Spatial Heterogeneity of Aerosol Effect on Liquid Cloud Microphysical Properties in the Warm Season Over Tibetan Plateau

The effect of aerosol on liquid cloud microphysical properties over the Tibetan Plateau (TP) during the warm season is investigated by using aerosol index (AI) and cloud property parameters data. Distinct differences in aerosol effect on liquid cloud microphysical properties have been found between the northern Tibetan Plateau (NTP) and southernTibetan Plateau (STP). The composite liquid cloud droplet effective radius liquid cloud droplet effective radius (LREF) anomalies for positive AI events are positive in the NTP and negative in the STP. In both NTP and STP, when the AI anomalies are positive, the LREF anomalies are also positive, which suggests that the increased aerosol loading reduces the solar radiation reaching the ground and thus enhances the atmospheric stability, which reduces the cloud base height and makes the liquid cloud area thicker, which gives cloud droplets more space to grow by collision-coalescence. This indicates that the aerosol radiative effect is not likely the reason causing the distinct differences of aerosol effects on liquid cloud properties between NTP and STP. Further analysis shows that in the STP, the LREF first increases and then decreases with the increase of AI, while in the NTP, the LREF always increases with the increase of AI, suggesting a spatial difference in aerosol microphysical effect. In the STP, the influence of aerosol on liquid clouds is mainly dependent on liquid water path and convective available potential energy, while in the NTP, the influence of aerosol on liquid cloud is more likely related to large aerosol particles. Plain Language Summary This study shows that the influence of aerosols on liquid clouds over the Tibetan Plateau (TP) in the warm season is different between the southern Tibetan Plateau (STP) and northern Tibetan Plateau (NTP). Aerosol influences the microphysics of liquid cloud over the TP through its radiative and microphysical effects. Aerosols show the uniform radiative effect over the STP and NTP, more aerosols reduce the solar radiation reaching the ground, resulting in a lower cloud base and then more space for cloud droplets to grow. Over the STP, the liquid cloud droplet effective radius (LREF) increases first and then decreases with the increase of aerosol; over the NTP, the LREF increases with the increase of aerosols, which reflects the different microphysical effects of aerosols under different meteorological conditions and aerosol types.