Occurrence of strong and very strong heat stress in Poland and its circulation conditions

Abstract

Abstract The primary objective of the paper was the determination of the atmospheric circulation favouring the occurrence of strong and very strong stress of the human organism due to heat stress in Poland. The paper was prepared based on data obtained from the Institute of Meteorology and Water Management – National Research Institute and the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR). The criterion of extreme stress of the human organism adopted in the paper covered conditions in which the Universal Thermal Climate Index (UTCI) value was higher than 32 °C. The research showed a statistically significant increase in half of the analysed stations and an increasing tendency or no changes in the remaining stations. Moreover, after 1990, conditions particularly strenuous for the organism were recorded (UTCI > 40 °C) over a major part of the territory of Poland. The occurrence of days with strong and very strong heat stress in Poland was related to the presence of high-pressure systems blocking zonal circulation. The research permitted the designation of three types in which the pressure field showed common features, but differed in the location of anticyclonic systems.