Circulation conditions of winter time heavy precipitation formation in Transcarpathia

Abstract

Over the recent decades the research efforts associated with the atmosphere intensified due to the increasing urgency of the problem of global climate change and the impact of anthropogenic factors thereon. Atmospheric moisture, its phase state and moisture exchange play a significant role in the formation of weather and climate. The article analyzes modern circulation conditions over the territory of Transcarpathia in winter over the period from 2007 to 2016 when strong and very strong precipitation was formed. Using the typification of weather processes over a given region and taking into account the elementary circulation mechanisms (the EСMs) proposed by B. L. Dzerdzeevskyi, V. M. Kurgan and Z. M. Vitvytska the most probable atmospheric processes and types of synoptic situations that create conditions for extreme precipitation in the Transcarpathian region were identified. According to observation data from 9 hydrometeorological stations, 30 hydrological stations and 15 automated hydrometeorological stations extreme precipitation series for three winter months were obtained. The following objective analysis data of the US National Center for Atmospheric Prediction (NCEP) and National Center for Atmospheric Research (NCEP/NCAR) were used for calculating the blocking indicators: geopotential fields at the level of 500 hPa. According to the research period, precipitation of ≥ 20 mm / 12 h were more often recorded in December (47 %), and year-wise – in 2011, that is, unevenly over time. Precipitation of 30 mm / 12 h (37 cases from 66 - 56,1 %) formed only as a result of type 6 synoptic processes – cyclonic circulations with great atmospheric pressure gradients. Strong precipitation in Transcarpathia is much more often associated (75,7 %) with ECM 11 and ECM 12 types. The highest repeatability of hazardous precipitation is observed in December and associated possibly with blocking anticyclones. As an example, the article describes the situation over the period from 22 to 26 December, 2009 when the maximum amount of precipitation per day was recorded: 82 mm at the Ust-Chorna and Rusʹka Mokra meteorological stations, December 26, 2009. Azor and Arctic blockings may contribute to stationing of the blocked southwest and northwest cyclones and formation of intense and long-term precipitation and other extreme weather phenomena over the orographically inhomogeneous territory of Transcarpathia.

Keywords

• strong precipitation, intensity, typification, weather processes, elementary circulation mechanism