Sudden and significant changes in the brightness temperature field within a given FOV pose a significant challenge to product retrieval. The effect, also known as the sub-pixel effect, is particularly pronounced in the microwave where land meets open water. The rapid change in surface emissivity along coastlines can fool a retrieval algorithm by creating false signatures that may resemble other surface types or even precipitation. Screening procedures commonly deal with edge effects by blocking out FOVs where the fraction of land or water is less than 80 percent. The black areas near the coastlines indicate blocked out FOVs.

Refer to the previous page for a summary of the important characteristics related to scanning for AMSU and SSM/I.