ИСТИНА

The acoustic remote sensing allows measuring of wind profiles and some parameters of the atmospheric turbulence with high accuracy and, besides, indirect indication of the thermal stratification. As is known conditions of calm and strong inversions at low heights are dangerous regarding high atmospheric pollution in big cities. At Moscow University Meteorological observatory two sodars are operating continuously: vertical sodar ‘ECHO-1’ by GDR production since 1988 and Doppler sodar ‘MODOS’ by METEK (Germany) production since 2004. Sodar data about stratification are available in the air layer from 25 to 800 m; about wind profiles – from 40 to 500 m. It was found that a probability of surface and elevated inversions in Moscow, according to the long-term sodar data, are 37 and 18%, respectively; of unstable stratification – 17%; of neutral or slightly stable stratification – 46%. The longest elevated subsidence inversion, which was detected by the sodar below 800 m, existed from 21st to 25th November, 2005 during 103 hours continuously. The wind speed by the sodar data in 2004–2016 grows on average from 4 to 9 m/s at the heights from 40 to 300 m. The recordable high wind velocity on average of 10 min by the sodar data is 35 m/s, but cases of so strong wind (usually – close to 500 m) are extremely rare and connected as a rule with two conditions: a location of Moscow at zones of intensive gradient winds on the periphery of vast and deep cyclones and, besides, the local low-level jet stream in the wind profile. The wind speed annual course is noted as a rule by maximal values in autumn and winter (when European Russia is often located in the zones of intense gradient currents), and the minimal ones in summer. The most frequent wind direction in Moscow is West-South-Western. The average right (clockwise) wind shear in the air layer of 40–500 m is 20°. However, at some specific synoptic conditions (fronts, inclined axes of ridges and troughs, saddles) the vertical wind shear may reach 250°in the lower 300-meter air layer. This work was supported by the Russian Science Foundation (No.16-17-10275).