Agnieszka SULIKOWSKA, Department of Ecology, Climatology and Air Protection, University of Agriculture in Krakow, Poland
Agnieszka WYPYCH, Department of Climatology, Jagiellonian University in Krakow, Poland
Zbigniew USTRNUL, Department of Climatology, Jagiellonian University in Krakow, Poland
Springtime cold extremes can affect numerous sectors, including agriculture, human health, tourism, and various ecosystems that are sensitive to cold temperatures. Here we investigate the potential driving physical mechanisms of such events. The aim of the study is to identify distinctive circulation patterns favouring the occurrence of springtime cold extremes in Central Europe regarding their timing in the season. A cold extreme is defined as a day with minimum temperature falling below the local 5th and/or 10th percentile across at least 10% of the study domain area. Cold extremes in spring (March-May) over 1950-2020 are analysed based on the E-OBS v.23.1e gridded dataset (0.1° × 0.1°) with the use of the Extremity Index (Sulikowska and Wypych, 2021) that allows assessing these events in terms of their attributes, i.e. intensity and spatial extent. The connection to circulation patterns is examined via composite maps of 500hPa geopotential height fields from ERA5 reanalysis and additionally with the use of the subjective Grosswetterlagen circulation types catalogue. The study is conducted in several 10-days sub-periods of the season to investigate whether circulation patterns favouring cold extremes change during spring.
The key findings of the study highlight the transitory nature of the spring season indicating a changeable relationship between circulation patterns and temperature during this time of year. At the beginning of a season circulation types triggering cold extremes are related to positive pressure anomalies, thus being analogous to these connected with wintertime cold events. This relationship reverses in late spring when cold extremes are accompanied by negative pressure anomalies, resembling circulation patterns associated with cold weather during summer.
Mots clés : cold extremes|air temperature|atmospheric circulation|Grosswetterlagen|Central Europe
A105304AS