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Format & Content

File Format Basics

MOD08_M3 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 739 gridded statistical fields within the HDF file is stored as a Scientific Data Set (SDS). Only a subset of statistics outlined in the Statistic List (see below) are computed for each parameter.


MOD08_M3 Parameter List

Parameters derived from MOD04_L2

AEROSOL: LAND & OCEAN (Y.KAUFMAN)
1. Scattering_Angle Derived from the MOD04_L2 SDS "Scattering_Angle".
2. Optical_Depth_Land_And_Ocean Derived from the MOD04_L2 SDS "Optical_Depth_Land_And_Ocean".
3. Optical_Depth_Ratio_Small_Land_And_Ocean Derived from the MOD04_L2 SDS "Optical_Depth_Ratio_Small_Land_And_Ocean".
4. Reflected_Flux_Land_And_Ocean Derived from the MOD04_L2 SDS "Reflected_Flux_Land_And_Ocean".

AEROSOL: LAND ONLY (Y.KAUFMAN)
5. Corrected_Optical_Depth_Land
Derived from the MOD04_L2 SDS "Corrected_Optical_Depth_Land". Note that this parameter group contains three joint histograms for optical depth computed using 0.47 vs 0.55 microns, 0.47 vs 0.66 microns, and 0.55 vs 0.66 microns at 5x5 intervals for each.
6. Optical_Depth_Ratio_Small_Land
Derived from the MOD04_L2 SDS "Optical_Depth_Ratio_Small_Land".
7. Mass_Concentration_Land Derived from the MOD04_L2 SDS "Mass_Concentration_Land".
8. Angstrom_Exponent_Land
Derived from the MOD04_L2 SDS "Angstrom_Exponent".
9. Transmitted_Flux_Land Derived from the MOD04_L2 SDS "Transmitted_Flux_Land".
10. Reflected_Flux_Land Derived from the MOD04_L2 SDS "Reflected_Flux_Land".
11. Mean_Reflectance_Land_All Derived from the MOD04_L2 SDS "Mean_Reflectance_Land_All". The parameter has three spectral band solutions (.47, .66, and 2.13 microns) Two groups of statistics are available in MOD08, one group is associated with QA for .47 microns, the other is associated with QA for .66 microns. The parameter groups are called Mean_Reflectance_Land_All_QA47 and Mean_Reflectance_Land_All_QA66, respectively.

AEROSOL: OCEAN ONLY (D.TANRE)
12. Mass_Concentration_Ocean Derived from the MOD04_L2 SDS "Mass_Concentration_Ocean ".
13. Effective_Optical_Depth_Average_Ocean Derived from the MOD04_L2 SDS "Effective_Optical_Depth_Average_Ocean".
14. Optical_Depth_Ratio_Small_860_Ocean Derived from the MOD04_L2 SDS "Optical_Depth_Ratio_Small_Ocean_0.86micron". There are two solutions (dimensions), one for best and one for average. (The now defunct parameter "Optical_Depth_Ratio_Small_Ocean" was derived at 0.55 and was replaced by this parameter in Spring 2002.)
15. Effective_Radius_Ocean Derived from the MOD04_L2 SDS "Effective_Radius_Ocean".
16. Cloud_Condensation_Nuclei_Ocean Derived from the MOD04_L2 SDS "Cloud_Condensation_Nuclei_Ocean".
17. Angstrom_Exponent_1_Ocean
18. Angstrom_Exponent_2_Ocean
Derived from the MOD04_L2 SDS "Angstrom_Exponent_1_Ocean" and "Angstrom_Exponent_2_Ocean", respectively.
19. Asymmetry_Factor_Average_Ocean Derived from the MOD04_L2 SDS "Asymmetry_Factor_Average_Ocean".
20. Backscattering_Ratio_Average_Ocean Derived from the MOD04_L2 SDS "Backscattering_Ratio_Average_Ocean".
21. Transmitted_Flux_Average_Ocean Derived from the MOD04_L2 SDS "Transmitted_Flux_Average_Ocean".
22. Reflected_Flux_Average_Ocean Derived from the MOD04_L2 SDS "Reflected_Flux_Average_Ocean".
23. Optical_Depth_by_models_ocean Derived from the MOD04_L2 SDS "Optical_Depth_by_models_ocean". The parameter has solutions at 9 models.

Parameters derived from MOD05_L2

WATER VAPOR (B.GAO)
24. Water_Vapor_Near_Infrared_Clear
25. Water_Vapor_Near_Infrared_Cloud
Derived from the MOD05_L2 SDS "Water_Vapor_Near_Infrared" and aggregated into a clear or cloud category from the MOD05_L2 SDS "Quality_Assurance_Near_Infrared".

