1Jet propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
2National Center for Atmospheric Research, Boulder, Colorado, USA
3Science and Technology Corporation, Columbia, Maryland, USA
4NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
5Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, USA
Abstract. Satellite observations show that ice cloud effective radius (re) increases with ice water content (IWC) but decreases with aerosol optical thickness (AOT). Using least-squares fitting to the observed data, we obtain an analytical formula to describe the variations of re with IWC and AOT for several regions with distinct characteristics of re-IWC-AOT relationships. As IWC directly relates to convective strength and AOT represents aerosol loading, our empirical formula provides a means to quantify the relative roles of dynamics and aerosols in controlling re in different geographical regions, and to establish a framework for parameterization of aerosol effects on re in climate models.