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MOD04_L2
Introduction
Format & Content
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QA Information
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Format & Content

File Format Basics

MOD04_L2 product files are stored in Hierarchical Data Format (HDF). HDF is a multi-object file format for sharing scientific data in multi-platform distributed environments. HDF files should only be accessed through HDF library subroutine and function calls, which can be downloaded from the HDF web site. Each of the 53 gridded parameters listed below is stored as a Scientific Data Set (SDS) within the HDF file.

Note: We are permitting small negative Aerosol Optical Depth values in order to avoid an arbitrary negative bias at the low AOD end in long term statistics. This is because MODIS does not have sensitivity over land to retrieve aerosol to better than +/-0.05. This means in very clean conditions the algorithm cannot determine if the AOD = 0, 0.05 or -0.05. If we eliminate all the negative numbers and keep all the positive numbers, we introduce an artificial bias. Thus, we allow negative retrievals up to -0.05. To interpret these: If you are calculating long-term statistics, simply add the negatives into the mix and don't worry about them. If you were looking at individual retrievals then count negative retrievals as 'very clean'. You could force them to be AOD = 0, for example. It really depends on the application. However, these small negative AOD values are good retrievals and do contain information.




MOD04_L2 Dimension List   (Collection 051)

  1. Cell_Along_Swath = 203 (typical size)
  2. Cell_Across_Swath = 135 (typical size)
  3. Solution_1_Land = 2 (470, 659 nm)
  4. Solution_2_Land = 3 (470, 555, 659 nm)
  5. Solution_3_Land = 3 (470, 659, 2130 nm)
  6. Solution_4_Land = 4
  7. Solution_Index = 9 (1, 2, 3, 4, 5, 6, 7, 8, 9)
  8. Solution_Ocean = 2 (1, 2)
  9. MODIS_Band_Land = 7 (470, 555, 659, 865, 1240, 1640, 2130 nm)
  10. MODIS_Band_Ocean = 7 (470, 555, 659, 865, 1240, 1640, 2130 nm)
  11. Num_By_Products = 7
  12. Num_DeepBlue_Wavelengths = 3
  13. QA_Byte_Land = 5
  14. QA_Byte_Ocean = 5
  15. Number_of_Instrument_Scans = 203 (typical size)
  16. Maximum_Number_of_1km_Frames = 1354 (typical size)



MOD04_L2 Scientific Data Set (SDS) List   (Collection 051)


    Geolocation and Time Parameters

  1. Longitude
      Description: Geodetic Longitude
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: -180 to +180 degrees east
  2. Latitude
      Description: Geodetic Latitude
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: -90 to +90 degrees north
  3. Scan_Start_Time
      Description: International Atomic Time at Start of Scan replicated across the Swath
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0.0 to 3.1558E+9 seconds since 1 January 1993 00:00:00



    Solar and Viewing Geometry Parameters

  4. Solar_Zenith
      Description: Solar Zenith Angle, Cell to Sun
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0 to +180 degrees
  5. Solar_Azimuth
      Description: Solar Azimuth Angle, Cell to Sun
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: -180 to +180 degrees
  6. Sensor_Zenith
      Description: Sensor Zenith Angle, Cell to Sensor
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0 to 180 degrees
  7. Sensor_Azimuth
      Description: Sensor Azimuth Angle, Cell to Sensor
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: -180 to 180 degrees



    Science Parameters


      Combined Land and Ocean

  8. Scattering_Angle
      Description: Scattering Angle
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0 to 180 degrees

  9. Optical_Depth_Land_And_Ocean
      Description: Aerosol Optical Thickness at 0.55 µm for both Ocean (best) and Land (corrected) with best quality data (QA Confidence Flag = 3)
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: -0.05 to 5.0

  10. Image_Optical_Depth_Land_And_Ocean
      Description: Aerosol Optical Thickness at 0.55 µm for both Ocean (best) and Land (corrected) with all quality data (QA Confidence Flag = 1,2,3)
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: -0.05 to 5.0

  11. Optical_Depth_Ratio_Small_Land_And_Ocean
      Description: Ratio of small mode optical depth at 0.55 µm
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0.0 to 1.0



