MODAPS PCR 2004-12-09

PCR Number  
Date 2004-12-09
Initiator Lorraine Remer
Abstract Multiple changes to L2 aerosol retrieval algorithm.
Problem Statement Land: Subpixel snow causes aerosol retrievals 2 to 10 times greater than reality. Current cloud mask logic permits cloud contamination. Geographic distribution of aerosol models leads to underprediction in highly absorbing regions of Asia. Current cloud fraction not a true cloud fraction. Unnecessary SDS's still in product. Bugs in the code permit occasional land retrieval over ocean.

Ocean: Units incorrect for CCN. Cloud fraction not a true cloud fraction. Unnecessary SDS's still in product.
Description of Change 1. Subpixel snow test and mask implemented.
2. Land cloud mask logic adjusted and QA flag set to 0 in some circumstances.
3. Geographic distribution of land aerosol models adjusted to agree with observed ranges of heavily absorbing aerosol.
4. Cloud fraction redefined to be a true cloud fraction, no longer containing pixels discarded for non-cloud reasons, and a new SDS introduced to hold cloud mask by products for better understanding of the cloud mask subtleties.
5. Bugs corrected and unnecessary SDS's removed.
6. CCN units corrected.
Products Affected M[O|Y]D04_L2
Software Affected PGE04
Processing String to Receive the Change Terra Reprocessing, Aqua Reprocessing
Downstream Product Effects Atmosphere Level 3 (all products)
Data Granules to be Used for Science Testing Use Atmosphere 18-day science test data set.
Justification Users must have confidence in product on a regional as well as global basis. Regions at snow boundaries, for example, must improve. Unnecessary SDS's take up resources and should be eliminated. Aerosol-cloud studies are very important and a true cloud product to be used in these studies is necessary. Cloud contamination is a difficult issue requiring adjustment and refinement. More cloud mask diagnostics are needed to be able to evaluate the final aerosol product.
Effective Date for Implementation of Change Start of C5 Terra and Aqua Reprocessing.
Status