Investigation of precipitation characteristics under the action of acoustic waves in the source region of the Yellow River

Abstract

Acoustic agglomerations have increasingly attracted widespread attention as a cost-effective and environmentally friendly approach for fog removal and weather modification. In this study, research on precipitation interference and the agglomeration performance of droplet aerosols under large-scale acoustic waves was presented. In total, 49 field experiments in the source region of the Yellow River (SRYR) in the summer of 2019 were performed to reveal the influences of acoustic waves on precipitation, such as the radar reflectivity factor (Z), rain rate (R), and raindrop size distribution (DSD). A monitoring system that consisted of rain gauges and raindrop spectrometers was employed to monitor near-ground rainfall within a 5 km radius of the field site. The ground-based observations showed that acoustic waves could significantly affect the rainfall distribution and microstructure of precipitation particles. The average values of rainfall increased by 18.98%, 10.61%, and 8.74% within 2 km, 3 km and 5 km of the operation center with acoustic application. The changing trend of microphysical parameters of precipitation was roughly in line with variation of acoustic waves for stratiform cloud. Moreover, there was a good quadratic relationship between the spectral parameters λ and μ. Raindrop kinetic energy (eK) and the radar reflectivity factor (Z) both exhibited a power function relationship with the rain rate (R).

Will the ‘evapotranspiration paradox’ phenomenon exist across China in the future?

“…The most common ‘evaporation paradox’ is defined as a decline in evaporation with an increase in temperature, the pan evaporation paradox is observed in several countries (Brutsaert & Parlange, 1998; Gao et al, 2006, 2007, 2012; Ning et al, 2016; Peterson et al, 1995; Liu et al, 2018; Roderick & Farquhar, 2002; Scheff & Frierson, 2014; Shi et al, 2018; Thomas, 2000; Tomas et al, 2020; Xing et al, 2014, 2016; Yin, Wu, Chen, & Dai, 2010; Yin, Wu, & Dai, 2010). In this paper, the ‘evapotranspiration paradox’ term is demarcated based on the following circumstances: (Type I) the surface temperature increases but the evaporation decreases, and (Type II) the temperature decreases but the evaporation still tends to increase; however, if the ET increases (decrease) simultaneously with the temperature, no ‘evapotranspiration paradox’ exists.…”

“…In Southwest China, the PET decreased significantly during 1960–2013, but it increased rapidly after 2000 (Zhao et al, 2018). The ‘evapotranspiration paradox’ is also reported to exist in the Yellow River region, Haihe region and Heihe region of China (Gao et al, 2012; Liu et al, 2018; Shi et al, 2018; Xing et al, 2014). Many of the previous studies using historical datasets revealed an obvious decrease in PET over time with a substantial impact on water resources and agricultural production (Liu et al, 2018).…”

Investigation of critical response characteristics of micro-droplets under the action of low-frequency acoustic waves

“…Given the width of DSSR obtained in this study, acoustic intervention with variable frequency was recommended to obtain better agglomeration performance. Thus, sweepfrequency acoustic intervention was applied to on-site artificial precipitation enhancement (Shi et al, 2021a;Shi et al, 2021b;Wei et al, 2021). Frontiers in Environmental Science frontiersin.org…”

“…One effective way to improve atmospheric quality is to eliminate the harmful aerosols by technical approaches (Dass et al, 2021;Meng et al, 2021). Acoustic agglomeration technology has great potential in the removal of fine particulate matters and the precipitation enhancement (Zhou et al, 2016;Zhang et al, 2018;Shi et al, 2021b;Wei et al, 2021) due to its safety and convenience. Dynamic reactions of fluid-particle/droplet and particle/droplet was induced and intensified by acoustic waves through inputting external energy (Yang and Fan, 2014).…”