Model simulation of the aerosol perturbation on the Tibetan Plateau convective precipitation

The Tibetan Plateau (TP) is important for weather and climate. Relatively clean aerosol conditions over the Plateau makes the study on the aerosol-cloud-precipitation interactions in this region distinctive. A convective event with precipitation observed on 24 July 2014 in Naqu was selected to explore the influence of aerosols on the onset and intensity of precipitation. We use the Modern-Era Retrospective analysis for Research and Applications Version 2 (MERRA-2) reanalysis to derive the cloud condensation nuclei (CCN), which can be regarded as the real-time background. These values are adopted to initialize the regional WRF 4.0 meteorological model and to simulate the onset of convective events and the formation of precipitation. Four sets of experiments were adopted for our simulations. A detailed analysis of microphysical processes shows that, with the increase in the aerosol number concentration, the conversion rate of cloud water to rain in clouds is enhanced at first. Under polluted situation, the conversion process of cloud water to rain is suppressed; however, the transformation of cloud water to graupel and the development of convective clouds are favored. As a result, the onset of the precipitation is delayed and cold-rain intensity increases.