Cloud droplet size retrievals from AERONET cloud mode observations

Cloud droplet size is an important property not only for determining the Earth's radiative energy budget, but also for understanding interactions between clouds and aerosols. While a number of passive satellites have been routinely used to retrieve cloud droplet size, these retrievals could only represent droplet size near cloud tops. Up to now, routine size observations for near cloud bottoms remain limited. The Aerosol Robotic Network (AERONET) has operated new cloud mode observations since 2010. Among 35 cloud mode sites, 13 of them measure zenith radiances at a liquid-water-absorbing wavelength, which can be used to retrieve cloud droplet effective radii. We will present our retrieval method and demonstrate performance using simulated stratocumulus and cumulus clouds. We will also show retrievals from AERONET observations and compare them to those retrieved from other surface-based instruments.