Abstract:

Through laboratory experiments, the characteristics of microphysical changes of microdroplet clusters under acoustic wave intervention were explored, the relationship between the characteristic particle size of droplet clusters and the radar reflectivity factor was established, and the quantitative relationship between the increment of particle size and the macroscopic rain intensity increment was discussed. The results reveal the following: (1) Optimal acoustic frequencies and critical sound pressure levels are observed. The experiments focused on clusters of drops with 120 Hz acoustic frequencies and exceeding the critical sound pressure level. The acoustic intervention causes the characteristic particle size of the microdroplets to increase, the right shift of the particle size spectrum to widen, the particle number concentration to decrease, and the radar reflectivity factor to increase. This conclusion is also applicable to the 30-280 Hz acoustic wave range. (2) The correlation coefficient of D₉₀-Z is above 0.9, indicating that large particle sizes considerably contribute to the radar reflectivity factor. The fitting parameters a and b are in the ranges of [2.84×10^-8, 1.104] and [0.6713, 9.2000], respectively. (3) The characteristic particle size increment of the droplets is linearly positively correlated with the macroscopic rain intensity increment, with correlation coefficients all above 0.98. In addition, as the sound pressure level increases, the linear slope of the fitting decreases. This study provides a substantial reference and guiding value for evaluating field test effects.

Key words: sound wave, microdroplets, critical sound pressure level, particle size spectrum, radar reflectivity factor