      Land Only

  12. Aerosol_Type_Land
      Description: Aerosol Type
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0 to 4    (0=mixed, 1=dust, 2=sulfate, 3=smoke, 4=heavy absorbing smoke)
  13. Fitting_Error_Land
      Description: Fitting Error for Land
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0 to 1.0
  14. Surface_Reflectance_Land
      Description: Fitting Error for Land
      Dimensions: (Solution_2_Land, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0 to 5.0
  15. Corrected_Optical_Depth_Land
      Description: Corrected Optical Thickness at 0.47, 0.55, and 0.66 µm
      Dimensions: (Solution_3_Land, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: -0.05 to 5.0
  16. Corrected_Optical_Depth_Land_wav2pl
      Description: Corrected Optical Thickness at 2.13 µm
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: -0.05 to 5.0
  17. Optical_Depth_Small_Land
      Description: Corrected Optical Thickness for small mode at 0.47, 0.55, 0.66, and 2.13 µm
      Dimensions: (Solution_4_Land, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: -0.05 to 5.0
  18. Optical_Depth_Ratio_Small_Land
      Description: Small mode aerosol fraction
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0 to 1
  19. Number_Pixels_Used_Land
      Description: Number of good pixels used for retrieval at 470 and 659 nm
      Dimensions: (Solution_1_Land, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 1 to 400
  20. Mass_Concentration_Land
      Description: Mass Concentration over Land
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0 to 1000 x 1.0e-6g/cm^2
  21. Angstrom_Exponent_Land
      Description: Angstrom Exponent at 0.47 and 0.67 µm
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: -1.0 to 5.0
  22. Cloud_Fraction_Land
      Description: Cloud Fraction from Land Aerosol Cloud Mask from retrieved and overcast pixels not including cirrus mask
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0.0 to 1.0
  23. Mean_Reflectance_Land
      Description: Mean reflectance at 0.47, 0.55, 0.66, 0.87, 1.24, 1.64, and 2.13 µm
      Dimensions: (MODIS_Band_Land, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0.0 to 1.0
  24. Mean_Reflectance_Land_All
      Description: Mean reflectance at 0.47, 0.66, and 2.1 µm after cloud screening
      Dimensions: (Solution_3_Land, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0.0 to 1.0
  25. Standard_Deviation_Reflectance_Land_All
      Description: Standard deviation of reflectance at 0.47, 0.66, and 2.1 µm after cloud screening
      Dimensions: (Solution_3_Land, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0.0 to 1.0
  26. Path_Radiance_Land
      Description: Path radiance at 0.47 and 0.66 µm
      Dimensions: (Solution_1_Land, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0.0 to 1.0
  27. Error_Path_Radiance_Land
      Description: Uncertainty of path radiance at 0.47 and 0.66 µm
      Dimensions: (Solution_1_Land, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0.0 to 1.0
  28. Critical_Reflectance_Land
      Description: Critical reflectance at 0.47 and 0.66 µm
      Dimensions: (Solution_1_Land, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0.0 to 1.0
  29. Error_Critical_Reflectance_Land
      Description: Uncertainty of critical reflectance at 0.47 and 0.66 µm
      Dimensions: (Solution_1_Land, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0.0 to 1.0
  30. QualityWeight_Path_Radiance_Land
      Description: Quality Flag for Path Radiance based on the test for fits
      Dimensions: (Solution_1_Land, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: -20.0 to 20.0
  31. QualityWeight_Critical_Reflectance_Land
      Description: Quality Flag forCritical_Reflectance based on the Test for fits
      Dimensions: (Solution_1_Land, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: -20.0 to 20.0
  32. STD_Reflectance_Land
      Description: Standard Deviation of reflectance at at 0.47, 0.55, 0.66, 0.87, 1.24, 1.64, and 2.13 µm
      Dimensions: (MODIS_Band_Land, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0 to 2



