Impact of the North Sea – Caspian Pattern on the formation of regimes of air temperature and precipitation in the Caucasus region

Е.А. Rybak1,2, N.A. Yaitskaya1,2, O.О. Rybak1,2

1 Sochi Research Center of RAS, Sochi, Teatralnaya St., 8a

  E-mail: elena.rybak@gmail.com

2 Branch of Institute of Natural and Technical Systems, Sochi, Kurortny Ave., 99/18

DOI: 10.33075/2220-5861-2018-3-57-64

UDC 551.582

Abstract:

   In this paper, we consider links between characteristics of the regional climate with one of quasi-stable modes of the atmospheric circulation, the North Sea-Caspian Pattern (NCP). The NCP index is calculated as a normalized residual between 500 mb geopotential heights in the centers of action in the North Sea and in the northern part of the Caspian Sea. When the phase of the NCP is positive, the atmospheric circulation in the region has a more pronounced meridional character. In case the phase is negative, the circulation is mostly of the zonal character. During positive phase in winter period, prevailing northern air flows over the greater part of the Eastern Europe, over the Black Sea and over the Caspian Sea, result in substantial temperature decrease with respect to climatic means. During negative phases, the pattern is reverse. Air temperature anomalies are characterized by relatively high spatial correlation because they are formed under the influence of the large-scale atmospheric circulation. At the same time, precipitation regime is highly influenced by the local conditions and therefore has low spatial correlation.

   The purpose of the research is to evaluate possibility of disposal of an expected NCP phase for prediction of surface air temperature and precipitation rate, especially in the mountain regions of the South of Russia and, as well, to use them as input meteorological variables in the mathematical models of mountain glaciers’ dynamics.

   The region of interest covers the southern part of European Russia to the south of the line connecting Rostov and Volgograd including the Black Sea and the Sea of Azov coastal zones. We analyzed records of surface air temperature and precipitation rates from 31 regular meteorological stations in the region under discussion. Original 3-hour data were averaged over winter months (December-January-February), summer months (June-July-August), cold part of the year (from October to March), warm part of the year (from April to September) and over the whole year.

   The research revealed that the temperature regime in the mountain and piedmont areas of the Caucasus in winter season and in the cold part of the year is formed mostly under the influence of anomalous atmospheric circulation associated with the positive or with the negative phase of the NCP. During the summer period impact of the NCP on the temperature regime is small. Precipitation regime depends mostly on the local conditions, especially in summer months, when correlation coefficient does not exceed 0,3. Basing on the research results one can conclude that the NCP is not an appropriate predictor for precipitation. On the contrary, it can be used as a predictor of the air temperature in the cold part of the year. It is expedient to use, for instance, strong linear correlation of the NCP index and air temperature for detailing regional seasonal predictions. Particularly, in the surroundings of Sochi and Krasnaya Polyana the lower 95% confidential interval of correlation coefficient is |R|³0,6. It means that close relationship between the NCP and air temperature can be applied for establishing prognostic estimates of avalanche situation. This possibility is essentially important for planning mountain ski industry not only for resorts in the region of Krasnaya Polyana but also for the whole Central and Western Caucasus.

Keywords: climate, regional climate, air temperature, precipitation amount, climate prediction, Caucasus.

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