MODIS Atmosphere
MODIS Atmosphere Home Products  Images  Validation  News  Staff  Forum  Reference  Tools  Help
Aerosol Product  Water Vapor Product  Cloud Product  Atmosphere Profile Product  Cloud Mask Product   Joint Atmosphere ProductLevel-2 Products
Daily Global Product  Eight-Day Global Product  Monthly Global ProductLevel-3 Products       Filled Land Surface Albedo ProductFilled Normalized Difference Vegetative Index ProductOne-Minute Land Ecosystem Classification ProductLevel-3 Ancillary Land Surface Products
MOD35_L2
Introduction
Format and Content
Grids & Mapping
Sample Images
QA Information
Modification History
Acquiring Data
Filename Convention
Analysis Tools
Theoretical Basis
Validation
Detailed File Spec
Algorithm Software
Production Plan
Support Team

Format and Content

File Format Basics

MOD35_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 9 gridded parameters listed below is stored as a Scientific Data Set (SDS) within the HDF file.

The Cloud Mask and Quality Assurance SDS's are stored at 1 kilometer pixel resolution. All other SDS's (those relating to time, geolocation, and viewing geometry) are stored at 5 kilometer pixel resolution.




MOD35_L2 Dimension List

  1. Cell_Along_Swath_5km = 406 (typical)
  2. Cell_Across_Swath_5km = 270 (typical)
  3. Cell_Along_Swath_1km = 2030 (typical)
  4. Cell_Across_Swath_1km = 1354 (typical)
  5. Byte_Segment = 6 (array values are 1 to 6 in sequence)
  6. QA_Dimension = 10
  7. Number_of_Instrument_Scans = 203 (typical)
  8. Maximum_Number_of_1km_Frames = 1354 (typical)



MOD35_L2 Scientific Data Set (SDS) List

    Geolocation and Time Parameters

  1. Latitude
      Description: Geodetic Latitude
      Dimensions: (Cell_Along_Swath_5km, Cell_Across_Swath_5km)
      Valid Range: -90 to +90 degrees north
  2. Longitude
      Description: Geodetic Longitude
      Dimensions: (Cell_Along_Swath_5km, Cell_Across_Swath_5km)
      Valid Range: -180 to +180 degrees east
  3. 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

  4. Solar_Zenith
      Description: Solar Zenith Angle, Cell to Sun
      Dimensions: (Cell_Along_Swath_5km, Cell_Across_Swath_5km)
      Valid Range: 0 to +180 degrees
  5. Solar_Azimuth
      Description: Solar Azimuth Angle, Cell to Sun
      Dimensions: (Cell_Along_Swath_5km, Cell_Across_Swath_5km)
      Valid Range: -180 to +180 degrees
  6. Sensor_Zenith
      Description: Sensor Zenith Angle, Cell to Sensor
      Dimensions: (Cell_Along_Swath_5km, Cell_Across_Swath_5km)
      Valid Range: 0 to 180 degrees
  7. 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

      Cloud Mask (1km)

  8. Cloud_Mask
      Description: MODIS Cloud Mask and Spectral Test Results
      Dimensions: (Byte_Segment, Cell_Along_Swath_1km, Cell_Across_Swath_1km)
      Valid Range: bit field

      Quality Assurance (1km)

  9. Quality_Assurance
      Description: Quality Assurance for Cloud Mask
      Dimensions: (Cell_Along_Swath_1km, Cell_Across_Swath_1km, QA_Dimension)
      Valid Range: bit field




Cloud_Mask Bit-Field Interpretation

Each pixel in the Cloud_Mask SDS is assigned a 6 byte (48 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.

