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Abstract: Merging MODIS Terra and Aqua Level 3 Aerosol Optical Thickness for Giovanni Online Data Analysis and Visualization

2007 AGU Fall Meeting, December 10-14,San Francisco, CA

Merging MODIS Terra and Aqua Level 3 Aerosol Optical Thickness for
Giovanni Online Data Analysis and Visualization

Viktor Zubko, Gregory Leptoukh, Arun Gopalan

With a vast amount of satellite-obtained environmental data held, the Goddard Earth Sciences Data and Information Services Center (GES DISC) researches ways to combine multi-sensor data to increase their usefulness, and to integrate it in the GES DISC Interactive Online Visualization and Analysis Infrastructure (Giovanni). Here, we studied the performance of various methods for merging-interpolating the Moderate Resolution Imaging Spectroradiometer (MODIS) Terra and Aqua Level 3 Aerosol Optical Thickness (AOT). To quickly validate the accuracy of the merger, we introduced two confidence functions, which characterize the percentage of the merged AOT pixels as a function of the relative deviation of the merged AOT from original Terra and Aqua AOTs in respect to the original AOT standard deviations or AOT means.

Experiment with three different methods for pure merging (no interpolation): simple arithmetic averaging (SIM), maximum likelihood estimate (MLE), and weighting by pixel counts (WPC) demonstrated the relative proximity of the resulting AOTs produced by the three methods with the MLE (SIM) being slightly preferable when validating with respect to AOT standard deviations (AOT means). Another experiment with eight different methods of combined merger-interpolation applied to a variety of scenes with different gap patterns showed that that the absolutely best method is when the merging of Terra and Aqua AOTs is done first followed by Optimal Interpolation to fill in the gaps. The sensitivity of the results to the gap patterns and radius of influence was assessed.

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