Data Fields - SMAP L4 Global Daily 9 km Carbon Net Ecosystem Exchange, Version 4

This page provides a description of all data fields within the SMAP L4 Global Daily 9 km Carbon Net Ecosystem Exchange (SPL4CMDL) product. The data are provided in the following main HDF5 groups:

  • Root Data - time and space coordinate data sets are not stored in a particular group
  • EC — Environmental Constraints
  • GEO — Geolocation Information
  • GPP — Gross Primary Production
  • NEE — Net Ecosystem Exchange
  • QA — Quality Assurance
  • RH — Heterotrophic Respiration
  • SOC — Soil Organic Carbon
  • Metadata

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

SMAP Level-4 carbon files include HDF5 groups that contain six primary variables: EC, GEO, GPP, NEE, RH, and SOC. With the exception of EC and GEO, each group includes data fields for eight Plant Function Type (PFT) classes (refer to Table 9). Note that the QA variables also includes PFT classes. All output variables are summarized in the following tables.

Root Data [top]

Table 1. Data Fields for Root Data
Data Field Name Type Unit Valid Min Valid Max Fill/Gap Value
EASE2_global_projection string N/A N/A N/A N/A
x Float64 m -17367531 17367531 0.0
y Float64 m -7342231 7342231 0.0

Environmental Constraints (EC) [top]

Table 2. Data Fields for EC Group
Data Field Name Type Bit Unit Valid Min Valid Max Fill/Gap Value Dimensions
emult_mean Float32 2 percent 0.0 100.0 -9999.0 1624 x 3856
frozen_area Float32 2 percent 0.0 100.0 -9999.0 1624 x 3856
tmult_mean Float32 2 percent 0.0 100.0 -9999.0 1624 x 3856
wmult_mean Float32 2 percent 0.0 100.0 -9999.0 1624 x 3856


Geolocation Information (GEO) [top]

Table 3. Data Fields for GEO Group
Data Field Name Type Bit Unit Valid Min Valid Max Fill/Gap Value Dimensions
latitude Float32 2 decimal degree -89.999 89.999 -9999.0 1624 x 3856
longitude Float32 2 decimal degree -179.999 179.999 -9999.0 1624 x 3856


Gross Primary Production (GPP) [top]

Table 4. Data Fields for GPP Group
Data Field Name Type Bit Unit Valid Min Valid Max Fill/Gap Value Dimensions
gpp_mean Float32 2 gCm-2day-1 0.0 30.0 -9999.0 1624 x 3856
gpp_pft[1-8]_mean Float32 2 gCm-2day-1 0.0 30.0 -9999.0 1624 x 3856
gpp_std_dev Float32 2 gCm-2day-1 0.0 30.0 -9999.0 1624 x 3856


Net Ecosystem Exchange (NEE) [top]

Table 5. Data Fields for NEE Group
Data Field Name Type Bit Unit Valid Min Valid Max Fill/Gap Value Dimensions
nee_mean Float32 2 gCm-2day-1 -30.0 20.0 -9999.0 1624 x 3856
nee_pft[1-8]_mean Float32 2 gCm-2day-1 -30.0 20.0 -9999.0 1624 x 3856
nee_std_dev Float32 2 gCm-2day-1 -30.0 20.0 -9999.0 1624 x 3856


Quality Assurance (QA) [top]

Table 6. Data Fields for QA Group
Data Field Name Type Bit Unit Valid Min Valid Max Fill/Gap Value Dimensions
carbon_model_bitflag Uint16 2 dimensionless 0.0 65534 65534 1624 x 3856
nee_rmse_mean Float32 2 gCm-2day-1 0.0 20.0 -9999.0 1624 x 3856
nee_rmse_pft[1-8]_mean Float32 2 gCm-2day-1 0.0 20.0 -9999.0 1624 x 3856
qa_count Uint8 2 dimensionless 0 81.0 254 1624 x 3856
qa_count_pft[1-8] Uint8 2 dimensionless 0 81.0 254 1624 x 3856


Heterotrophic Respiration (RH) [top]

Table 7. Data Fields for RH Group
Data Field Name Type Bit Unit Valid Min Valid Max Fill/Gap Value Dimensions
rh_mean Float32 2 gCm-2day-1 0.0 20.0 -9999.0 1624 x 3856
rh_pft[1-8]_mean Float32 2 gCm-2day-1 0.0 20.0 -9999.0 1624 x 3856
rh_std_dev Float32 2 gCm-2day-1 0.0 20.0 -9999.0 1624 x 3856


Soil Organic Carbon (SOC) [top]

Table 8. Data Fields for SOC Group
Data Field Name Type Bit Unit Valid Min Valid Max Fill/Gap Value Dimensions
soc_mean Float32 2 gCm-2 0.0 25000.0 -9999.0 1624 x 3856
soc_pft[1-8]_mean Float32 2 gCm-2 0.0 25000.0 -9999.0 1624 x 3856
soc_std_dev Float32 2 gCm-2 0.0 25000.0 -9999.0 1624 x 3856


Metadata [top]

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


Data Field Definitions [top]
 

