Distinct changes of cloud microphysical properties and height development by dust aerosols from a case study over Inner-Mongolia region

Dust aerosols, by serving as cloud condensation nuclei and/or ice nuclei, can impact the properties and development of clouds. Selecting the dust event occurred in May 2016 as a case, this study investigates the potential impacts of dust aerosols on cloud system by examining the differences in cloud properties between the dust polluted and unpolluted parts using the geostationary satellite (Himawari-8) observation data. It is found that the cloud particles effective radius (r(e)) is significantly smaller in the dust polluted region than that in unpolluted region. With the increase of dust aerosol optical depth (AOD), the cloud particle re decreases, showing a first indirect effect (IE) value (defined as -dln(r(e))/dln(dust AOD)vertical bar(CWP)) of 0.31. From the beginning of the formation of ice crystals to the complete transformation into ice crystals, compared to the polluted region, cloud particle re had a more rapid increase as the cloud top height increased in unpolluted region, which might be associated with the formation of large supercooled droplets with less ice nuclei along with the higher possibility of collision coalescence. It is also found that the increase in dust AOD likely causes the release of latent heat and the promotion of convection, which makes the cloud develop stronger to a higher position. This study reveals distinct impacts of dust aerosol on clouds from a microphysical perspective along with the potential mechanism behind the findings, which can provide observational support for improvement of cloud parameterization in numerical models