Data Fields - SMAP L2 Radar Half-Orbit 3 km EASE-Grid Soil Moisture, Version 3

This page provides a description of all data fields within the SMAP L2 Radar Half-Orbit 3 km EASE-Grid Soil Moisture (SPL2SMA) product. The data are grouped into four main HDF5 groups:

For a description of metadata fields for this product, refer to the Metadata Fields document.
 

Ancillary_Data [top]

Table 1 describes the data fields of a typical SPL2SMA descending half-orbit granule. All data element arrays are one-dimensional with a size N, where N is the number of valid cells from the radar swath that appear on the grid.

Table 1. Data FIelds for Ancillary_Data
Data Field Name Shape Concept Byte Signed Unit Min Max Fill/Gap Value
bare_soil_roughness_tabular EASEGridCell_Array real 4 N/A meters 0.0 0.04 -9999.0
faraday_rotation_angle EASEGridCell_Array real 4 N/A degrees -999999.9 999999.9 -9999.0
landcover_class EASEGridCell_Array enum 1 N/A N/A N/A N/A 254
normalized_difference_vegetation_index EASEGridCell_Array real 4 N/A N/A -999999.9 999999.9 -9999.0
static_water_body_fraction EASEGridCell_Array real 4 N/A N/A 0.0 1.0 -9999.0
surface_temperature EASEGridCell_Array real 4 N/A degrees Celsius -50.0 60.0 -9999.0
vegetation_water_content_NDVI EASEGridCell_Array real 4 N/A kg/m**3 0.0 10.0 -9999.0
vegetation_water_content_RVI EASEGridCell_Array real 4 N/A kg/m**3 0.0 10.0 -9999.0

Metadata [top]

For a description of metadata fields for this product, refer to the Metadata Fields document.

Radar_Data [top]

Table 2 describes the data fields of a typical SPL2SMA descending half-orbit granule. All data element arrays are one-dimensional with a size N, where N is the number of valid cells from the radar swath that appear on the grid.

Table 2. Data Fields for Radar_Data
Data Field Name Shape Concept Byte Signed Unit Min Max Fill/Gap Value
altitude_std_dev EASEGridCell_Array real 4 N/A meters 0.0 1000.0 -9999.0
cell_radar_mode_flag EASEGridCell_Array bit flag 2 N/A N/A N/A N/A 65534
earth_boresight_azimuth_aft EASEGridCell_Array real 4 N/A degrees 0.0 360.0 -9999.0
earth_boresight_azimuth_fore EASEGridCell_Array real 4 N/A degrees 0.0 360.0 -9999.0
kp_hh EASEGridCell_Array real 4 N/A normalized 0.0 1.0 -9999.0
kp_hh_aft EASEGridCell_Array real 4 N/A normalized 0.0 1.0 -9999.0
kp_hh_fore EASEGridCell_Array real 4 N/A normalized 0.0 1.0 -9999.0
kp_vv EASEGridCell_Array real 4 N/A normalized 0.0 1.0 -9999.0
kp_vv_aft EASEGridCell_Array real 4 N/A normalized 0.0 1.0 -9999.0
kp_vv_fore EASEGridCell_Array real 4 N/A normalized 0.0 1.0 -9999.0
kp_xpol EASEGridCell_Array real 4 N/A normalized 0.0 1.0 -9999.0
kp_xpol_aft EASEGridCell_Array real 4 N/A normalized 0.0 1.0 -9999.0
kp_xpol_fore EASEGridCell_Array real 4 N/A normalized 0.0 1.0 -9999.0
sigma0_hh_mean EASEGridCell_Array real 4 N/A normalized -0.01 10.0 -9999.0
sigma0_hh_mean_aft EASEGridCell_Array real 4 N/A normalized -0.01 10.0 -9999.0
sigma0_hh_mean_fore EASEGridCell_Array real 4 N/A normalized -0.01 10.0 -9999.0
sigma0_hh_std_dev EASEGridCell_Array real 4 N/A normalized 0.0 5.0 -9999.0
sigma0_hh_std_dev_aft EASEGridCell_Array real 4 N/A normalized 0.0 5.0 -9999.0
sigma0_hh_std_dev_fore EASEGridCell_Array real 4 N/A normalized 0.0 5.0 -9999.0
sigma0_vv_mean EASEGridCell_Array real 4 N/A normalized -0.01 10.0 -9999.0
sigma0_vv_mean_aft EASEGridCell_Array real 4 N/A normalized -0.01 10.0 -9999.0
sigma0_vv_mean_fore EASEGridCell_Array real 4 N/A normalized -0.01 10.0 -9999.0
sigma0_vv_std_dev EASEGridCell_Array real 4 N/A normalized 0.0 5.0 -9999.0
sigma0_vv_std_dev_aft EASEGridCell_Array real 4 N/A normalized 0.0 5.0 -9999.0
sigma0_vv_std_dev_fore EASEGridCell_Array real 4 N/A normalized 0.0 5.0 -9999.0
sigma0_xpol_mean EASEGridCell_Array real 4 N/A normalized -0.01 10.0 -9999.0
sigma0_xpol_mean_aft EASEGridCell_Array real 4 N/A normalized -0.01 10.0 -9999.0
sigma0_xpol_mean_fore EASEGridCell_Array real 4 N/A normalized -0.01 10.0 -9999.0
sigma0_xpol_std_dev EASEGridCell_Array real 4 N/A normalized 0.0 5.0 -9999.0
sigma0_xpol_std_dev_aft EASEGridCell_Array real 4 N/A normalized 0.0 5.0 -9999.0
sigma0_xpol_std_dev_fore EASEGridCell_Array real 4 N/A normalized 0.0 5.0 -9999.0

