Satellite‐Based Detection of Secondary Droplet Activation in Convective Clouds

We present a new approach of analyzing and interpreting vertical profiles of cloud microstructure obtained by satellite remote sensing. The method is based on a spectral bin microphysics adiabatic parcel model and aims to elucidate the effects of aerosols on the evolution of convective clouds and related microphysical processes, including the activation of cloud condensation nuclei (CCN), the growth of cloud droplets, and the formation of precipitation. Characteristic features in the vertical profiles of effective radius (re) and temperature (T) reveal different microphysical zones in convective clouds related to the change increase of re with decreasing T. The classification of the different microphysical zones includes the (a) condensational growth of droplets, (b) growth by coalescence, (c) rainout, (d) secondary droplet activation zone (SAZ), (e) mixed‐phase of ice particles and water droplets, and (f) glaciation of the cloud. The detection of the SAZ is introduced here for the first time. This method allows us to identify the activation of aerosol particles above cloud base and their role in the invigoration of deep convective clouds. Plain Language Summary Using satellite remote sensing, we can obtain the vertical profiles of cloud microphysical processes in developed clouds. In this study, we present a new way of analyzing these profiles and understand the different processes that cloud droplets undergo during the development of the cloud. These processes include the turning of aerosols into cloud droplets, and the droplets' coalescence into rain drops. The change of droplets' size with height, as obtained by the satellite, reflect the different microphysical processes inside the cloud. While expecting the droplets to grow with height, a decrease of the droplets size suggests either rainout of the larger droplets from the cloud; or creation of small new droplets at much greater heights than the cloud base, where they are usually created. Those processes can be related to the extent of decrease of cloud drop size with height. The detection of new droplet formation above the cloud base with satellite is introduced here for the first time and it allows to understand this microphysical process and its effect of the development of the clouds and precipitation. Key Points A new method to interpret the cloud microstructure of deep convective clouds from satellite remote sensing is presented in this study The microphysical process of secondary activation of