Development of Midlatitude Cirrus Models for MODIS Using FIRE-1, FIRE-II, and ARM In Situ Data

摘要

Detailed in situ data from cirrusclouds have been collected during dedicated field campaigns, but the use of the size and habit distribution data has been lagging in the development of more realistic cirrus scattering models. In this study, the authors examine the use of in situ cirrusdata collected during three field campaigns to develop more realistic midlatitude cirrusmicrophysical models. Data are used from the First International Satellite Cloud Climatology Project (ISCCP) Regional Experiwnt (FIRE)-I (1986) and FIRE-I1 (1991) campaigns and from a recent Atmospheric Radiation Measurement (ARM)Program campaign held in March-Apr of 2000. The microphysical models are based on measured vertical distributions of both particle size and particle habit and are used to develop new scattering models for a suite of moderate-resolution imaging spectoradiometer (MODIS) bands spanning visible. near-infrared, and infrared wavelengths. The sensitivity of the resulting scattering properties to the underlying assumptions of the assumed particle size and habit distributions are examined. It is found tbat thc near-infrared bands are sensitive not only to the discretization of the size distribution but also to the assumedhabit distribution. In addition. the results indicate that the effective diameter calculated from a given size distribution tends to be sensitive to the number of size bins that are used to discretize the data and also to tbe ice-crystal habit distribution.