Soil_Moisture_Retrieval_Data [top]

Table 3 describes the data fields of a typical SPL2SMA descending half-orbit granule. All data element arrays are one-dimensional with a size N, where N is the number of valid cells from the radar swath that appear on the grid.

Table 3. Data Fields for Soil_Moisture_Retrieval_Data
Data Field Name Shape Concept Byte Signed Unit Min Max Fill/Gap Value
EASE_column_index EASEGridCell_Array integer 2 false count 0 65535 65534
EASE_row_index EASEGridCell_Array integer 2 false count 0 65535 65534
bare_soil_roughness_retrieved EASEGridCell_Array real 4 N/A meters 0.0 0.1 -9999.0
distance_from_nadir EASEGridCell_Array real 4 N/A meters 0.0 500000.0 -9999.0
latitude EASEGridCell_Array real 4 N/A degrees_north -90.0 90.0 N/A
longitude EASEGridCell_Array real 4 N/A degrees_east -180.0 180.0 N/A
num_input_sigma0s_hh EASEGridCell_Array integer 2 false count 0 100 65534
num_input_sigma0s_vv EASEGridCell_Array integer 2 false count 0 100 65534
num_input_sigma0s_xpol EASEGridCell_Array integer 2 false count 0 100 65534
num_time_series EASEGridCell_Array integer 1 false count 0 255 254
radar_vegetation_index EASEGridCell_Array real 4 N/A count 0.0 2.0 -9999.0
radar_water_flag3 EASEGridCell_Array integer 1 false count 0 255 254
retrieval_qual_flag EASEGridCell_Array bit flag 2 N/A N/A N/A N/A 65534
retrieval_qual_flag_change_index EASEGridCell_Array bit flag 2 N/A N/A N/A N/A 65534
retrieval_qual_flag_cube EASEGridCell_Array bit flag 2 N/A N/A N/A N/A 65534
retrieval_qual_flag_kvz EASEGridCell_Array bit flag 2 N/A N/A N/A N/A 65534
sigma0_qual_flag_hh EASEGridCell_Array bit flag 4 N/A N/A N/A N/A 4294967294
sigma0_qual_flag_vv EASEGridCell_Array bit flag 4 N/A N/A N/A N/A 4294967294
sigma0_qual_flag_xpol EASEGridCell_Array bit flag 4 N/A N/A N/A N/A 4294967294
soil_moisture EASEGridCell_Array real 4 N/A cm3/cm3 0.02 0.5 -9999.0
soil_moisture_change_index EASEGridCell_Array real 4 N/A cm3/cm3 0.0 0.2 -9999.0
soil_moisture_error EASEGridCell_Array real 4 N/A cm3/cm3 0.0 0.2 -9999.0
soil_moisture_kvz EASEGridCell_Array real 4 N/A cm3/cm3 0.02 0.5 -9999.0
soil_moisture_snapshot 1 EASEGridCell_Array real 4 N/A cm3/cm3 0.02 0.5 -9999.0
soil_moisture_snapshot_DVZ 1 EASEGridCell_Array real 4 N/A cm3/cm3 0.02 0.5 -9999.0
soil_moisture_snapshot_shi 1 EASEGridCell_Array real 4 N/A cm3/cm3 0.02 0.5 -9999.0
soil_moisture_time_series EASEGridCell_Array real 4 N/A cm3/cm3 0.02 0.5 -9999.0
spacecraft_overpass_time_seconds EASEGridCell_Array real 8 N/A seconds 0.00000 999999.9 -9999.0
spacecraft_overpass_time_utc EASEGridCell_Array string 24 N/A N/A N/A N/A N/A
surface_flag EASEGridCell_Array bit flag 2 N/A N/A N/A N/A 65534
1 Algorithms that are not currently being used for these data include Snapshot, Dubois/van Zyl (DVZ), and Shi. Thus, the data fields corresponding to these algorithms contain a fill value of -9999.0. 
 


