Observational Quantification of Aerosol Invigoration for Deep Convective Cloud Lifecycle Properties Based on Geostationary Satellite

Abstract

AbstractAerosols affect cloud microstructure, dynamics, and precipitation by acting as cloud condensation nuclei (CCN) and ice nuclei with a large uncertainty for deep convective clouds (DCCs). Here, we quantify the relationships between aerosols and DCC properties after isolating aerosol impacts from meteorology based on the METEOSAT geostationary satellite and Modern‐Era Retrospective Analysis for Research and Application Version 2 (MERRA‐2) reanalysis data. Results show that fine aerosols (radius <1 µm), which serve as the best proxy for CCN from MERRA‐2, exhibit the strongest aerosol invigoration for DCC compared with aerosol optical depth and coarse aerosols. Overall, added fine aerosols result in colder cloud top temperatures (CTTs), longer lifetime, and more rainfall amounts, especially over land. As CTT decreases monotonically with added aerosols, cloud lifetime and rainfall amount reach a maximum at aerosol loading of 5 and 1.5 µg/m3 over land and ocean, respectively. Added precipitable water (PW) vapor and convective available potential energy (CAPE) are conducive to the development of more vigorous DCC. For fixed PW and CAPE, CTT decreases by up to −12.2°C ± 0.5°C with fine aerosol concentration over land and up to −4.4°C ± 1.0°C over ocean. The DCC lifetime is lengthened by a factor of 1.3 ± 0.1 from clean condition to optimal aerosol loading over land. A respective enhancement in rainfall amounts over land is indicated by a factor of 2.6 ± 0.4. The decreases in lifetime and rainfall beyond the optimal aerosol concentration are likely due to less aerosol wet scavenging from smaller and less rainy DCCs. The increases in the lifetime and rainfall amounts over ocean are much weaker.