Abstract
Cyclonic activity in the midlatitudes is a form of general atmospheric circulation, and the most intense cyclones are the cause of hydrometeorological anomalies that lead to economic damage, casualties and human losses. This paper examines the features of variability of intense cyclonic activity in the Black Sea region and the examples of their regional manifestations in the storm types. Based on 6-hourly NCEP/NCAR reanalysis data on 1000 hPa geopotential height fields with 2° × 2° spatial resolution and using the methodology by M.Yu. Bardin, objective data were obtained for the identification and estimation of the frequency of deep cyclones (reaching 0.75 and 0.95 quantiles by intensity and depth—intense and extreme cyclones, respectively) for the Black Sea region during the period 1951–2017. Additionally, a specific methodology of more precise cyclone identification based on spherical spline interpolation was successfully applied, and then the two methodologies were compared. The key point of the study is the following: In the background of negative significant linear trends and interdecadal variability (period of about 35 years), typical scales of their interannual variability on the periods of about 2.5–3.5 and 6–8 years were identified. These periods coincide with the time scales of the North Atlantic Oscillation and El Nino–Southern Oscillation, providing an outlook for further study of the patterns of their connection. Besides, seasonal forecasts of frequency of intense cyclones in the Black Sea region were successfully modeled using an artificial neural network technique. Finally, the case studies of regional manifestations of deep cyclones in the types of storms in the northern Black Sea coast revealed substantial differences in the location of deep centers of cyclones and storm tracks associated with the large-scale pressure fields.
Highlights
Knowledge of the periods and patterns of regional climate variability is important for the development of long-term forecasts of weather and climate anomalies and for solving applied problems of long-term planning of regional sustainable development under climate change [1,2,3]
The frequency of deep cyclones determined by the depth was higher feature of the annual cycle of extreme cyclones (Figure 3b,d) was a steeper descending slope from winter to spring months, resulting in the highest activity of these cyclones from November to March
We showed in [42] that correlation coefficients of the winter–spring Spuastraainmabeiltiteyr2s0o20f,t1h2,extFoOtaRlPnEuEmR RbEeVrIoEWf cyclones in the Black Sea region exceeded 0.6 with North Atlantic Oscillation (NAO) i1n4doifce25s, while they reached 0.49 with Southern Oscillation indices at time lags of 4–6 months, and the joint ciyncflluonenesceinofthNeAsOtuadnieddErNegSiOons.igTnhiafitcaisntwlyhyexaceseidmeidla5r0c%ororefltahtieoinntiesraenxpneucatledvawriaitbhilditeyeopf ccyycclloonneess iidnetnhteifisetdudbiyedqureagnitoilne.s.TIht actanisbwehaypausripmosilearofcorurrelfautritohnerissetuxdpyec. ted with deep cyclones identified by quantiles
Summary
Knowledge of the periods and patterns of regional climate variability is important for the development of long-term forecasts of weather and climate anomalies and for solving applied problems of long-term planning of regional sustainable development under climate change [1,2,3]. An increase of global surface temperature is generally accompanied by a decrease in the total number of extratropical cyclones and their packing density in extratropical latitudes of the northern hemisphere, for example in the North Atlantic and European region [6]. The frequency of deep cyclones over the northern hemisphere has already doubled during the most recent period of global temperature rise (after 1980) [8]. According to calculations by climatic scenarios of the global warming, the increase of cyclonic activity in the North Atlantic and Western Europe will occur until the end of the 21st century due to an increase in the frequency of cyclones formed over the Gulf Stream and an increase in the transformation of tropical cyclones into extratropical ones, which threaten Western Europe [9,10]
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