Remote sensing of cloud properties using MODIS airborne simulator imagery during SUCCESS 3. Cloud overlap

The vertical distribution of cloud layers has a significant effect on atmospheric radiative heating/cooling distributions. While multiple cloud layers are often observed to occur simultaneously by surface observers, satellite cloud retrieval methodology typically assumes that any individual imager pixel contains a single cloud layer. The purpose of this paper is to demonstrate a bispectral method that detects imager pixels containing possible cloud overlap when an optically thin cirrus cloud overlies a low level water cloud, with at least a 2-km separation between layers. The method is developed from a scatterplot of the near-infrared 1.63-mu m band reflectances and the 11-mu m brightness temperatures using data from the MODIS (Moderate Resolution Imaging Spectroradiometer) airborne simulator (MAS). The bispectral method is applied to a scene recorded by the MAS scanning spectrometer that was flown on the NASA ER-2 during the Subsonic Aircraft: Contrail and Cloud Effects Special Study (SUCCESS)field campaign during April and May 1996, For a scene recorded on April 21, 1996, at 2000 UTC, the complex vertical cloud structure was captured by lidar backscatter measurements from the Cloud Lidar System (CLS). The bispectral method appears to have a promising facility for identifying areas containing potential cloud overlap.