MODIS Direct Broadcast AEROSOL Output Product Description -------------------------------------------------------- The IMAPP MODIS aerosol softwrte creates the MODIS aerosol product, which consists of these 6 arrays at a resolution of 10x10 1 km MODIS pixels for daytime only scenes. Latitude Longitude Optical_Depth_Land_And_Ocean - AOT at 0.55 micron for both ocean (best) and land (corrected) Optical_Depth_Ratio_Small_Land_And_Ocean - Ratio of small mode optical depth at 0.55 micron Corrected_Optical_Depth_Land (3 bands) - Corrected optical thickness at 0.47, 0.55, and 0.66 micron Effective_Optical_Depth_Average_Ocean (7 bands) - AOT at seven bands for average solution at .47, .55, .66, .86, 1.2, 1.6 and 2.1 micron For a description of the algorithm, please see: Algorithm for Remote Sensing of Tropospheric Aerosol from MODIS: Collection 5. Algorithm Theoretical Basis Document, November 2006. http://modis-atmos.gsfc.nasa.gov/_docs/MOD04:MYD04_ATBD_C005_rev1.pdf Levy, R. C., L. Remer, S. Mattoo, E. Vermote, and Y. J. Kaufman, 2007: Second-generation algorithm for retrieving aerosol properties over land from MODIS spectral reflectance. J. Geophys. Res. (In press) The native IMAPP format is binary, however software is included which will convert the file from binary to HDF. Please see instructions in the imapp_modisl2/src/aerosol/README_AEROSOL file. The user can choose the output format type, either HDF or binary files. If you are using the modis_level2.csh script, you set the OUTPUT_TYPE environmental variable in the imapp_modisl2/env scripts to: 1 = binary only 2 = hdf only 3 = binary and hdf Binary Output ------------- The Direct Broadcast binary aerosol output file differs from the operational MOD04 output file in that: 1) It is a 4 byte float binary flat file instead of HDF. All parameters (bands) are of type 4 byte float. A set of routines are included if you wish to produce an HDF file. 2) There is a .img and two .hdr files representing only 6 operational MOD04 HDF SDS's listed below. 3) There are no solar and viewing geometry parameters included as part of the Direct Broadcast product (Latitude / Longitude arrays are included). 4) The output product consists of 14 band interleaved parameters instead of individual HDF file SDS's. 5) Only 6 parameters are included. The 6 are: Latitude Longitude Optical_Depth_Land_And_Ocean - AOT at 0.55 micron for both ocean (best) and land (corrected) Optical_Depth_Ratio_Small_Land_And_Ocean - Ratio of small mode optical depth at 0.55 micron Corrected_Optical_Depth_Land (3 bands) - Corrected optical thickness at 0.47, 0.55, and 0.66 micron Effective_Optical_Depth_Average_Ocean (7 bands) - AOT at seven bands for average solution at .47, .55, .66, .86, 1.2, 1.6 and 2.1 micron 6) There is no quality assurance array or file included with this delivery. -------------------------------------------------------------------------- The aerosol output product consists of a separate .img file in flat binary format, and accompanying header file. The mod04.img file is a 14 float band interleaved product at 10x10 1km pixel resolution. Please see a list of these bands below. The bands correspond to six DAAC Production HDF MOD04 product SDS's. The test output file that you create from the input test data sets contains the nominal MODIS swath size 135 (1354/10 elements) and 289 lines (2890 lines/10). Therefore, the product mod04.img file is 135 elements, by 14 bands (parameters), by 289 lines. In FORTRAN, it would be read as