Study of cloud-aerosol interactions and mixing processes in the clear-to-cloud transition zone using ARM Shortwave Spectrometers

Description

The transition zone between cloudy and clear air is a region of strong aerosol-cloud interactions where aerosol particles humidify and swell when approaching the cloud, while cloud drops evaporate and shrink when moving away from the cloud. This is an ideal region for observations of mixing/entrainment of cloud and dry air. Studying cloud and aerosol properties in the transition zone helps to better understanding of cloud-aerosol interactions and mixing processes; thus it improves the accuracy of climate models and radiation budget estimates. One-sec-resolution ARM shortwave spectrometers data provide a unique opportunity to study the transition zone. We use a developed by us earlier spectrally invariant method to analyze variations of cloud properties in transition zones observed in ARM field campaigns. Our initial results show that in most cases cloud droplet sizes remain unchanged near cloud edges. This implies that during cloud-clear sky transition the inhomogeneous mixing dominates. Our further analysis will use shortwave spectrometer data to study the factors (such as the relative humidity and aerosol properties) that affect mixing processes.