Data Field Definitions [top]

bare_soil_roughness_tabular

Measure of soil roughness from tabular source compiled from published literature.

faraday_rotation_angle

Faraday rotation angle. The Faraday rotation effect is the effect of a magnetic field on the transmission of linearly polarized light through a dispersive medium.

landcover_class

An enumerated type that specifies the predominant surface vegetation found in the grid cell. See Table 4 for landcover classification values.

Table 4. Landcover Classification Values
Value Description
0 Water
1 Evergreen needleleaf forest
2 Evergreen broadleaf forest
3 Deciduous needleleaf forest
4 Deciduous broadleaf forest
5 Mixed forest
6 Closed shrubland
7 Open shrubland
8 Woody savanna
9 Savanna
10 Grassland
11 Mixed forest
12 Closed shrubland
13 Open shrubland
14 Woody savanna
15 Savanna
16 Grassland
>16 TBD

normalized_difference_vegetation_index

A measure of the green character of vegetation. (IR-Red)/(IR+Red)

static_water_body_fraction

The fraction of the area of the 3 km grid cell that is covered by static water based on a Digital Elevation Map.

surface_temperature

Temperature at land surface based on ancillary data.

vegetation_water_content_NDVI

Representative measure of water in the vegetation within the 3 km grid cell based on the Normalized Difference Vegetation Index (NDVI).

vegetation_water_content_RVI

Representative measure of water in the vegetation within the 3 km grid cell based on the radar vegetation index.

altitude_std_dev

The standard deviation of the Earth surface elevation within the 3 km cell.

cell_radar_mode_flag

Bit flags that specify modes or conditions of radar instrument operation that impact the data represented in the SPL2SMA product.

Table 5. Bit Values and Interpretation
Bit Position Bit Value and Interpretation
0 0 = Radar is operating in transmit-receive mode
1 = Radar is operating in receive only mode
1 Always clear (This bit is used to designate the nadir region in Level 1. It is redundant in Level 2.)
2 0 = Cross polarized data are v-pol transmitted, h-pol received.
1 = Cross polarized data are h-pol transmitted, v-pol received.
3 0 = Cross polarized data are consistent within this EASE grid cell.
1 = Cross polarized data are in transition, some are v-pol transmitted, h-pol received, others are h-pol transmitted, v-pol received.
4-15 Always clear (Bits 5 through 7 are reserved for Radar Level 1C use. Bits 8 through 15 are reserved for Level 2 use.)

earth_boresight_azimuth_aft

Mean direction of the projection of the antenna boresight vector on the Earth's surface relative to North for aft looking sigma0s within 3 km cell. Level 1C azimuth is based on instrument coordinate system, not geographical North.

earth_boresight_azimuth_fore

Mean direction of the projection of the antenna boresight vector on the Earth's surface relative to North for forward looking sigma0s within 3 km cell. Level 1C azimuth is based on instrument coordinate system, not geographical North.

kp_hh

Overall error measure for HH-pol σ0 within the 3 km cell based on Level 1C kp values, includes calibration, RFI and contamination effects.

kp_hh_aft

Overall error measure for aft-looking HH-pol σ0 within the 3 km cell based on Level 1C kp values, includes calibration, RFI and contamination effects.

