Circulation conditions of strong and elemental wind over southwestern Ukraine

Abstract

Introduction. Nowadays the problem of storm winds appears to be a very relevant one in those spheres of human activities related to safety of human living, coastal infrastructure, seafaring, aviation etc. One of the conditions for successful forecasting of strong winds is familiarization with wind characteristics of the study area and with synoptic conditions causing them. The below listed results of research form continuation of previous works for search of a better synoptic classification reflecting completeness of macroscale baric processes causing formation of winds, including strong winds, over the South of Ukraine and also providing an opportunity to forecast winds in a more accurate manner.
 The purpose of this publication consists in analysis of interaction of large-scale atmospheric circulation with formation of unfavorable weather conditions (strong and very strong winds) on the north-west coast of the Black Sea.
 Methods and results. The impact of storm winds is significant for functioning of the national economic complex of the North-Western Black Sea region. In order to investigate this effect there were fifty seven cases of wind amplification up to criterion of strong ≥ 15 m·s-1 and very strong ≥ 25 m·s-1 selected within the Odessa region during the period from October to March in 2011 – 2014.
 Indexes of Katz circulation for isobaric surface of 500 hPa were calculated as per the data of synoptic archive for the cases with wind speed of ≥ 15 m·s-1. A more detailed study of the structure of macrocirculation processes under strong winds, except for Katz indexes, is provided by means of classification and calendar of successive change of elementary circulation mechanisms (ECM) in the Northern hemisphere according to Dzerdzeyevskyi B.L. and typification of synoptic processes developed at the Department of Theoretical Meteorology and Meteorological Forecasts of OSENU. It was determined that strong and very strong winds often occur in southern and central regions, particularly at the stations located on the shores of seas and estuaries (Bilgorod-Dnistrovskyi, Ust-Dunaysk, Pivdennyi port). Meridional type of atmospheric circulation (77.2%) creates favourable conditions for wind amplification in the North-Western part of the Black Sea up to the criterion of strong and very strong one, zonal type of circulation constitutes 22.8% from the total number of cases. Meridional type of circulation is mainly represented by mixed and western forms – (24.6%) and (22.8%) respectively. Main types of synoptic situations (5, 6) of Katz typification that used to cause strong winds were revealed. Most frequently strong wind was observed while moving of cyclonic vortexes from the South (ECM type – 12a, 13z) and in the area of cyclones and anticyclones interaction.
 Conclusion. It was found that wind speed amplification in the South of Ukraine up to the criteria of strong and very strong one mainly occurs due to the meridional type of atmospheric circulation which is dominated by mixed or western forms of circulation as per Katz typification, ECM type 12a and 13z according to Dzerdzeyevskyi B.L. and types 5 (subtype 5.2) and 6 (all subtypes depending on ECM) as per synoptic typification of OSENU.
 Directions for further research should include the following. The conclusions have preliminary character and need confirmation on the basis of bigger scope of statistical data.