EASE2_global_projection

Defines the parameters of the cylindrical 9 km Earth-fixed EASE-Grid 2.0 projection and the mapping from latitude/longitude to grid-native coordinates

x
The x coordinate values from the cylindrical 9 km Earth-fixed EASE-Grid 2.0 projection

y
The y coordinate values from the cylindrical 9 km Earth-fixed EASE-Grid 2.0 projection

emult_mean

Environmental-constraint multiplier. PFT class designations are listed in Table 8.

frozen_area

Frozen area percentage (environmental-constraint). Mean frozen_area, per 9 x 9 km pixel, not distinguished by PFT (units = percent constraint; min=0 fully constrained; max = 100.0 not constrained).

tmult_mean

Environmental-constraint on temperature.

wmult_mean

Environmental-constraint on moisture.

latitude

Latitude (north..south) coordinates in decimal degrees.

longitude

Longitude (west..east) coordinates in decimal degrees.

gpp_mean

Global daily 9km Gross Primary Productivity (GPP) mean.

gpp_pft_[1-8]_mean

Mean value of GPP for pixels classified as PFT class [1-8]. PFT class designations are listed in Table 9.

Table 9. PFT Classes
Class Designation
1 Evergreen Needleleaf
2 Evergreen Broadleaf
3 Deciduous Needleleaf
4 Deciduous Broadleaf
5 Shrub
6 Grass
7 Cereal Crop
8 Broadleaf Crop

gpp_std_dev

Global daily 9km Gross Primary Productivity (GPP) standard deviation.

nee_mean

Global daily 9km Net Ecosystem Exchange (mean).

nee_pft_[1-8]_mean

Mean value of NEE for pixels classified in PFT classes 1 through 8. The PFT class designations are listed in Table 9.

nee_std_dev

Global daily 9km Net Ecosystem Exchange standard deviation.

carbon_model_bitflag

Carbon model quality bitflags. Refer to Table 7 in the SPL4CMDL user guide for information on bit flags. A copy of Table 7 is also is included as an attribute called legend_carbon_model_bitflag data field for quick reference. 

nee_rmse_mean

NEE unbiased RMSE estimate (units: gCm^-2day^-1).

nee_rmse_pft[1-8]_mean

NEE unbiased RMSE estimate (units: gCm-2day-1) for PFT class [1-8]. PFT class designations are listed in Table 9.

qa_count

Carbon model QA count 0 to 81 (overall).

qa_count_pft[1-8]

QA count for PFT class [1-8]. PFT class designations are listed in Table 8.

rh_mean

Mean heterotrophic respiration (Rh) value, not distinguished by PFT; in gCm-2day-1 units, (valid_min=0.0,valid_max=20.0).

rh_pft_[1-8]_mean

Mean value of Rh for pixels classified as PFT class [1-8]. PFT class designations are listed in Table 9.

rh_std_dev

Global daily 9km heterotrophic respiration standard deviation.

soc_mean

Global daily 9km soil organic carbon mean.

soc_pft[1-8]_mean

Mean value of SOC for pixels classified as PFT class [1-8]. PFT class designations are listed in Table 9.

soc_std_dev

Global daily 9km soil organic carbon standard deviation.

Fill/Gap Values [top]

SMAP data products employ fill and gap values to indicate when no valid data appear in a particular data field. Fill values ensure that data fields retain the correct dimension. Gap values locate portions of a data stream that do not appear in the output data file. Fill values appear in the SPL4CMDL data product over ocean and water surfaces. SMAP data products employ a specific set of data values to connote that a field is fill. The selected values that represent fill are dependent on the data type.

No valid value in the SPL4CMDL data product is equal to the values that represent fill. If any exceptions should exist in the future, the SPL4CMDL content will provide a means for users to discern between fields that contain fill and fields that contain genuine data values. Operationally, software should not attempt to ever test two floating point values for equality, but instead test two given values using a relational inequality operator and a tolerance-based difference in absolute values (e.g. if abs(a-b) <= 1E-14) method.

For discrete categorical variables such as the bit-flags (carbon_bitflag and carbon_qual_flag_pft[1-8]), all values are defined, therefore no missing data values are expected with these variables. For the analytical variables, the fPAR climatology provides a fallback input source to help assure there are no spatio-temporal gaps in the modeled data record. Therefore no gaps are expected to occur in the SPL4CMDL output data stream.

Acronyms and Abbreviations [top]

Table 9 lists the acronyms and abbreviations used in this document.

Table 9. Acronyms and Abbreviations
Abbreviation Definition
Char 8-bit character
Int8 8-bit (1-byte) signed integer
Int16 16-bit (2-byte) signed integer
Int32 32-bit (4-byte) signed integer
EC Environmental Constraints
Float32 32-bit (4-byte) floating-point integer
Float64 64-bit (8-byte) floating-point integer
fPAR Fraction of Photosynthetically Active Radiation
GEO Geolocation Information
GPP Gross Primary Production
N/A Not Applicable
NEE Net Ecosystem Exchange
PFT Plant Function Type
QA Quality Assurance
RH Heterotrophic Respiration
SOC Soil Organic Carbon
Uint8 8-bit (1-byte) unsigned integer
Uint16 16-bit (2-byte) unsigned integer
UTC Universal Coordinated Time