Abstract:

This study analyzes the microphysical characteristics of precipitation under acoustic intervention in China’s inland arid region, based on the results of acoustic rain enhancement experiments conducted from June to September, 2019, in a study area (37°27'36'' E, 96°48'00'' N) located in the northeastern edge of the Qaidam Basin, Qinghai Province. This region, which has an average elevation of 2980 m, has a highland continental climate and experiences year-round drought and little rain: the average annual precipitation is approximately 204.7 mm. Most of the annual precipitation typically occurs in the wet season, which lasts from June to August. The observed precipitation data were obtained using an OTT Parsivel laser raindrop spectrometer and a tipping bucket rain gauge and have been analyzed using statistical analysis and physical inspection methods to compare the microphysical characteristics of the precipitation under acoustic interference and nonacoustic interference. Furthermore, the raindrop size distribution is described by a Gamma distribution. The major contributions of this study are as follows: (1) The accumulated precipitation increased after the acoustic equipment was turned on, and the proportions of events with increased precipitation and reduced precipitation were 60.87% and 39.13%, respectively. The average values of the microphysical parameters (e.g., the average particle size, liquid water content, radar reflectivity factor, rainfall intensity, and kinetic energy) were greater by varying degrees after the acoustic equipment was turned on. The increase of the average particle size, radar reflectivity factor, and liquid water content were 3.23%, 6.12%, and 11.43%, respectively. The changes in the rainfall intensity and kinetic energy were the most obvious, with an increase of 36.00% and 69.20%, respectively. (2) The mean raindrop size distribution of the total rainfall sample changed and the shape factor of the fitted distribution decreased after the acoustic equipment was turned on. The concentration of raindrop particles increased after approximately 0.8 mm. Additionally, the analysis of the relationship between the standardized intercept parameter and the rainfall intensity after the intervention of acoustic waves shows that the particle number concentration increased with the increase in the rain intensity. (3) Regarding the rainfall intensity at different distances from the test’s origin after the acoustic equipment was turned on and off, it was found that the rain intensity value increased significantly within 3 km after the sound wave was turned on. This shows that acoustic intervention has a certain impact on the surrounding rainfall. Based on the above analysis, acoustic intervention is seen to have a significant impact on precipitation in terms of the microphysical and spatial distribution. Unlike the traditional precipitation enhancement studies that use catalyst spreading technology, this article focuses on the study of a new artificial precipitation enhancement method: acoustic precipitation enhancement. In it, a detailed analysis is undertaken of the surface precipitation microphysical characteristics, rainfall changes, and rainfall intensity distribution under acoustic interference. The results reported in this study offer a new avenue for the analysis of the microphysical characteristics of acoustic precipitation in inland arid regions, which is of value to wider acoustic precipitation enhancement experiments and their evaluation.

Key words: acoustic, precipitation enhancement, drop size distribution (DSD), microphysical characteristics of precipitation, Qaidam Basin