Characteristics of Convective Clouds Producing Heavy Precipitation in Northwest Russia

Abstract

Characteristics of clouds which produced heavy precipitation in St. Petersburg and Leningrad oblast on June 18, 2020, are considered based on measurements with a C-band Doppler radar, Pluvio² 200 precipitation gauges, and a Blitzortung lightning detection system. To assess the intensity of precipitation, different values of the coefficients in the Marshall–Palmer Z–R relation are studied. We show that it is reasonable to use the specific differential phase to calculate the precipitation intensity when it exceeds 30 mm/h and precipitation consists of raindrops and hail. The top of the clouds exceeded 12 km, the maximal reflectivity was higher than 52 dBZ, and the maximal precipitation intensity could exceed 160 mm/h. A significant volume of a cloud was occupied by hail particles, which were recorded from the Earth’s surface up to an altitude of 10 km. The highest reflectance was recorded in the precipitation zone, as well as in the hydrometeors melting area. All the clouds under study were thunderstorms. A sufficiently high correlation between the frequency of lightning and the intensity of precipitation is noted: the Spearman’s correlation coefficient exceeds 0.7.