Warm and Cold Waves in South-Eastern (V) Bioclimatic Region in Years 1981–2010

Abstract

Lublin and Roztocze regions are placed in bioclimatic division (by T. Kozłowska-Szczęsna) in 5th south-eastern region. This area can be characterized by a high number of days with high air temperature (Kozłowska-Szczęsna et al., 1997) and by highest number of frost days in Poland (Błażejczyk, Kunert 2011). In this region, there is high frequency of cold spells; an occurrence, which can last over 15 days (Kuchcik et al., 2013).
In this paper, warm and cold waves are calculated by method elaborated by Wibig (2007), where waves are determined by maximum air temperature (warm and cold days) and minimum air temperature (warm and cold nights) based on standard deviation from the average, expressed in standard deviation. Days, where air temperature was higher than average by more than 1.28 standard deviation was regarded as very warm, and those with lower air temperature than average by more than 1.28 standard deviation was regarded as very cold (Wibig 2007).
For the purpose of this research, data from stations Lublin-Radawiec, Zamość and Tomaszów Lubelski were used, for the 1981–2010 period. During that time, short (3–5 days) waves of warm days occurred slightly more often than for waves of cold days, but in case of long waves (11–20 days) cold waves dominated, which is very characteristic for south-eastern (V) bioclimatic region. The waves of cold days were particularly long at Tomaszów Lubelski and Zamość stations. The average number of short (3–5 days) cold waves (night) on examined stations of south-eastern bioclimatic region was 3–4 waves per year and this was more than average number of short warm waves (night), which fluctuated between 2 to 3 waves per year (inversely to the case of waves of warm days). In the first decade of 21st century, the decrease in number of cold days is visible, but number of warm nights has increased during that time.