Notes on computation of the Fine Mode weighted Aerosol Optical Depth over Ocean:
- We extract the parameter/Science Data Set(SDS) "Optical_Depth_Land_And_Ocean_Mean" from the MOD08/MYD08 product files. This parameter contains a global [over land(corrected) and ocean (best)] monthly mean aerosol optical depth at 0.55 microns available on a 1 deg by 1 deg Climate Modeling Grid (Equal Angle Grid). The array size is thus 360X180.
- Then we extract the parameter/SDS "Optical_Depth_by_models_ocean_Mean" from the MOD08/MYD08 product files. This parameter has "Fill Values" for grid points over Land but 9 modes for grid points over Ocean. The array size is 9X360X180. The 9 modes correspond to aerosol particles as follows:
- Fine/Small Mode: Aerosol Models for particles with effective radii 0.10, 0.15, 0.20, and 0.25 µm
- Coarse/Large Mode: Aerosol Models for Marine (sea salt) particles with effective radii 1.0, 1.5, and 2.0 µm
- Coarse/Large Mode: Aerosol Models for Mineral Dust particles with effective radii 1.5 and 2.5 µm
- Fine Mode Fraction Weighted Aerosol Optical Depth at 0.55 µm at each grid point is computed as:
For Grid point at (Lat,Lon), we compute a
- Fine Mode Fraction (Lat,Lon) = ( Sum of Fine Modes(I,J)/Sum of All Modes(I,J) )
where Fine Modes = Modes 1 through 4 in (2) above.
- Fine Mode Weighted AOT = Fine Mode Fraction * Optical_Depth_Land_Ocean_Mean(I,J)
Note: This Fine Mode Weighted Optical Depth Parameter is VALID over Ocean Grid points only. This parameter contains "Fill Values" for grid points over land.
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