Observation and Analysis of Microphysical Characteristics of Stratiform Clouds with Embedded Convections in Yunnan

Abstract

observation is an important mean to obtain cloud physical information, which is important for weather modification research and operation. In China, aircraft observation research on cloud microphysical characteristics is mainly carried out in the northern region, seldom in the southwestern region. Yunnan is a low-latitude plateau with complex topography and distinct weather and climate. The aircraft cloud physical detection equipment in Yunnan is put into use since 2017, and it carried domestic laser cloud particle probes, including cloud particle spectrometer probe, cloud particle imager probe, and precipitation particle imager probe.The aircraft can obtain the size and number of cloud particles and precipitation particles at different resolutions of 2-6200 μm, as well as 25-6200 μm particle images.The mixed cloud observations of cumulonimbus and stratiform clouds from Yun-12 and King Air-E350 aircraft in Yunnan during 2017-2020 are analyzed. Data of 76 flights are obtained, with the maximum flight altitude of 6946 m (ambient temperature -14℃). The cloud vertical structure is observed by descending and ascending flights. The results show that the number concentration of cloud particles is much higher than that in northern China. The average number concentration of cloud particles (2-50 μm) is 339.7 cm-3 with a maximum value of 1067.6 cm-3; the average water content is 0.181 g·m-3, and the maximum is 2.827 g·m-3; the average effective diameter of cloud particles is 11.2 μm and the maximum is 34.6 μm. The cloud particles have a negative exponential size distribution with double peaks. The first peak is located at 4 μm and the second peak is at 10 μm. The cloud particle number concentration, water content and extinction coefficient show obvious layered distribution characteristics with height, but the effective particle diameter doesn't change much.The reflectivity factor is maximum at the height of 3.4 km.In the warm cloud region, the average water content of rain drops with diameter from 200 to 1500 μm is 0.183 g·m-3 with a maximum value of 4.247 g·m-3. The average water content of rain particles in the range of 200-6000 μm is 0.406 g·m-3 with the maximum of 8.917 g·m-3.In Yunnan, the spectral width of cloud particles becomes wider with the increase of cloud water content.With the outbreak and establishment of the Southwest Summer Monsoon, the small cloud particles increase, and the large cloud particles decrease in the warm area of cloud. It is helpful to improve the efficiency of artificial precipitation enhancement by carrying out warm cloud artificial precipitation enhancement.

Keywords

• cloud microphysical properties
• aircraft measurements