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Magazine of Cartography


















UDC 551.515

Shchehlov O.

Winter synoptic processes with extreme negative temperature anomalies in Ukraine

      The article describes the typical synoptic processes that lead to extreme-cold winter temperatures over the past 20 years (1997-2017) in Ukraine. The NCEP/NCAR reanalysis data is used to select extreme temperatures below the 5th percentile of the surface air temperature distribution function for a regular grid of the territory of Ukraine. The classification of pressure fields with extreme-cold temperatures allowed us to identify four main types of synoptic processes. The first type of synoptic processes is the cold air advection associated with the Siberian High. The low pressure at the middle troposphere is the characteristic feature. As a rule, this type of the processes leads to the lowest air temperatures as for Ukrainian climate conditions. The cold air usually expands practically throughout all territory of Ukraine. In this case, the duration of such processes, as a rule, is longer relative to the other cold processes. The processes of the second type characterize the advection of cold air from the north into the territory of Ukraine. At the night time, the temperature of the air can vary within -16...-24 C, which is relatively higher than in the case of Siberian cold air. The third type of synoptic processes describes advection of cold air from the northwest to the territory of Ukraine. The advection of cold air from the northwest is characterized by the highest frequency in the first half of the winter season. The cold air flows are caused by cut-offs and the temperature at night practically throughout the territory of Ukraine may reach -15...-20 C. For the field of surface pressure, a core of high pressure over northwestern Europe is observed. All the types of processes cause extreme cold air temperature over the territory of Ukraine which often is lower than a value of 5-percentile air temperatures. The frequency of each type of process that leads to such extreme temperatures events in Ukraine during the winter season is approximately equal.

      Keywords: synoptic processes, extreme-cold temperatures, temperature anomaly, Ukraine.


      Arrived to editorship: August 31, 2018.


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