Wednesday, 15 January 2020
Hall B1 (Boston Convention and Exhibition Center)
In summer, a vast number of Meso-scale Convective Vortex (MCV) cloud clusters originate from the east slope of Tibetan Plateau and its vicinity, and propagate eastward alone the East-Asia monsoon front in the mid-lower reaches of Yangtze River thereafter, which frequently bring heavy precipitation during the eastward-propagation. Thus the microphysics characteristic of the cloud clusters is studied by analyzing the statistical results of the satellite-based observation and the microphysical processes among different hydrometeors for sake of a full comprehension of the precipitation mechanism related to the eastward-propagating MCV cloud clusters. First of all, the variation of the average precipitation intensity indicates that the rainfall triggered by the cloud clusters is likely to enhance, and the remote observation from the Cloudsat satellite shows that the proportion of convective cloud increases significantly during the eastward propagation of the cloud clusters, while the shallow cloud presents the opposite trend. Besides the number concentration of both the cloud ice crystal and the cloud liquid water increases obviously with the enhancement of precipitation intensity. More interestingly, a notable stretching upward trend is found in the distribution of the cloud ice crystal, while the distribution of cloud liquid water shows stretching downward trend on the premise that the precipitation intensity is enhanced. Then a budget calculation of each species of hydrometeor is proposed to illustrate the microphysical processes in the cloud clusters based on a representative rainstorm case triggered by the eastward-propagating MCV cloud clusters. The results show that there are three major conversion pathways that are responsible for the formation of the raindrops: the first one begins with the deposition from water vapor to cloud ice first, followed by auto conversing to graupel, and finally melting into raindrops; then the second one is the deposition from water vapor to graupel followed by melting into raindrops; and the third one is the accretion from cloud liquid water to snow followed by melting into raindrops. All these pathways confirms that the ice cloud processes will get more remarkable if the precipitation intensity is enhanced, and this discovery is in accordance with the observation from Cloudsat satellite.
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