kp_hh_fore

Overall error measure for fore-looking HH-pol σ0 within the 3 km cell based on Level 1C kp values, includes calibration, RFI and contamination effects.

kp_vv

Overall error measure for VV-pol σ0 within the 3 km cell based on Level 1C kp values, includes calibration, RFI and contamination effects.

kp_vv_aft

Overall error measure for aft-looking VV-pol σ0 within the 3 km cell based on Level 1C kp values, includes calibration, RFI and contamination effects.

kp_vv_fore

Overall error measure for fore-looking VV-pol σ0 within the 3 km cell based on Level 1C kp values, includes calibration, RFI and contamination effects.

kp_xpol

Overall error measure for cross-pol σ0 within the 3 km cell based on Level 1C kp values, includes calibration, RFI and contamination effects.

kp_xpol_aft

Overall error measure for aft-looking cross-pol σ0 within the 3 km cell based on Level 1C kp values, includes calibration, RFI and contamination effects.

kp_xpol_fore

Overall error measure for fore-looking cross-pol σ0 within the 3 km cell based on Level 1C kp values, includes calibration, RFI and contamination effects.

sigma0_hh_mean

Mean of 1 km instrument resolution HH-pol σ0 in the 3 km Earth grid cell.

sigma0_hh_mean_aft

Mean of 1 km instrument resolution aft-looking HH-pol σ0 in the 3 km Earth grid cell.

sigma0_hh_mean_fore

Mean of 1 km instrument resolution fore-looking HH-pol σ0 in the 3 km Earth grid cell.

sigma0_hh_std_dev

Standard deviation of 1 km instrument resolution HH-pol σ0 in the 3 km Earth grid cell.

sigma0_hh_std_dev_aft

Standard deviation of 1 km instrument resolution aft-looking HH-pol σ0 in the 3 km Earth grid cell.

sigma0_hh_std_dev_fore

Standard deviation of 1 km instrument resolution fore-looking HH-pol σ0 in the 3 km Earth grid cell.

sigma0_vv_mean

Mean of 1 km instrument resolution VV-pol σ0 in the 3 km Earth grid cell.

sigma0_vv_mean_aft

Mean of 1 km instrument resolution aft-looking VV-pol σ0 in the 3 km Earth grid cell.

sigma0_vv_mean_fore

Mean of 1 km instrument resolution fore-looking VV-pol σ0 in the 3 km Earth grid cell.

sigma0_vv_std_dev

Standard deviation of 1 km instrument resolution VV-pol σ0 in the 3 km Earth grid cell.

sigma0_vv_std_dev_aft

Standard deviation of 1 km instrument resolution aft-looking VV-pol σ0 in the 3 km Earth grid cell.

sigma0_vv_std_dev_fore

Standard deviation of 1 km instrument resolution fore-looking VV-pol σ0 in the 3 km Earth grid cell.

sigma0_xpol_mean

Mean of 1 km instrument resolution cross-pol σ0 in the 3 km Earth grid cell.

sigma0_xpol_mean_aft

Mean of 1 km instrument resolution aft-looking cross-pol σ0 in the 3 km Earth grid cell.

sigma0_xpol_mean_fore

Mean of 1 km instrument resolution fore-looking cross-pol σ0 in the 3 km Earth grid cell.

sigma0_xpol_std_dev

Standard deviation of 1 km instrument resolution cross-pol σ0 in the 3 km Earth grid cell.

sigma0_xpol_std_dev_aft

Standard deviation of 1 km instrument resolution aft-looking cross-pol σ0 in the 3 km Earth grid cell.

sigma0_xpol_std_dev_fore

Standard deviation of 1 km instrument resolution fore-looking cross-pol σ0 in the 3 km Earth grid cell.

EASE_column_index

EASE grid column index of cell on world grid in longitude direction.

