Untangling the inhibitory effect of dust aerosols on weak precipitation

Abstract As one of the most abundant and widely distributed aerosols in the troposphere, dust aerosols act as condensation nucleus to alter the life cycle of clouds and precipitation, thus affecting weather and climate. However, the effects of dust aerosols on precipitation are still not fully understood, particularly for the raindrop size distribution (DSD) of weak precipitation and thus warrant investigations. Taking multiple precipitation episodes occurring from March 15th to April 1st, 2021 in Pudong, Shanghai, China as an example, we attempt to reveal the underlying impacts of dust aerosols on weak precipitation’s DSD. Compared with the weak precipitation events with and without dust aerosols, we find that dust aerosols may inhibit weak precipitation. In details, the mean mass weighted average diameter (Dm) of dust-carrying precipitation is much smaller than the weak precipitation without dust aerosols, while the mean value of normalized intercept parameters (Log10Nw) of dust carrying precipitation is greater than the dust-free precipitation. Moreover, the dust-carrying precipitation episodes have higher (lower) number concentration of small (large) raindrops than the precipitation events without dust aerosols, demonstrating that dust aerosols could lead to a significant increase (decrease) in the number concentration of small (large) raindrops. As a results, dust aerosols are favorable to stimulate a more concentrated distribution of raindrop size and a smaller spectral width, prolonging the life of clouds and thus inhibiting weak precipitation. These findings highlight the inhibitory effect of dust aerosols on weak precipitation and can provide scientific insights for weather and climate prediction.