aerosol(135,14,289). This would be reversed in C - aerosol(289,14,135). -------------------------------------------------------------------------- MODIS Direct Broadcast Aerosol Output Product Description ------------------------------------------- Four byte float data 14 parameters 10x10 1km-pixel resolution Band Interleaved fill value = -327.68 band names = { band 1: Latitude, band 2: Longitude, band 3: Optical_Depth_Land_And_Ocean, band 4: SDS_ratio_small_Land_Ocean, band 5: Corrected_Optical_Depth_Land_.47micron, band 6: Corrected_Optical_Depth_Land_.55micron, band 7: Corrected_Optical_Depth_Land_.66micron, band 8: Effective_Optical_Depth_Average_Ocean_.47micron, band 9: Effective_Optical_Depth_Average_Ocean_.55micron, band 10: Effective_Optical_Depth_Average_Ocean_.66micron, band 11: Effective_Optical_Depth_Average_Ocean_.86micron, band 12: Effective_Optical_Depth_Average_Ocean_1.2micron, band 13: Effective_Optical_Depth_Average_Ocean_1.6micron, band 14: Effective_Optical_Depth_Average_Ocean_2.1micron } band units = { band 1: deg, band 2: deg, band 3: , band 4: , band 5: , band 6: , band 7: , band 8: , band 9: , band 10: , band 11: , band 12: , band 13: , band 14: } HDF OUTPUT FILE --------------- The HDF output file (*mod04.hdf) contains 6 arrays mentioned above. All but the latitude and longitude files are stored as short integers scaled by .001 (multiply by .001 to get correct value). (Example ncdump -h for an IMAPP aerosol hdf file) dimensions: fakeDim0 = 487 ; fakeDim1 = 135 ; fakeDim2 = 487 ; fakeDim3 = 135 ; fakeDim4 = 487 ; fakeDim5 = 135 ; fakeDim6 = 487 ; fakeDim7 = 135 ; fakeDim8 = 3 ; fakeDim9 = 487 ; fakeDim10 = 135 ; fakeDim11 = 7 ; fakeDim12 = 487 ; fakeDim13 = 135 ; variables: float Latitude(fakeDim0, fakeDim1) ; Latitude:units = "Degrees_north" ; Latitude:scale_factor = 1. ; Latitude:add_offset = 0. ; Latitude:valid_range = -90.f, 90.f ; Latitude:_FillValue = -999.f ; float Longitude(fakeDim2, fakeDim3) ; Longitude:units = "Degrees_east" ; Longitude:scale_factor = 1. ; Longitude:add_offset = 0. ; Longitude:valid_range = -180.f, 180.f ; Longitude:_FillValue = -999.f ; short Optical_Depth_Land_And_Ocean(fakeDim4, fakeDim5) ; Optical_Depth_Land_And_Ocean:units = "none" ; Optical_Depth_Land_And_Ocean:scale_factor = 0.001 ; Optical_Depth_Land_And_Ocean:add_offset = 0. ; Optical_Depth_Land_And_Ocean:valid_range = 0s, 5000s ; Optical_Depth_Land_And_Ocean:_FillValue = -9999s ; short Optical_Depth_Ratio_Small_Land_And_Ocean(fakeDim6, fakeDim7) ; Optical_Depth_Ratio_Small_Land_And_Ocean:units = "none" ; Optical_Depth_Ratio_Small_Land_And_Ocean:scale_factor = 0.001 ; Optical_Depth_Ratio_Small_Land_And_Ocean:add_offset = 0. ; Optical_Depth_Ratio_Small_Land_And_Ocean:valid_range = 0s, 1000s ; Optical_Depth_Ratio_Small_Land_And_Ocean:_FillValue = -9999s ; short Corrected_Optical_Depth_Land(fakeDim8, fakeDim9, fakeDim10) ; Corrected_Optical_Depth_Land:units = "none" ; Corrected_Optical_Depth_Land:scale_factor = 0.001 ; Corrected_Optical_Depth_Land:add_offset = 0. ; Corrected_Optical_Depth_Land:valid_range = 0s, 5000s ; Corrected_Optical_Depth_Land:_FillValue = -9999s ; short Effective_Optical_Depth_Average_Ocean(fakeDim11, fakeDim12, fakeDim1 3) ; Effective_Optical_Depth_Average_Ocean:units = "none" ; Effective_Optical_Depth_Average_Ocean:scale_factor = 0.001 ; Effective_Optical_Depth_Average_Ocean:add_offset = 0. ; Effective_Optical_Depth_Average_Ocean:valid_range = 0s, 5000s ; Effective_Optical_Depth_Average_Ocean:_FillValue = -9999s ;