      Ocean Only

  33. Solution_Index_Ocean_Small
      Description: Solution number index (1 through 4) for small particles. Indices of ocean models 1 through 4 correspond to accumulation (small) mode models with effective radii 0.10, 0.15, 0.20, 0.25 µm, respectively.
      Dimensions: (Solution_Ocean, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 1 to 4
  34. Solution_Index_Ocean_Large
      Description: Solution number index (5 through 9) for large particles. Indices of ocean models 5 through 7 correspond to coarse (large) mode models of marine (sea salt) particles with effective radii 1.0, 1.5, 2.0 µm, respectively. Indices of ocean models 8 and 9 correspond to coarse (large) mode models of mineral dust particles with effective radii 1.5 and 2.5 µm, respectively.
      Dimensions: (Solution_Ocean, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 5 to 9
  35. Effective_Optical_Depth_Best_Ocean
      Description: Aerosol Optical Thickness for Best Solution at 7 bands 0.47, 0.55, 0.66, 0.86, 1.24, 1.63, and 2.13 µm
      Dimensions: (MODIS_Band_Ocean, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: -0.05 to 5.0
  36. Effective_Optical_Depth_Average_Ocean
      Description: Aerosol Optical Thickness for Average Solution at 7 bands 0.47, 0.55, 0.66, 0.86, 1.24, 1.63, and 2.13 µm
      Dimensions: (MODIS_Band_Ocean, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: -0.05 to 5.0
  37. Optical_Depth_Small_Best_Ocean
      Description: Aerosol Optical Thickness for Small Mode of Best Solution at 7 bands 0.47, 0.55, 0.66, 0.86, 1.24, 1.63, and 2.13 µm
      Dimensions: (MODIS_Band_Ocean, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: -0.05 to 5.0
  38. Optical_Depth_Small_Average_Ocean
      Description: Aerosol Optical Thickness for Small Mode of Average Solution at 7 bands 0.47, 0.55, 0.66, 0.86, 1.24, 1.63, and 2.13 µm
      Dimensions: (MODIS_Band_Ocean, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: -0.05 to 5.0
  39. Optical_Depth_Large_Best_Ocean
      Description: Aerosol Optical Thickness for Large Mode of Best Solution at 7 bands 0.47, 0.55, 0.66, 0.86, 1.24, 1.63, and 2.13 µm
      Dimensions: (MODIS_Band_Ocean, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: -0.05 to 5.0
  40. Optical_Depth_Large_Average_Ocean
      Description: Aerosol Optical Thickness at 7 bands 0.47, 0.55, 0.66, 0.86, 1.24, 1.63, and 2.13 µm for large mode of average solution
      Dimensions: (MODIS_Band_Ocean, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: -0.05 to 5.0
  41. Mass_Concentration_Ocean
      Description: Mass Concentration for Best and Average Solutions
      Dimensions: (Solution_Ocean, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0 to 1000 x 1.0e-6g/cm^2
  42. Effective_Radius_Ocean
      Description: Effective Radius of Both Solutions at 0.55 µm
      Dimensions: (Solution_Ocean, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0 to 5 µm
  43. Cloud_Condensation_Nuclei_Ocean
      Description: Column Number of CCN of Both Solutions at 0.55 µm
      Dimensions: (Solution_Ocean, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0.0 to 9.999E+10 CCN/cm^2
  44. Asymmetry_Factor_Best_Ocean
      Description: Asymmetry Factor for Best Solution at 7 bands 0.47, 0.55, 0.66, 0.86, 1.24, 1.63, and 2.13 µm
      Dimensions: (MODIS_Band_Ocean, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0 to 3
  45. Asymmetry_Factor_Average_Ocean
      Description: Asymmetry Factor for Average Solution at 7 bands 0.47, 0.55, 0.66, 0.86, 1.24, 1.63, and 2.13 µm
      Dimensions: (MODIS_Band_Ocean, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0 to 3
  46. Backscattering_Ratio_Best_Ocean
      Description: Backscattering Ratio of Best Solution at 7 bands 0.47, 0.55, 0.66, 0.86, 1.24, 1.63, and 2.13 µm
      Dimensions: (MODIS_Band_Ocean, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0 to 3
  47. Backscattering_Ratio_Average_Ocean
      Description: Backscattering Ratio of Average Solution at 7 bands 0.47, 0.55, 0.66, 0.86, 1.24, 1.63, and 2.13 µm
      Dimensions: (MODIS_Band_Ocean, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0 to 3
  48. Angstrom_Exponent_1_Ocean
      Description: Angstrom Exponent for 0.55 and 0.86 µm
      Dimensions: (Solution_Ocean, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: -1.0 to 5.0
  49. Angstrom_Exponent_2_Ocean
      Description: Angstrom Exponent for 0.865 and 2.130 µm
      Dimensions: (Solution_Ocean, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: -1.0 to 5.0
  50. Least_Squares_Error_Ocean
      Description: Least Square Error Estimate
      Dimensions: (Solution_Ocean, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0 to 1
  51. Optical_Depth_Ratio_Small_Ocean
      Description: Ratio of Optical Depth of Small Mode vs Effective Optical Depth at .55 µm for best (1) and average (2) solutions
      Dimensions: (Solution_Ocean, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0 to 1
  52. Optical_Depth_by_models_Ocean
      Description: Optical Depth for small and large modes placed in model index
      Dimensions: (Solution_Index, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0 to 1
  53. Cloud_Fraction_Ocean
      Description: Cloud fraction from Ocean aerosol cloud mask using retrieved and overcast pixels not including cirrus mask
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0.0 to 1.0
  54. Number_Pixels_Used_Ocean
      Description: Number of good pixels used for retrieval at at 865 nm
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 1 to 400
  55. Mean_Reflectance_Ocean
      Description: Mean Reflectances at 7 bands 0.47, 0.55, 0.66, 0.86, 1.24, 1.63, and 2.13 µm
      Dimensions: (MODIS_Band_Ocean, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0 to 1
  56. STD_Reflectance_Ocean
      Description: Standard Deviation of Reflectances at 7 bands 0.47, 0.55, 0.66, 0.86, 1.24, 1.63, and 2.13 µm
      Dimensions: (MODIS_Band_Ocean, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0 to 2



