Impact of mineral dust on summertime precipitation over the Taiwan region

Abstract:

Mineral dust particles are effective ice nuclei and are known to affect cloud and precipitation. In this study, the possible impacts of mineral dust aerosols on summertime cloud and precipitation over the Taiwan region are investigated through analysis of 25 years (1989 – 2013) of multiple observational and modeling datasets. Due to the unique mechanism, typhoon precipitations are excluded in this study. Statistical methods (partial correlation and stratification) are used to untangle the influences of dust from the co-varying meteorological conditions (water vapor, horizontal wind, sea surface temperature and moisture flux). The results suggest a statistically significant positive correlation between non-typhoon precipitation and number concentration of dust particles larger than 0.5 µm (N_d) in July and August in the regions with heavy precipitation. From clean (N_d = ~0.008 cm^-3) to dusty days (N_d =~0.2 cm^-3), averaged ice (liquid) water paths and precipitation increase by ~25% (~20%) and ~70% over the orographic region, and vertically, ~30% more cloud ice content is generated at ~ 350 hPa (T = ~−20℃), enhancing the development of the mixed-phase cloud and precipitation. The results also indicate critical role of the atmospheric water vapor in the responses of precipitation to N_d, with precipitation increasing more significantly with N_d in higher water vapor circumstances.