EASE_row_index

EASE grid row index of cell on world grid in latitude direction.

bare_soil_roughness_retrieved

Bare soil roughness measure retrieved using the active soil moisture algorithm.

distance_from_nadir

The distance from the center of the 3 km EASE grid cell to the spacecraft's sub-nadir track on the Earth's surface.

latitude

Latitude of the center of the Earth-based grid cell.

longitude

Longitude of the center of the Earth-based grid cell.

num_input_sigma0s_hh

Total number of horizontal polarization sigma0s from the Level 1C product that were used for retrievals in an EASE grid cell.

num_input_sigma0s_vv

Total number of vertical polarization sigma0s from the Level 1C product that were used for retrievals in an EASE grid cell.

num_input_sigma0s_xpol

Total number of cross-polarization sigma0s from the Level 1C product that were used for retrievals in an EASE grid cell.

num_time_series

The number of time-series data used to retrieve soil moisture in the corresponding grid cell.

radar_vegetation_index

Vegetation index derived from radar backscatter.

radar_water_flag3

Radar waterbody flag at 3km.

retrieval_qual_flag

Bit flags that record the conditions and the quality of the soil moisture and freeze/thaw retrieval for the grid cell. See Table 6 for bit flag definitions.

For a listing of retrieval quality flag data fields and their corresponding soil moisture fields, see Table 8.

Table 6. Quality Bit Flag Definitions
Name Bit Position Interpretation of Values (0:off, 1:on)
Retrieval recommended flag 0 0: Use of the soil moisture value retrieved for this pixel is recommended.
1: Use of soil moisture value retrieved for this pixel is not recommended.
Retrieval attempted flag 1 0: The algorithm attempted to retrieve soil moisture for this grid cell.
1: The algorithm did not attempt to retrieve soil moisture for this grid cell.
Retrieval success flag 2 0: Retrieval for this algorithm was successfully executed or the algorithm was not attempted.
1: The retrieval for this algorithm was attempted but failed.
Radar water body detection success flag 3 0: Radar water body detection ran successfully.
1: Unable to detect water bodies using retrieval techniques based on radar.
freeze/thaw retrieval success flag 4 0: freeze/thaw retrieval ran succesfully.
1: Unable to ascertain freeze/thaw conditons.
Radar vegetation index retrieval success flag 5 0: Radar vegetation index retrieval ran successfully.
1: Radar vegetation index retrieval unsuccessful.

retrieval_qual_flag_change_index

Bit flags that record the conditions and the quality of the soil moisture and freeze/thaw retrieval for the grid cell. See Table 6.

For a listing of retrieval quality flag data fields and their corresponding soil moisture fields, see Table 8.

retrieval_qual_flag_cube

Bit flags that record the conditions and the quality of the soil moisture and freeze/thaw retrieval for the grid cell. See Table 6.

retrieval_qual_flag_kvz

Bit flags that record the conditions and the quality of the soil moisture and freeze/thaw retrieval for the grid cell. See Table 6.

For a listing of retrieval quality flag data fields and their corresponding soil moisture fields, see Table 8.

sigma0_qual_flag_hh

Representative quality flags of horizontal polarization sigma0 measures in the grid cell. See Table 7.

Table 7. Sigma Quality Bit Flag Definitions
Name Bit Position Description of Values (0: off, 1: on)
Mean horizontal polarization quality flag 0 0: The mean of the forward looking and aft looking horizontal polarization sigma0s has acceptable quality.
1: The mean of the forward looking and aft looking horizontal polarization sigma0s does not have acceptable quality.
Forward looking horizontal polarization quality flag 1 0: The forward looking horizontal polarization sigma0 has acceptable quality.
1: The forward looking horizontal polarization sigma0 has questionable or poor quality.
Aft looking horizontal polarization quality flag 2 0: The aft looking horizontal polarization sigma0 has acceptable quality.
1: The aft looking horizontal polarization sigma0 has questionable or poor quality.
Mean horizontal polarization range flag 3 0: The mean of the forward looking and aft looking horizontal polarization sigma0s falls within the expected range.
1: The mean of the forward looking and aft looking horizontal polarization sigma0s is out of range.
Forward looking horizontal polarization range flag 4 0: The forward looking horizontal polarization sigma0 falls within the expected range.
1: The forward looking horizontal polarization sigma0 is out of range.
Aft looking horizontal polarization range flag 5 0: The aft looking horizontal polarization sigma0 falls within the expected range.
1: The aft looking horizontal polarization sigma0 is out of range.
Mean horizontal polarization RFI clean flag 6 0: Insignificant RFI detected in the mean of the forward looking and aft looking horizontal polarization sigma0s.
1: RFI level is unsuitably high for the mean of the forward looking and aft looking horizontal polarization sigma0s.
Mean horizontal polarization RFI repair flag 7 0: Some components of the mean of the forward looking and aft looking horizontal polarization sigma0s are based on repairs for RFI contamination.
1: Unable to repair the mean of the forward looking and aft looking horizontal polarization sigma0s for RFI contamination.
Forward looking horizontal polarization RFI clean flag 8 0: Insignificant RFI detected in the forward looking horizontal polarization sigma0s.
1: RFI level is unsuitably high for the forward looking horizontal polarization sigma0s.
Forward looking horizontal polarization RFI repair flag 9 0: At least one of the input forward looking horizontal polarization sigma0s is based on repairs for RFI contamination.
1: Unable to repair the forward looking horizontal polarization sigma0s for RFI contamination.
Aft looking horizontal polarization RFI clean flag 10 0: Insignificant RFI detected in the aft looking horizontal polarization sigma0s.
1: RFI level is unsuitably high for the aft looking horizontal polarization sigma0s.
Aft looking horizontal polarization RFI repair flag 11 0: At least one of the input aft looking horizontal polarization sigma0s is based on repairs for RFI contamination.
1: Unable to repair the aft looking horizontal polarization sigma0s for RFI contamination.
Mean horizontal polarization Faraday Rotation Flag 12 0: Faraday Rotation has little or no impact on the mean of the forward looking and aft looking horizontal polarization sigma0s.
1: Faraday Rotation has significant impact on the mean of the forward looking and aft looking horizontal polarization sigma0s.
Forward looking horizontal polarization Faraday Rotation Flag 13 0: Faraday Rotation has little or no impact on the forward looking horizontal polarization sigma0.
1: Faraday Rotation has significant impact on the forward looking horizontal polarization sigma0.
Aft looking horizontal polarization Faraday Rotation Flag 14 0: Faraday Rotation has little or no impact on the aft looking horizontal polarization sigma0.
1: Faraday Rotation has significant impact on the aft looking horizontal polarization sigma0.
Mean horizontal polarization Kp flag 15 0: Kp for the mean of the forward and aft looking horizontal polarization sigma0s is acceptably low.
1: Kp for the mean of forward and aft looking horizontal polarization sigma0s is unacceptably high.
Forward looking horizontal polarization Kp flag 16 0: Kp for the forward looking horizontal polarization sigma0 is acceptably low.
1: Kp for the forward looking horizontal polarization sigma0 is unacceptably high.
Aft looking horizontal polarization Kp flag 17 0: Kp for the aft looking horizontal polarization sigma0 is acceptably low.
1: Kp for the aft looking horizontal polarization sigma0 is unacceptably high.

sigma0_qual_flag_vv

Representative quality flags of vertical polarization sigma0 measures in the grid cell. See Table 7.

sigma0_qual_flag_xpol

Representative quality flags of cross polarization sigma0 measures in the grid cell. See Table 7.

soil_moisture

Retrieved soil moisture for the Earth-based grid cell retrieved using the time series algorithm. The soil_moisture field is internally linked to the soil_moisture_time_series field produced by the baseline algorithm. At present, the operational SPL2SMA Science Production Software (SPS) produces and stores soil moisture retrieval results from two of the five soil moisture algorithms listed in Table 3: soil_moisture_time_series and soil_moisture_kvz. For a listing of the soil moisture data fields and the corresponding retrieval quality flag data fields, see Table 8.

Table 8. Soil Moisture Data Fields and Corresponding Retrieval Quality Flags
Soil Moisture Data Field Internal Link Corresponding Retrieval Quality Flag Data Field
soil_moisture soil_moisture_time_series retrieval_qual_flag
soil_moisture_change_index retrieval_qual_flag_change_index
soil_moisture_kvz retrieval_qual_flag_kvz
soil_moisture_snapshot1 N/A N/A
soil_moisture_snapshot_DVZ1 N/A N/A
soil_moisture_snapshot_shi1 N/A N/A
soil_moisture_time_series retrieval_qual_flag

1 Algorithms that are not currently being used for SPL2SMA data include Snapshot, Dubois/van Zyl (DVZ), and Shi. Thus, the data fields corresponding to these algorithms contain a fill value of -9999.0.

soil_moisture_change_index

Retrieved normalized change in soil moisture. For a listing of the soil moisture data fields and the corresponding retrieval quality flag data fields, see Table 8.

