A survey of tropical and mid-latitude cirrus particle size and shape using ATSR-2 visible/near infrared data

P.D.Watts and A.J.Baran


The visible (0.55, 0.67 and 0.87 micron) and near-infrared (1.6 micron) 
channels of the Along Track Scanning Radiometer are capable of determining 
the optical depth, the size and to some extent the shape of cirrus cloud 
crystals. An addition, the along track view of the ATSR allows cloud height 
determination and cloud temperature can be derived from the thermal channels 
(11 and 12 micron). We briefly describe the retrieval of these cloud 
properties, using representative ice crystal phase functions such as
hexagonal columns, plates and polycrystals, from the ATSR-2 data and their 
likely errors. 

We present results of a preliminary survey of cirrus cloud properties from 
areas of tropical convection and from midlatitude frontal cirrus. The cloud top
temperatures of our survey are consistent with more recent in-situ field
campaigns such as CEPEX and EUCREX which measured ice crystal shape and size. 
We are therefore able to compare our retrievals with measurements of ice
crystal shape and size made during those campaigns we will show the results of
such comparisons.

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry