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File Format Basics
MOD05_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 13 gridded parameters listed below
is stored as a Scientific Data Set (SDS) within the HDF file.
The Water Vapor and Quality Assurance SDS's are stored at both 1 and 5 kilometer pixel resolution.
All other SDS's (those relating to time, geolocation, and viewing geometry)
are stored only at 5 kilometer pixel resolution. The Cloud Mask SDS, copied from the
MOD35_L2 Product is stored at 1 kilometer resolution.
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MOD05_L2 Dimension List
- Cell_Along_Swath_5km = 406 (typical)
- Cell_Across_Swath_5km = 270 (typical)
- Cell_Along_Swath_1km = 2030 (typical)
- Cell_Across_Swath_1km = 1354 (typical)
- QA_Byte_NIR = 1
- QA_Byte_IR = 5
- Number_of_Instrument_Scans = 203 (typical)
- Maximum_Number_of_1km_Frames = 1354 (typical)
MOD05_L2 Scientific Data Set (SDS) List
Geolocation and Time Parameters
- Latitude
Description: Geodetic Latitude
Dimensions: (Cell_Along_Swath_5km, Cell_Across_Swath_5km)
Valid Range: -90 to +90 degrees north
- Longitude
Description: Geodetic Longitude
Dimensions: (Cell_Along_Swath_5km, Cell_Across_Swath_5km)
Valid Range: -180 to +180 degrees east
- Scan_Start_Time
Description: International Atomic Time at Start of Scan
replicated across the Swath
Dimensions: (Cell_Along_Swath_5km, Cell_Across_Swath_5km)
Valid Range: 0.0 to 3.1558E+9 seconds since 1 January 1993 00:00:00
Solar and Viewing Geometry Parameters
- Solar_Zenith
Description: Solar Zenith Angle, Cell to Sun
Dimensions: (Cell_Along_Swath_5km, Cell_Across_Swath_5km)
Valid Range: 0 to +180 degrees
- Solar_Azimuth
Description: Solar Azimuth Angle, Cell to Sun
Dimensions: (Cell_Along_Swath_5km, Cell_Across_Swath_5km)
Valid Range: -180 to +180 degrees
- Sensor_Zenith
Description: Sensor Zenith Angle, Cell to Sensor
Dimensions: (Cell_Along_Swath_5km, Cell_Across_Swath_5km)
Valid Range: 0 to 180 degrees
- Sensor_Azimuth
Description: Sensor Azimuth Angle, Cell to Sensor
Dimensions: (Cell_Along_Swath_5km, Cell_Across_Swath_5km)
Valid Range: -180 to 180 degrees
Science Parameters
- Water_Vapor_Near_Infrared
Description: Total Column Precipitable Water Vapor - Near Infrared Retrieval
Dimensions: (Cell_Along_Swath_1km, Cell_Across_Swath_1km)
Valid Range: 0 to 20 cm
- Water_Vapor_Infrared
Description: Total Column Precipitable Water Vapor - IR Retrieval
Dimensions: (Cell_Along_Swath_5km, Cell_Across_Swath_5km)
Valid Range: 0 to 20 cm
- Water_Vapor_Correction_Factors
Description: Water Vapor Retrieval Algorithm Correction Factors
Dimensions: (Cell_Along_Swath_1km, Cell_Across_Swath_1km)
Valid Range: (byte array)
- Quality_Assurance_Near_Infrared
Description: Runtime Quality Assurance flags for Water_Vapor_Near_Infrared
Dimensions: (Cell_Along_Swath_1km, Cell_Across_Swath_1km, QA_Byte_NIR)
Valid Range: bit field (see MODIS Atmosphere QA Plan for details)
- Quality_Assurance_Infrared
Description: Runtime Quality Assurance flags for Water_Vapor_Infrared
Dimensions: (Cell_Along_Swath_5km, Cell_Across_Swath_5km, QA_Byte_IR)
Valid Range: bit field
- Cloud_Mask
Description: MODIS Cloud Mask , First Byte
Dimensions: (Cell_Along_Swath_1km, Cell_Across_Swath_1km)
Valid Range: bit field
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Cloud_Mask Bit-Field Interpretation
The Cloud_Mask SDS is copied from a portion of the complete MODIS Cloud Mask
SDS in the MOD35_L2 Product.
Each pixel in the Cloud_Mask SDS is assigned a 1 byte (8 bit) array.
Individual bits or groups of bits are set to
denote various cloud conditions and characteristics for that pixel.
All bit and byte numbering, in the table below, will start with 0.
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Cloud_Mask Bit-Field Interpretation
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Byte #0
(1km Cloud Mask & Processing Path Flags)
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| Bits |
Field Description |
Bit Interpretation Key |
| 0 |
Cloud Mask Flag |
0 = Not Determined
1 = Determined |
| 1-2 |
Unobstructed FOV Quality Flag |
0 = Confident Cloudy
1 = Probably Cloudy
2 = Probably Clear
3 = Confident Clear |
| 3 |
Day/Night Flag |
0 = Night
1 = Day |
| 4 |
Sunglint Flag |
0 = Yes
1 = No |
| 5 |
Snow/Ice Background Flag |
0 = Yes
1 = No |
| 6-7 |
Land/Water Background Flag |
0=Water
1=Coastal
2=Desert
3=Land |
Quality_Assurance_Infrared Bit-Field Interpretation
Each pixel in the Quality_Assurance_Infrared SDS is assigned a 5 byte (40 bit) array.
Individual bits or groups of bits are set to
denote various quality run-time characteristics for that pixel.
All bit and byte numbering, in the table below, will start with 0.
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Quality_Assurance_Infrared Bit-Field Interpretation
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Byte #0
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| Bits |
Field Description |
Bit Interpretation Key |
| 0 |
IR Water Vapor QA |
0 = Not Useful
1 = Useful |
| 1-3 |
IR Water Vapor Confidence QA (1km) |
0 = Lowest Confidence
1 = Intermediate Confidence
2 = High Confidence
3 = Highest Confidence
4-7 = Not Used |
| 4-7 |
(spares) |
n/a |
Byte #1
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| Bits |
Field Description |
Bit Interpretation Key |
| 0-7 |
Number of Cloudy Pixels within 5x5 km box |
valid range: 0 to 25 |
Byte #2
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| Bits |
Field Description |
Bit Interpretation Key |
| 0-7 |
Number of Clear Pixels within 5x5 km box |
valid range: 0 to 25 |
Byte #3
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| Bits |
Field Description |
Bit Interpretation Key |
| 0-7 |
Number of Missing Pixels within 5x5 km box |
valid range: 0 to 25 |
Byte #4
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| Bits |
Field Description |
Bit Interpretation Key |
| 0-1 |
IR Water Vapor Retrieval Method Used |
0 = Split Window (11-12)
1 = Moisture Profile Integration
2 = Other
3 = No Retrieval |
| 2-7 |
(spares) |
n/a |
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