soil_moisture_error

Net uncertainty measure of soil moisture measure for the Earth-based grid cell. Calculation method is TBD. May be replaced by other quality indicators.

soil_moisture_kvz

Retrieved soil moisture for the Earth-based grid cell retrieved using the Kim/van Zyl time series algorithm. At present, the operational SPL2SMA Science Production Software (SPS) produces and stores soil moisture retrieval results from two of the five soil moisture algorithms listed in Table 3: soil_moisture_time_series and soil_moisture_kvz. For a listing of the soil moisture data fields and the corresponding retrieval quality flag data fields, see Table 8.

soil_moisture_snapshot

Representative soil moisture measurement for the Earth-based grid cell, retrieved using the snapshot algiorithm. For a listing of the soil moisture data fields and the corresponding retrieval quality flag data fields, see Table 8.

soil_moisture_snapshot_DVZ

Retrieved soil moisture for the Earth-based grid cell, retrieved using the Dubois/van Zyl snapshot algorithm. For a listing of the soil moisture data fields and the corresponding retrieval quality flag data fields, see Table 8.

soil_moisture_snapshot_shi

Retrieved soil moisture for the Earth-based grid cell, retrieved using the Shi snapshot algorithm. For a listing of the soil moisture data fields and the corresponding retrieval quality flag data fields, see Table 8.

soil_moisture_time_series

Retrieved soil moisture for the Earth-based grid cell retrieved using the time series algorithm. The soil_moisture field is internally linked to the soil_moisture_time_series field produced by the baseline algorithm. At present, the operational SPL2SMA Science Production Software (SPS) produces and stores soil moisture retrieval results from two of the five soil moisture algorithms listed in Table 3: soil_moisture_time_series and soil_moisture_kvz. For a listing of the soil moisture data fields and the corresponding retrieval quality flag data fields, see Table 8.

spacecraft_overpass_time_seconds

Number of seconds since a specified epoch (J2000) that represents the spacecraft overpass relative to ground swath.

spacecraft_overpass_time_utc

Time of spacecraft overpass relative to ground swath in UTC.

surface_flag

Bit flags that record ambient surface conditions for the grid cell. See Table 9.

Table 9. Surface Quality Bit Flag Definitions
Name Bit Position Description of Values (0: off, 1: on)
3 km static water body flag 0 0: The fraction of the 3 km grid cell area that is over a permanent water body is less than metadata element PermanentWaterBodyThreshold. Determined by DEM.
1: The fraction of the 3 km grid cell area that is over a permanent water body is greater than or equal to metadata element PermanentWaterBodyThreshold. Determined by DEM.
3 km radar water body detection flag 1 0: Radar retrieval algorithm did not detect significant surface water within the 3 km grid cell.
1: Radar retrieval algorithm detected significant surface water withing the 3 km grid cell.
3 km urban area flag 2 0: The fraction of the 3 km grid cell area that is over urban development is less than metadata element UrbanAreaThreshold.
1: The fraction of the 3 km grid cell area that is over urban development is greater than or equal to metadata element UrbanAreaThreshold.
3 km precipitation flag 3 0: No precipitation detected within the 3 km grid cell when data were being acquired.
1: Precipitation detected within the 3 km grid cell when data were being acquired
3 km snow or ice flag 4 0: No snow or ice detected within the 3 km grid cell.
1: Snow and/or ice were detected within the 3 km grid cell.
3 km permanent snow or ice flag 5 0: The fraction of the 3 km grid cell area that is over permanent snow or ice is less than a specified algorithmic threshold.
1: The fraction of the 3 km grid cell area that is over permanent snow or ice is greater than or equal to a specified algorithmic threshold.
3 km frozen ground flag 6 0: No frozen ground detected within the 3 km grid cell.
1: Frozen ground detected within the 3 km grid cell.
3 km mountainous terrain flag 7 0: The variability of land elevation in the 3 km grid cell is less than metadata element MountainousTerrainThreshold.
1: The variability of land elevation in the 3 km grid cell is greater than or equal to metadata element MountainousTerrainThreshold.
3 km dense vegetation flag 8 0: The vegetation density within the 3 km grid cell is less than metadata element DenseVegetationThreshold.
1: The vegetation density within the 3 km grid cell area is greater than or equal to metadata element DenseVegetationThreshold.
3 km nadir region flag 9 0: Data within the the grid cell were not acquired in the nadir region of the swath where sigma0s may not meet the 3 km resolution requirement.
1: A significant fraction (TBD) of the 3 km grid cell data were acquired within the nadir region of the swath where sigma0s may not meet the 3 km resolution requirement.
3 km coastal mask flag 10 0: Data within the the grid cell were not acquired in the coastal region of the large water bodies where especially brightness temperature on land may get severly contaminated due to presense of water.
1: Data within the the grid cell were acquired in the coastal region of the large water bodies where especially brightness temperature on land may get severly contaminated due to presense of water.