Cloud_Mask Bit-Field Interpretation
Byte #0
(1km Cloud Mask & Processing Path Flags)
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
Byte #1
(Additional 1km Flags)
Bits Field Description Bit Interpretation Key
0 Non-Cloud Obstruction Flag 0 = Yes
1 = No
1 Thin Cirrus Detected (Solar Test) 0 = Yes
1 = No
2 Shadow Flag 0 = Yes
1 = No
3 Thin Cirrus Detected (Infrared Test) 0 = Yes
1 = No
4 Adjacent Cloud Detected
(within surrounding 1 km pixels) 		0 = Yes
1 = No
5 Cloud Flag (IR Threshold Test) 0 = Yes
1 = No
6 High Cloud Flag (CO2 Test) 0 = Yes
1 = No
7 High Cloud Flag (6.7 micron Test) 0 = Yes
1 = No
Byte #2
(Additional 1km Flags)
Bits Field Description Bit Interpretation Key
0 High Cloud Flag (1.38 micron Test) 0 = Yes
1 = No
1 High Cloud Flag (3.7-12 micron Test) 0 = Yes
1 = No
2 Cloud Flag (IR Temperature Difference Test) 0 = Yes
1 = No
3 Cloud Flag (3.7-11 micron Test) 0 = Yes
1 = No
4 Cloud Flag (Visible Reflectance Test) 0 = Yes
1 = No
5 Cloud Flag (Visible Reflectance Ratio Test) 0 = Yes
1 = No
6 Cloud Flag (.935/.87 Reflectance Test) 0 = Yes
1 = No
7 Cloud Flag (3.7-3.9 micron Test) 0 = Yes
1 = No
Byte #3
(Additional 1km Flags)
Bits Field Description Bit Interpretation Key
0 Cloud Flag (Temporal Consistency) 0 = Yes
1 = No
1 Cloud Flag (Spatial Variability) 0 = Yes
1 = No
2-7 (spares) n/a
Byte #4
(250m Flags)
Bits Field Description Bit Interpretation Key
0 250-m Cloud Flag (Visible Test)
element(1,1) 		0 = Yes
1 = No
1 250-m Cloud Flag (Visible Test)
element(1,2) 		0 = Yes
1 = No
2 250-m Cloud Flag (Visible Test)
element(1,3) 		0 = Yes
1 = No
3 250-m Cloud Flag (Visible Test)
element(1,4) 		0 = Yes
1 = No
4 250-m Cloud Flag (Visible Test)
element(2,1) 		0 = Yes
1 = No
5 250-m Cloud Flag (Visible Test)
element(2,2) 		0 = Yes
1 = No
6 250-m Cloud Flag (Visible Test)
element(2,3) 		0 = Yes
1 = No
7 250-m Cloud Flag (Visible Test)
element(2,4) 		0 = Yes
1 = No
Byte #5
(250m Flags)
Bits Field Description Bit Interpretation Key
0 250-m Cloud Flag (Visible Test)
element(3,1) 		0 = Yes
1 = No
1 250-m Cloud Flag (Visible Test)
element(3,2) 		0 = Yes
1 = No
2 250-m Cloud Flag (Visible Test)
element(3,3) 		0 = Yes
1 = No
3 250-m Cloud Flag (Visible Test)
element(3,4) 		0 = Yes
1 = No
4 250-m Cloud Flag (Visible Test)
element(4,1) 		0 = Yes
1 = No
5 250-m Cloud Flag (Visible Test)
element(4,2) 		0 = Yes
1 = No
6 250-m Cloud Flag (Visible Test)
element(4,3) 		0 = Yes
1 = No
7 250-m Cloud Flag (Visible Test)
element(4,4) 		0 = Yes
1 = No




Quality_Assurance Bit-Field Interpretation

Each pixel in the Quality_Assurance SDS is assigned a 10 byte (80 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.

