3-D polarised simulations of space-borne passive mm/sub-mm midlatitude cirrus observations: a case study

[摘要] Global observations of ice cloudsare needed to improve our understanding of theirimpact on earth's radiation balance and the water-cycle.Passive mm/sub-mm has some advantages compared to other space-bornecloud-ice remote sensing techniques.The physics of scattering makesforward radiative transfer modelling for such instruments challenging.This paper demonstrates the ability of a recently developed RT code,ARTS-MC, to accurately simulateobservations of this type for a variety ofviewing geometries corresponding to operational (AMSU-B, EOS-MLS) andproposed (CIWSIR) instruments.ARTS-MC employs an adjoint Monte-Carlo method, makesproper account of polarisation, and uses 3-D spherical geometry.Theactual field of view characteristics for each instrument are alsoaccounted for.A 3-D midlatitude cirrus scenario is used, whichis derived from Chilbolton cloud radar data and a stochastic methodfor generating 3-D ice water content fields.These demonstration simulations clearly demonstrate thebeamfilling effect, significant polarisation effects fornon-spherical particles, and also a beamfilling effect with regard topolarisation.

[学科分类] 大气科学