Abstract:

Using data from the physical detection tests of aircraft clouds carried out in the Sanjiangyuan region under the “Second Comprehensive Scientific Research on Qinghai-Tibet Plateau” project, this paper analyzes the macroscopic and microphysical characteristics of a cumulonimbus cloud and its convective bubbles in the Zeku region of Sanjiangyuan on September 13, 2020. The results indicate the following: (1) the temperature inside the cumulus hybrid cloud was between -23 ℃ and -10 ℃, the relative humidity was 90%-100%, and the liquid super-cooled water was between 0.04 g·m^-3 and 0.70 g·m^-3; (2) the average particle number concentration inside the convective bubble was higher compared to the surrounding stratus cloud 10¹ L^-1, the average effective particle radius was larger, and the average liquid super-cooled water was 0.28 g·m^-3, which was higher compared to the stratus cloud at about 0.03 g·m^-3, a better correspondence between the particle number concentration and the liquid super-cooled water. Cloud particle spectra all showed multi-peak distribution, with peaks at 50 μm, 400 μm, and 1000 μm, in line with the distribution characteristics of typical high clouds. (3) The particles in cumulus mixed clouds were mostly aggregated ice crystal particles, and a small amount of hexagonal plate and linear ice crystals existed in some higher layers, with freezing and aggregation growth mechanisms dominating in the clouds and condensation growth dominating in the convective bubbles. The precipitation mechanism in the clouds was consistent with the “sowing-supply” mechanism.

Key words: aircraft measurement, microphysical characteristics, stratiform cloud with embedded convection, cloud convective generating cells, Sanjiangyuan region