MODAPS PCR 2004-11-03

PCR Number  
Date 2004-11-03
Initiator Lorraine Remer
Abstract Corrected logic to allow aerosol retrievals under very clear conditions.
Problem Statement Negative values in the L1B radiances of the 1.38 µm channel are currently being categorized as "bad input data:" by the MOD04 algorithm. No aerosol retrieval is attempted on such pixels. However, the negative values indicate very small reflectance at this channel, which implies a very clear scene with no high clouds. These are good pixels. Currently we are throwing out a great many good pixels.
Description of Change We now permit small negative values of 1.38 µm, equating these values to "0", in the internal MOD04 cloud mask for aerosols.
Products Affected M[OY]D04_L2 and M[OY]05_L2
Software Affected PGE04
Processing String to Receive the Change Terra Forward, Aqua Forward
Downstream Product Effects Atmosphere Level 3 (all products)
Data Granules to be Used for Science Testing Test on one day of data, Terra or Aqua
Justification A great many good scenes go without aerosol retrieval because we currently throw out a pixel when the 1.38 µm value is negative. Our users in the Air Quality community complain that there is no aerosol data when conditions are best suited for a good retrieval (i.e. when skies are clear of clouds).
Effective Date for Implementation of Change  
Status