Atmospheric circulation conditions during winter warm spells in Central Europe

Abstract

The objective of the paper was to characterise the temporal and spatial variability of winter warm spells in Central Europe in the years 1966/1967-2015/2016 and to determine the circulation conditions of their occurrence. The applied data were obtained from the Polish Institute of Meteorology and Water Management, Deutscher Wetterdienst and the National Centre for Environmental Prediction/National Centre for Atmospheric Research. A warm spell was defined as a sequence of at least three warm days, i.e. when the maximum air temperature is higher than the 95th percentile of the probability density function designated from observation. The research has proven that over the study period the air temperature increased in the winter season in Central Europe and this translated into an increase in the number of warm days. An average of 3-5 warm spells was recorded per 10 years. The most numerous warm spells occurred during three winter seasons, i.e. 1989/1990, 2006/2007 and 2015/2016. The occurrence of warm spells was related to positive anomalies of geopotential heights over the study area in the cross section of the entire troposphere. Maximum anomalies appeared at 250 hPa geopotential height, and they developed on average 9 days before the commencement of warm spells over the study area.

Seasonal Variability of Trends in Regional Hot and Warm Temperature Extremes in Europe

“…Existing studies in Central Europe and Eastern Europe focus primarily on hot extremes in summer and remain in agreement that these extremes have been rapidly increasing in terms of frequency, intensity, and spatial range since the mid-20th century [47][48][49][53][54][55]. Considerable changes also occur in these two regions in winter [66]. Our results indicate that changes in winter manifest themselves particularly strongly in terms of a large increase in TXx as well as a substantially higher frequency of occurrence of very severe ETEs in recent decades.…”

“…Kivinen et al [63] obtained similar results for the Northern Fennoscandia for the period 1914-2013, and determined the occurrence of a much higher number of extremely warm days in April and October over the last 20 years of the study period. Chapman et al [65] examined the Central England Temperature Record and found a two-to threefold increase in the frequency and duration of winter warm spells since the late 1800 s. Significant increasing trends in the number of warm winter days were also noted for Central Europe [66] as well as for high mountain sites in the Swiss Alps [67]. Research results for Southeastern Europe vary.…”

Germination responses to winter warm spells and warming vary widely among woody plants in a temperate forest

“…In the Northern Hemisphere, warm spells during winter have increased in duration and/or frequency, e.g . throughout eastern Canada (Shabbar & Bonsal 2003), in Europe (Tank et al 2002; Tomczyk et al 2019) and in the Swiss Alps (Beniston 2005). Concomitantly, winters are warming and shortening and experiencing reduced snowfall and increased rain with climate change (IPCC 2013).…”

Wintertime cold and warm spells in the eastern part of the Baltic Sea region

“…(2020). The increase in wintertime air temperature in Central Europe has been detected by Tomczyk et al (2019), however most of these changes were statistically insigni cant. In this study, large-scale WSs have been associated with the advection of warm air masses and anomalies in geopotential height in the entire troposphere, with the largest anomalies at 250 hPa several days before the extreme event.…”