Parameters derived from MOD06_L2

CIRRUS DETECTION (B.GAO)
26. Cirrus_Reflectance
27. Contrail_Reflectance
Derived from the MOD06_L2 SDS "Cirrus_Reflectance" and aggregated into a cirrus or contrail category from the MOD06_L2 SDS "Cirrus_Reflectance_Flag".
28. Cirrus_Fraction_SWIR
29. Contrail_Fraction_SWIR
Derived from the MOD06_L2 SDS "Cirrus_Reflectance_Flag" and aggregated into a cirrus or contrail category from the MOD06_L2 SDS "Cirrus_Reflectance_Flag". This flag differentiates between BadData, Non-Cirrus, Cirrus, or Contrail at 1km resolution.

CLOUD TOP PROPERITES (P.MENZEL)
30. Cloud_Top_Temperature
31. Cloud_Top_Temperature_Day
32. Cloud_Top_Temperature_Night
Derived from the MOD06_L2 SDS "Cloud_Top_Temperature" and aggregated into Day or Night categories from the MOD06_L2 SDS "Cloud_Mask_5km".
33. Cloud_Top_Pressure
34. Cloud_Top_Pressure_Day
35. Cloud_Top_Pressure_Night
Derived from the MOD06_L2 SDS "Cloud_Top_Pressure" and aggregated into Day or Night categories from the MOD06_L2 SDS "Cloud_Mask_5km".
36. Cloud_Effective_Emissivity
37. Cloud_Effective_Emissivity_Day
38. Cloud_Effective_Emissivity_Night
Derived from the MOD06_L2 SDS "Cloud_Effective_Emissivity" and aggregated into Day or Night categories from the MOD06_L2 SDS "Cloud_Mask_5km".
39. Cloud_Phase_Infrared
40. Cloud_Phase_Infrared_Day
41. Cloud_Phase_Infrared_Night
Derived from the MOD06_L2 SDS "Cloud_Phase_Infrared" and aggregated into Day or Night categories from the MOD06_L2 SDS "Cloud_Mask_5km". The various dimensions of the Histogram Counts statistic corresponds to clear = 0, water = 1 or 5, ice = 2 or 4, mixed = 3, and uncertain = 6. Note that categories 4 and 5 were eliminated in a year 2000 L2 code delivery.
42. Cloud_Fraction_Infrared
43. Cloud_Fraction_Infrared_Day
44. Cloud_Fraction_Infrared_Night
Derived from the MOD06_L2 SDS "Cloud_Fraction" and aggregated into Day or Night categories from the MOD06_L2 SDS "Cloud_Mask_5km".
45. Cirrus_Fraction_Infrared
46. High_Cloud_Fraction_Infrared
Derived from the MOD06_L2 SDS "Quality_Assurance_5km" The SDS's are an interpretation of the Retrieval Processing Path Flags: Cirrus/NoCirrus or HighCloud/NoHighCloud.

CLOUD OPTICAL PROPERTIES (M.KING)
47. Cloud_Optical_Thickness_Water
48. Cloud_Optical_Thickness_Ice
49. Cloud_Optical_Thickness_Undetermined
50. Cloud_Optical_Thickness_Mixed_Phase
51. Cloud_Optical_Thickness_Combined
Derived from the MOD06_L2 SDS "Cloud_Optical_Thickness" and aggregated into Cloud Phase categories (water, ice, undetermined, mixed, combined) from the MOD06_L2 SDS "Quality_Assurance_1km". Note that the liquid water cloud parameter contains three joint histograms for COT vs Cloud Effective Radius, COT vs Cloud Top Temperature, and COT vs Effective Emissivity at 11x10, 11x12, and 11x10 intervals, respectively; and the ice cloud parameter also contains the same three joint histograms but at 11x12, 11x10, and 11x10 intervals, respectively.
52. Cloud_Effective_Radius_Water
53. Cloud_Effective_Radius_Ice
54. Cloud_Effective_Radius_Undetermined
55. Cloud_Effective_Radius_Mixed_Phase
56. Cloud_Effective_Radius_Combined
Derived from the MOD06_L2 SDS "Effective_Particle_Radius" and aggregated into Cloud Phase categories (water, ice, undetermined, mixed, combined) from the MOD06_L2 SDS "Quality_Assurance_1km". Note that the liquid water cloud parameter contains two joint histograms for CER vs Cloud Top Temperature and CER vs Effective Emissivity at 10x12 and 10x10 intervals, respectively; and the ice cloud parameter also contains the same two joint histograms but at 12x10 and 12x10 intervals, respectively.
57. Water_Path_Liquid
58. Water_Path_Ice
59. Water_Path_Undetermined
60. Water_Path_Mixed_Phase
61. Water_Path_Combined
Derived from the MOD06_L2 SDS "Water_Path" and aggregated into Cloud Phase categories (water, ice, undetermined, mixed, combined) from the MOD06_L2 SDS "Quality_Assurance_1km".
62. Cloud_Fraction_Water
63. Cloud_Fraction_Ice
64. Cloud_Fraction_Undetermined
65. Cloud_Fraction_Mixed_Phase
66. Cloud_Fraction_Total
Derived (and aggregated into Cloud Phase categories: water, ice, undetermined, mixed, combined) from the MOD06_L2 SDS "Quality_Assurance_1km". The SDS's are an interpretation of the Retrieval Processing Path Flags (decision tree outcome) that is determined from the Cloud Mask, IR and SWIR tests.
67. Cloud_Fraction_SWIR_Water
68. Cloud_Fraction_SWIR_Ice
69. Cloud_Fraction_SWIR_Undetermined
70. Cloud_Fraction_SWIR_Total
Derived (and aggregated into Cloud Phase categories: water, ice, undetermined, combined) from the MOD06_L2 SDS "Quality_Assurance_1km". The SDS's are an interpretation of the Determination of Cloud Phase from the SWIR test only. Note that as of March 2001, the SWIR algorithm is still under development, so these SDS parameters contain all missing data.