      Deep Blue Aerosol Only

  57. Deep_Blue_Aerosol_Optical_Depth_550_Land
      Description: Aerosol Optical Thickness at 0.55 micron for land (corrected) with all quality data (QA Confidence Flag = 1, 2, 3)
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0.0 to 5.0
  58. Deep_Blue_Aerosol_Optical_Depth_Land
      Description: Aerosol Optical Thickness at 0.412, 0.47, and 0.66 micron for land (corrected) with all quality data (QA Confidence Flag = 1, 2, 3)
      Dimensions: (Num_DeepBlue_Wavelengths, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0.0 to 5.0
  59. Deep_Blue_Angstrom_Exponent_Land
      Description: Deep Blue Angstrom Exponent for Land (0.412-0.47 micron) with all quality data (QA Confidence Flag = 1, 2, 3)
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: -0.5 to 5.0
  60. Deep_Blue_Single_Scattering_Albedo_Land
      Description: Deep Blue Single Scattering Albedo for Land at 0.412, 0.47, and 0.66 micron with all quality data (QA Confidence Flag = 1, 2, 3)
      Dimensions: (Num_DeepBlue_Wavelengths, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0.7 to 1.0
  61. Deep_Blue_Single_Surface_Reflectance_Land
      Description: Deep Blue Surface Reflectance for Land at 0.412, 0.47, and 0.66 micron with all quality data (QA Confidence Flag = 1, 2, 3)
      Dimensions: (Num_DeepBlue_Wavelengths, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0.0 to 1.0



    Cloud Mask and QA Parameters

  62. Cloud_Mask_QA
      Description: Cloud Mask QA at 10x10 km resolution
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: (bit mask; see QA Plan for details)
  63. Aerosol_Cldmask_Byproducts_Land
      Description: 3x3 pixels: Standard Deviation at 470 and 1380 nm; Reflectance at 555, 1380, and 2130 nm; Radiance at 11000 nm; Cirrus fraction
      Dimensions: (Num_By_Products, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0 to 1
  64. Quality_Assurance_Land
      Description: Run-Time QA Flags for Land
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath, QA_Byte_Land)
      Valid Range: (bit mask; see QA Plan for details)
  65. Quality_Assurance_Crit_Ref_Land
      Description: Run-Time QA Flags for Critical Reflectance over Land
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath, QA_Byte_Land)
      Valid Range: (bit mask)
  66. Quality_Assurance_Ocean
      Description: Run-Time QA Flags for Ocean
      Dimensions: (Cell_Along_Swath, Cell_Across_Swath, QA_Byte_Ocean)
      Valid Range: (bit mask; see QA Plan for details)
  67. Aerosol_Cldmask_Byproducts_Ocean
      Description: 3x3 pixels: Standard Deviation at 550 and 1380 nm; Reflectance at 550, 1380, and 2130 nm; Radiance at 11000 nm; Cirrus fraction
      Dimensions: (Num_By_Products, Cell_Along_Swath, Cell_Across_Swath)
      Valid Range: 0 to 1


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