Improvements in PSTD methods and surface roughnessmodel applied to simulation of lidar-observable optical properties of roughened hexagonal crystals.

Abstract:

Understanding the fundamental scattering properties of ice

atmospheric particles such as ice crystals and aerosol

particles in clouds is important for proper interpretation of

satellite observations and for development of radiation

parametrizations in climate models, as is well known. Also

well known are the increasingly severe CPU demands

involved in attempts to numerically simulate just single

particle scattering properties with exact methods when the

particle size parameter increases. In this talk we will show

results obtained with an improved version of our PSTD

code that makes larger particle sizes accessible than before,

together with a new model of specifying the degree of

particle surface roughness. The particular application we

concerns an issue of importance to lidar observations: the

effect of particle morphology of ice crystals on lidar ratio, backscatter, and depolarization ratio.