The anomalously cold January 2017 in the south‐eastern Europe in a warming climate

• Published in: International Journal of Climatology
• Main Author: Demirtaş, Meral
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2022
• Subjects: North East Atlantic
• Online Access: http://dx.doi.org/10.1002/joc.7574; https://onlinelibrary.wiley.com/doi/pdf/10.1002/joc.7574; https://onlinelibrary.wiley.com/doi/full-xml/10.1002/joc.7574; https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/joc.7574

Abstract The January 2017 wintry weather spread over the south‐eastern Europe and Turkey ‐which led to extremely low temperatures (−40°C) and snowstorms. This study strived to draw together key prominent dynamical mechanisms governing seasonal temperature variability in a warming climate, which can serve as a recognizable flow pattern and yield insights into their most important triggering mechanisms and maintenance. The connection between cold spells and atmospheric blocking was elucidated by utilizing an objective cold‐wave indicator and a two‐dimensional blocking indicator. The cold‐wave indicator ‐which uses a non‐parametric approach to diagnose a spatiotemporally varying minimum temperature threshold‐ gave an objective account of cold spells of January 2017. An analysis of cold‐wave activities indicated that parts of Europe and Turkey went through very cold weather conditions for approximately 7–12 days. Cold spells were closely related to the position of the blocking and the 500 hPa geopotential height anomalies. The horizontal distribution of surface temperature anomalies indicated that associated temperature anomalies were quite large in the south‐eastern Europe and Turkey. The persistence of the anticyclone over the eastern Atlantic steered the low pressure system towards the south‐eastern Europe and Turkey. The collocation of prominent atmospheric patterns led to the formation of extreme cold spells. Our results of two‐dimensional atmospheric blocking index revealed that blocking lasted for 5 days over the eastern Atlantic ‐which enabled anticyclonic conditions persisting. Diagnostics indicate that the imposed blocking over the north‐east Atlantic alters the direction and strength of the zonal flow in the south‐eastern Europe, which influences the behaviour of synoptic‐scale flow in its downstream. These results are consistent with the inferences drawn from surface temperature analyses, which accentuate the role of blocking imposed circulation on the anomalous low temperature anomalies. Characteristics ...