Robert Twardosz

Abstract

This study determines the frequency, location and spatial extent of such large-area monthly thermal anomalies,which are referred to in this paper as continental-scale thermal anomalies (CTAs). The research was based on monthly mean air temperature values from 210 weather stations over the 68-year period 1951-2018. A CTAis defined as an anomaly when the monthly mean temperature exceeded the long-term average by at least 2 standard deviations at a minimum of 40 stations. This study attempts to explain the occurrence of such CTAs (negative CTAs- and positive CTAs+) in relation to the circulation conditions over Europe. In the years 1951-2018, there were 16 CTAs- (mainly in winter and autumn) and 25 CTAs+ (predominantly in summer). One manifestation of climate warming is the ever less frequent occurrence of CTAs- and a growing frequencyand spatial extent of CTAs+. The immediate cause behind CTAs was the occurrence of characteristic synoptic situations, leading to intensified advection of cold or hot air masses, often driven by radiation factors. The formation of CTAs- was much more often associated with very extensive and long-lasting anticyclonicsystems, and that the associated synoptic situations over Europe lasted much longer than in the case of CTAs+.

Keywords: contemporary warming, extreme temperatures, warm months, cold months, mean sea level pressure, Europe

Robert Twardosz [r.twardosz@uj.edu.pl], Faculty of Geography and Geology Jagiellonian University Gronostajowa str. 7, 30-387 Kraków: Poland
Zuzanna Bielec-Bąkowska [zuzanna.bielec-bakowska@us.edu.pl], Institute of Earth Sciences, Faculty of Natural Sciences University of Silesia in Katowice Będzińska str. 60, 41-200 Sosnowiec: Poland