Quality_Assurance Bit-Field Interpretation
Byte #0
(1km Product Run-Time QA Flags)
Bits Field Description Bit Interpretation Key
0 Cloud Mask QA (1km) 0 = Not Useful
1 = Useful
1-3 Cloud Mask Confidence QA (1km) 0 = Lowest Confidence
1 = (not used)
2 = (not used)
3 = (not used)
4 = Intermediate Confidence
5 = (not used)
6 = High Confidence
7 = Highest Confidence
4-7 (spares) n/a
Byte #1
(1km Test Application Flags)
Bits Field Description Bit Interpretation Key
0 NCO Test 0 = Not Applied
1 = Applied
1 Thin Cirrus Test (Solar) 0 = Not Applied
1 = Applied
2 Shadow Test 0 = Not Applied
1 = Applied
3 Thin Cirrus Test (IR) 0 = Not Applied
1 = Applied
4 Cloud Adjancency Test (IR) 0 = Not Applied
1 = Applied
5 IR Threshold Test 0 = Not Applied
1 = Applied
6 High Cloud Test (CO2) 0 = Not Applied
1 = Applied
7 High Cloud Test (6.7) 0 = Not Applied
1 = Applied
Byte #2
(1km Test Application Flags)
Bits Field Description Bit Interpretation Key
0 High Cloud Test (1.38 microns) 0 = Not Applied
1 = Applied
1 High Cloud Test (3.7-12 microns) 0 = Not Applied
1 = Applied
2 IR Temperature Difference Tests 0 = Not Applied
1 = Applied
3 3.7-11 micron Test 0 = Not Applied
1 = Applied
4 .68 Reflectance Test 0 = Not Applied
1 = Applied
5 Visible Ratio Test 0 = Not Applied
1 = Applied
6 Near IR Reflectance Ratio Test 0 = Not Applied
1 = Applied
7 3.7-3.9 micron Test 0 = Not Applied
1 = Applied
Byte #3
(1km Test Application Flags)
Bits Field Description Bit Interpretation Key
0 Temporal Consistency Test 0 = Not Applied
1 = Applied
1 Spatial Variability Test 0 = Not Applied
1 = Applied
2-7 (spares) n/a
Byte #4
(250m Test Application Flags)
Bits Field Description Bit Interpretation Key
0 250 m Visible Test
element(1,1) 		0 = Not Applied
1 = Applied
1 250 m Visible Test
element(1,2) 		0 = Not Applied
1 = Applied
2 250 m Visible Test
element(1,3) 		0 = Not Applied
1 = Applied
3 250 m Visible Test
element(1,4) 		0 = Not Applied
1 = Applied
4 250 m Visible Test
element(2,1) 		0 = Not Applied
1 = Applied
5 250 m Visible Test
element(2,2) 		0 = Not Applied
1 = Applied
6 250 m Visible Test
element(2,3) 		0 = Not Applied
1 = Applied
7 250 m Visible Test
element(2,4) 		0 = Not Applied
1 = Applied
Byte #5
(250m Test Application Flags)
Bits Field Description Bit Interpretation Key
0 250 m Visible Test
element(3,1) 		0 = Not Applied
1 = Applied
1 250 m Visible Test
element(3,2) 		0 = Not Applied
1 = Applied
2 250 m Visible Test
element(3,3) 		0 = Not Applied
1 = Applied
3 250 m Visible Test
element(3,4) 		0 = Not Applied
1 = Applied
4 250 m Visible Test
element(4,1) 		0 = Not Applied
1 = Applied
5 250 m Visible Test
element(4,2) 		0 = Not Applied
1 = Applied
6 250 m Visible Test
element(4,3) 		0 = Not Applied
1 = Applied
7 250 m Visible Test
element(4,4) 		0 = Not Applied
1 = Applied
Byte #6
(1km Data Information Flags)
Bits Field Description Bit Interpretation Key
0-1 Number of Bands used to generate Cloud Mask 0 = None
1 = 1 to 7
2 = 8 to 14
3 = 15 to 21
2-3 Number of Spectral Tests used to generate Cloud Mask 0 = None
1 = 1 to 3
2 = 4 to 6
3 = 7 to 9
4-7 (spares) n/a
Byte #7
(1km Data Resource Flags)
Bits Field Description Bit Interpretation Key
0-1 Clear Radiance Origin 0 = MOD35
1 = Model forward calculation
2 = Other
3 = Not used
2-3 Surface Temperature over Land 0 = NCEP GDAS
1 = DAO
2 = MOD11
3 = Other
4-5 Surface Temperature over Ocean 0 = Reynolds blended
1 = DAO
2 = MOD28
3 = Other
6-7 Surface Winds 0 = NCEP GDAS
1 = DAO
2 = Other
3 = Not used
Byte #8 (1km Data Resource Flags)
Bits Field Description Bit Interpretation Key
0-1 Ecosystem Map 0 = Loveland N.A. 1km
1 = Olson Ecosystem
2 = MOD12
3 = Other
2-3 Snow Mask 0 = MOD33
1 = SSM/I Product
2 = Other
3 = Not used
4-5 Ice Cover 0 = MOD42
1 = SSM/I Product
2 = Other
3 = Not used
6-7 Land/Sea Mask 0 = USGS 1km 6-level
1 = USGS 1km binary
2 = Other
3 = Not Used
Byte #9 (1km Data Resource Flags)
Bits Field Description Bit Interpretation Key
0 Digital Elevation Model 0 = EOS DEM
1 = Not used
1-2 Precipitable Water 0 = NCEP GDAS
1 = DAO
2 = MOD07
3 = Other
3-7 (spares) n/a



Next Page
GRIDS