Arid Zone Research ›› 2024, Vol. 41 ›› Issue (10): 1615-1626.doi: 10.13866/j.azr.2024.10.01

• Weather and Climatee • Previous Articles     Next Articles

Raindrop spectral characteristics of an autumn convective precipitation on the north slope of the Qilian Mountains

FU Shuangxi1(), WANG Fucong2(), LI Baozi1, FANG Chungang3, CHEN Tianyu3   

  1. 1. Gansu Weather Modification Office, Lanzhou 730000, Gansu, China
    2. Zhangye Meteorological Bureau, Zhangye 734000, Gansu, China
    3. CMA Weather Modification Centre(WMC), Beijing 100081, China
  • Received:2023-12-25 Revised:2024-07-15 Online:2024-10-15 Published:2024-10-14
  • Contact: WANG Fucong E-mail:fusx1997@163.com;wangfucun3@yahoo.com.cn

Abstract:

This study analyzed the influence system, characteristics of the raindrop spectrum of a convective precipitation process that occurred on September 21, 2020, in the northern slopes of the Qilian Mountains using upper-air and ground data, Doppler weather radar products, and Parsivel2 laser raindrop spectrometer observation data. Results demonstrated that precipitation was affected by a short-wave trough moving eastward over the plateau and the northern border region. Liquid water content W was consistent with rain rate R, and the corresponding raindrop diameter D was <1 mm when the particle number concentration N(D) was maximum at each site, which occurs during stratiform precipitation. The raindrop diameter increased rapidly during the maximum rain intensity of convective precipitation, with the maximum diameter D being in the range of 2.75-3.75 mm at each site. The mean raindrop number concentration NT was larger at higher elevation sites than at lower elevation sites, whereas the mean mass weighted average diameter Dm was larger at lower altitude sites than at higher altitude sites. The Dm of convective precipitation was significantly larger than that of stratiform precipitation. The distributions of Dm and logNw were relatively concentrated for convective precipitation, whereas they showed larger spectral width for stratiform precipitation. The gamma function could better fit the average raindrop spectrum of convective precipitation and stratiform precipitation in the Qilian Mountains. The shape parameter µ and the slope parameter λ of the gamma fitting function satisfied the good fitting relationship in convective precipitation and stratiform precipitation. Positive fitting coefficient and exponent were observed in the relationship of Dm-R. Dm increased with the improvement of R and stabilized after the rain rate reached a certain value. The logNw of stratiform precipitation changed faster with improvement of R, and the logNw of convective precipitation increased slowly with improvement of R. The precipitation estimates of convective precipitation and stratiform precipitation were lower in the Qilian Mountains when the default Z-R relationship was used to estimate precipitation in the operational radar application.

Key words: raindrop spectrum, raindrop number concentration, mass weighted average diameter, Z-R relationship, Qilian Mountains