Low-frequency change of wind fields and geostrophic flows of the Black Sea on satellite data. Part 2: the long-term tendencies

by

A.B. Polonsky1,2,3, A.N. Serebrennikov1

1Institute of Natural and Technical Systems, RF, Sevastopol

E-mail: apolonsky5@mail.ru; swsilv@gmail.com

2Branch of Moscow State University in Sevastopol, RF, Sevastopol

3Sevastopol State University, RF, Sevastopol

DOI: 10.33075/2220-5861-2019-3-60-68

UDC 551.465.7

 Abstract:

   The article presents data on the interannual variability of the wind field, geostrophic currents and the Black Sea level based on satellite data from the 80s of the 20th century to 2017. It is shown that in the last 20–30 years there has been intensification of atmospheric circulation and an increase in the vorticity of the wind field. According to the data obtained over the past 8 years the interannual variability of the wind speed module has had a slight positive linear trend, For six months of the warm period of the year (from March to September), the standard deviation (SD) of interannual variability is about 0.7 m / s and its value is evenly distributed throughout the basin. In these months, the minimum average climatic values of the surface wind speed module are also observed. In the cold period of the year, not only the average wind speed increases, but also its interannual fluctuations, with the maximum values of SD observed in the western part of the sea. The vorticity is intensified both due to an increase in the wind speed and due to changes in the structure of the wind field. Surface geostrophic currents calculated from the sea level anomalies and standard ratios of the geostrophic theory are characterized by maximum interannual variability in the vicinity of the Main Black Sea Current in the southeastern, northeastern, and northwestern parts of the sea.     Typical interannual variations in geostrophic currents are presented here at about 7 cm / s. Long-term trends in the speed of geostrophic currents on the sea surface are insignificant. The rate of rise of the Black Sea level, averaged over the entire period of satellite observations, is about 2 mm / year, i.e. it is close to typical growth rate in the oceans.

Keywords: interannual variability and trends in the fields of wind and geostrophic currents of the Black Sea, trends in sea level changes.

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