A Parameterization of Infrared Radiative Properties of Cirrus/Contrails Containing Small Ice Particles

A parameterization of infrared radiative properties of cirrus clouds was developed by Fu et al. (1998), which was based on in-situ observed ice particle size adistributions with the consideration of nonspherical ice particles. This parameterization, however, is accurate when the effective ice particle size (Dge) is larger than about 10 microns (i.e., an effective radius of about 6.5 microns). For contrail cirrus and tropical tropopause subvisible cirrus, the Dge are often smaller than 10 microns. In this work, we will extend the parameterization of cirrus radiative properties for the Dge ranging from 1 to 10 microns. We will also examine the impact of the consideration of bimodal ice particle size distribution on the broadband radiative energy budget calculations.