparing policies for adaptation and risk management.

This topic has been addressed by the project “ Prediction, Evaluation and Research for Understanding National sensitivity and impacts of drought and climate change for Czechia“  where we estimated risks of hydrometeorological phenomena and their expected changes during the 21st century.

For the territory of the Czech Republic we identified as the main risks the following phenomena related to the extremes weather: heat wave, cold wave, extreme wind, extreme precipitation (torrential and permanent), drought and the subsequent risks e.g. firerisk, severe thunderstorm and subsequent risks. In our contribution, we focused on assessment of the changes in the occurrence of heat waves and extreme wind.

To quantify changes in occurrence of heat waves the indices related to weather alerts were defined and their changes were evaluated for the period with station observations. The threshold for indices corresponds to the alerts of high level of danger for CZ. These limits were chosen with respect to impact of extreme meteorological phenomena on society and environment. The number of days with maximum temperature above 34,0 °C and days with minimum temperature above 20,0 °C have been evaluated and on top of the number of days with maximum (minimum) temperature above these thresholds we studied the length and intensity of heat waves.

When studying changes in the occurrence of extreme wind speed the threshold for the maximum wind speed 17,2 m/s has been used in accordance with International Meteorological Vocabulary, WMO-No. 182.

We evaluated the changes in frequency of extreme phenomena between the periods 1961–1990 and 1991–2020 and studied the trend. On the basis the regional climate model data we estimated the projection of occurrence of studied extreme phenomena.