Parameters derived from MOD07_L2

ATMOSPHERE PROFILE (P.MENZEL)
71. Total_Ozone Derived from the MOD07_L2 SDS "Total_Ozone".
72. Total_Totals Derived from the MOD07_L2 SDS "Total_Totals".
73. Lifted_Index Derived from the MOD07_L2 SDS "Lifted_Index".
74. K_Index Derived from the MOD07_L2 SDS "K_Index".
75. Atmospheric_Water_Vapor
76. Atmospheric_Water_Vapor_Low
77. Atmospheric_Water_Vapor_High
Derived from the MOD07_L2 SDS's "Water_Vapor, "Water_Vapor_Low", and "Water_Vapor_High", respectively. The keywords "Low" and "High" refer to the lower and higher portions of the atmospheric column. Note that the parameter "Water Vapor" is also refered to as "Precipitable Water".





MOD08_M3 Statistic List

A number of statistical summaries are computed, depending on the science parameter being considered. Statistics for a given Level-2 measurement might include:

    Simple Statistics of the Mean

  1. Mean_Mean
  2. Mean_Min
  3. Mean_Max
  4. Mean_Std

    Mean of the Standard Deviation

  5. Std_Deviation_Mean

    QA Weighted Statistics

  6. QA_Mean_Mean
  7. QA_Mean_Std
  8. QA_Mean_Min
  9. QA_Mean_Max
  10. QA_Std_Deviation_Mean

    Histograms of the quantity within each grid box

  11. Histogram_Counts

    Histograms of the confidence placed in each measurement

  12. Confidence_Histograms

    Mean and Standard Deviation of the Fraction of pixels that satisfy some condition (e.g. cloudy, clear)

  13. FMean
  14. FStd

    Total number of observations (pixels) within each grid box

  15. Pixel_Counts

    Parameters of Log-Normal Distributions

  16. Log_Mean_Mean
  17. Log_Mean_Std
  18. Log_Mean_Min
  19. Log_Mean_Max
  20. Log_Std_Deviation_Mean

    Parameters of QA Weighted Log-Normal Distributions

  21. QA_Log_Mean_Mean
  22. QA_Log_Mean_Std
  23. QA_Log_Mean_Min
  24. QA_Log_Mean_Max
  25. QA_Log_Std_Deviation_Mean

    Regressions and/or Histograms derived from comparing one science parameter to another, statistics may be computed for a subset that satisfies some condition

  26. Regression_Slope
  27. Regression_Intercept
  28. Regression_R_Squared
  29. Regression_Mean_Square_Error
  30. Joint_Histogram_vs_Effect_Radius
  31. Joint_Histogram_vs_Temperature
  32. Joint_Histogram_vs_Emissivity
  33. Joint_Histogram_47vs55
  34. Joint_Histogram_47vs66
  35. Joint_Histogram_55vs66


Statistic Computation Details

Below are more details on the computation of each statistic:

For the daily product, assume that x1, x2, , xn represent the retrieved pixel values of a Level-2 parameter over a 1 x 1 degree grid box, Qi is the quality flag for each retrieved pixel value, and wi is the weighting factor (1 for the daily case), then the simple statistics are defined as:

In these equations, (1) will be referred to as the 'regular' mean, (2) as the QA weighted mean, (3) as the regular standard deviation, (4) as the QA weighted standard deviation, (5) as the minimum, and (6) as the maximum.

The simple statistics also include daily log regular mean, log standard deviation, log QA mean, and log QA standard deviation. These log quantities are calculated as shown in equations (1 - 4), except that x1, x2, , xn are replaced by their logarithms.

Regression statistics, based on the pixels within each 1 by 1 degree grid cell, includes the slope, intercept, mean-squared-error (MSE), and the coefficient of determination (R2).

The histograms and joint histograms report the counts of the pixels falling into predetermined numerical intervals.

The pixel counts are used to represent the number of pixels for the parameters which do not have QA flags, while the confidence-histograms-counts are used to represent the number of counts for each parameter that falls within each QA bin (e.g., questionable, good, very good, and total).