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

• Published in: Atmospheric chemistry and physics 2007-01, Vol.7 (15), p.4149-4158
• Main Authors: Davis, C. P., Evans, K. F., Buehler, S. A., Wu, D. L., Pumphrey, H. C.
• Format: Article
• Language: English
• Subjects: Ocean, Atmosphere; Rymdteknik; Sciences of the Universe; Space Technology
• ISSN: 1680-7324; 1680-7316; 1680-7324
• DOI: 10.5194/acp-7-4149-2007

Global observations of ice clouds are needed to improve our understanding of their impact on earth's radiation balance and the water-cycle. Passive mm/sub-mm has some advantages compared to other space-borne cloud-ice remote sensing techniques. The physics of scattering makes forward radiative transfer modelling for such instruments challenging. This paper demonstrates the ability of a recently developed RT code, ARTS-MC, to accurately simulate observations of this type for a variety of viewing geometries corresponding to operational (AMSU-B, EOS-MLS) and proposed (CIWSIR) instruments. ARTS-MC employs an adjoint Monte-Carlo method, makes proper account of polarisation, and uses 3-D spherical geometry. The actual field of view characteristics for each instrument are also accounted for. A 3-D midlatitude cirrus scenario is used, which is derived from Chilbolton cloud radar data and a stochastic method for generating 3-D ice water content fields. These demonstration simulations clearly demonstrate the beamfilling effect, significant polarisation effects for non-spherical particles, and also a beamfilling effect with regard to polarisation.