Comparison of Standard and NRT Products

In order to generate data products within 3 hours of observation time, a number of changes have been made to standard processing approach to expedite the availability of input data sets. First, the entrained Terra attitude and ephemeris data are used as opposed to the FD product for standard processing. Second, the rate-buffered GBAD Aqua attitude and ephemeris data are used as opposed to the 24-hour EMOS product for standard processing. Third, certain L2 codes have modified production rules to relax the requirements for ancillary data products. This is illustrated in the chart below. The L2 codes will search back in time for ancillary data a maximum of the times indicated on the arrows. The production rules used for Cloud Mask/Profiles and L2 Clouds were developed by the University of Wisconsin for their near-real time production. The production rules for L2 Aerosols were used in the standard processing for near-real time support of the ARCTAS campaign. The L2 Fire, Snow, and Sea Ice codes do not make use of ancillary data products and these codes are identical to the ones used in standard operations. A special version of the L2 Land Surface Reflectance for near-real time use was developed by the PI; this code uses the NOAA GFS ancillary product as opposed to GDAS used in the standard processing version.

Product Dependencies on Ancillary Data

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The near-real time PGE codes were extensively science tested and all products were compared to the baseline products generated by the standard processing. This comparison was made by the atmospheres and land QA (LDOPE) staff and by the PIs. All PGEs have been validated for use in LANCE-MODIS by the PIs. This process will be repeated as new versions of the PGEs become available and are considered for inclusion in LANCE-MODIS.

Two examples of side-by-side comparisons of the standard and near-real time products are shown below. The first shows a Land Surface Reflectance granule over the Midwest. There appears to be no difference between the products. However, under close examination the near-real time view shows slightly more haze West of the Great Lakes. In contrast, the second side-by-side comparison is for Cloud Top Temperature for the same granule and there are very obvious differences in the region West of the Great Lakes. This is as a result of the sensitivity of this product to the GDAS ancillary data.

Comparison of Standard and NRT Products (Land Surface Reflectance)

Comparison of Standard and NRT Products (Cloud Top Temperature)

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