Fill/Gap Values [top]

SMAP data products employ fill and gap values to indicate when no valid data appear in a particular data element. Fill values ensure that data elements retain the correct shape. Gap values locate portions of a data stream that do not appear in the output data file.

Fill values appear in the SMAP SPL2SMA Product when the SPL2SMA SPS can process some, but not all, of the input data for a particular swath grid cell. Fill data may appear in the product in any of the following circumstances:

  • One of Science Production Software (SPS) executables that generate the SMAP SPL2SMA Product is unable to calculate a particular science or engineering data value. The algorithm encounters an error. The error disables generation of valid output. The SPS reports a fill value instead.
  • Some of the required science or engineering algorithmic input are missing. Data over the region that contributes to particular grid cell may appear in only some of the input data streams. Since data are valuable, the SPL2SMA Product records any outcome that can be calculated with the available input. Missing data appear as fill values.
  • Non-essential information is missing from the input data stream. The lack of non-essential information does not impair the algorithm from generating needed output. The missing data appear as fill values.
  • Fill values appear in the input radar L1C_S0_Hires product. If only some of the input that contributes to a particular grid cell is fill data, the SPL2SMA SPS will most likely be able to generate some output. However, some portion of the SPL2SMA output for that grid cell may appear as fill values.

SMAP data products employ a specific set of data values to connote that an element is fill. The selected values that represent fill are dependent on the data type.

No valid value in the SPL2SMA product is equal to the values that represent fill. If any exceptions should exist in the future, the SPL2SMA content will provide a means for users to discern between elements that contain fill and elements that contain genuine data values. This document will also contain a description of the method used to ascertain which elements are fill and which elements are genuine.

The SPL2SMA product records gaps when entire frames within the time span of a particular data granule do not appear. Gaps can occur under one of two conditions:

  • One or more complete frames of data are missing from all data streams.
  • The subset of input data that is available for a particular frame is not sufficient to process any frame output.

The Level SPL2SMA Product records gaps in the product level metadata. The following conditions will indicate that no gaps appear in the data product:

  • Only one instance of the attributes Extent/rangeBeginningDateTime and Extent/rangeEndingDateTime will appear in the product metadata.
  • The character string stored in metadata element Extent/rangeBeginningDateTime will match the character string stored in metadata element OrbitMeasuredLocation/halfOrbitStartDateTime.
  • The character string stored in metadata element Extent/rangeEndingDateTime will match the character string stored in metadata element OrbitMeasuredLocation/halfOrbitStopDateTime.

One of two conditions will indicate that gaps appear in the data product:

  • The time period covered between Extent/rangeBeginningDateTime and Extent/RangeEndingDateTime does not cover the entire half orbit as specified in OrbitMeasuredLocation/halfOrbitStartDateTime and OrbitMeasuredLocation/halfOrbitStartDateTime.
  • More than one pair of Extent/rangeBeginningDateTime and Extent/rangeEndingDateTime appears in the data product. Time periods within the time span of the half orbit that do not fall within the sets of Extent/rangeBeginningDateTime and Extent/rangeEndingDateTime constitute data gaps.

Notations [top]

Table 10 lists the notations used in this document.

Table 10. Notation Definitions
Notation Definition
Int8 8-bit (1-byte) signed integer
Int16 16-bit (2-byte) signed integer
Int32 32-bit (4-byte) signed integer
Uint8 8-bit (1-byte) unsigned integer
Uint16 16-bit (2-byte) unsigned integer
Float32 32-bit (4-byte) floating-point integer
Float64 64-bit (8-byte) floating-point integer
Char 8-bit character
H-pol Horizontally polarized
V-pol Vertically polarized