Changes to this version include:

• Transitioned to Validated-Stage 2
• Calibration parameters were adjusted to reduce calibration jumps and drift previously present in the Beta-release; as a result, calibration now meets its less than 0.4 K/month stability back to 31 March 2015
• Additional bit-error checking was performed on Level-0 instrument telemetry

Version 2

2016-12-07 (10:31) to 2017-04-24 (11:00)

Version 2

2017-04-24 (10:56) to 2017-09-06 (16:52)

• Processing capabilities for the upcoming SMAP/Sentinel-1 radiometer/radar soil moisture product
• SPL1BTB processing change to Atmospheric Correction to ensure proper unit conversion
• Changes to resolve bugs that were causing SPL1BTB_E processing to fail
• Note: Temporal coverage for CRID R15060 varies slightly; though the majority of R15060 files begin at 2017-04-24 (11:00), some R15060 files appear earlier in the time series. 

2017-09-03 (21:36) to 2017-11-14 (23:14)

• Updated compiler optimization flag in radiometer processor to reduce run time
• Compiled optimization flags
• Bug fix for initialization error (error surfaced by optimization flags)
• Note that the data content/quality has not changed

Version 2

2017-12-10 (17:54) to 2018-03-14 (19:57)

2018-03-14 (15:51) to 2018-06-03 (23:50)

R15182

Changes to this version include:

• Transitioned to Validated-Stage 1
• Using SPL1BTB V2 data as input, inherited all changes and improvements of the new version

• Updated reflector thermal model
• Reflector emissivity value back to baseline
• All calibration coefficients updated back to 3/31/15
• Direct Galaxy quality flag changed: set when s/c nadir > 5 degrees
• Reflected Sun quality flag changed: set when specular solar theta <15 degrees
• Sea ice fraction computation implemented

2016-12-07 (10:31) to 2017-04-24 (08:32)

2017-04-24 (08:28) to 2017-09-06 (16:52)

• Processing capabilities for the upcoming SMAP/Sentinel-1 radiometer/radar soil moisture product
• SPL1BTB processing change to Atmospheric Correction to ensure proper unit conversion
• Changes to resolve bugs that were causing SPL1BTB_E processing to fail
• Note: Temporal coverage for CRID R15060 varies slightly; though the majority of R15060 files begin at 2017-04-24 (11:00), some R15060 files appear earlier in the time series. 

2017-09-03 (21:36) to 2017-11-14 (23:14)

• Updated compiler optimization flag in radiometer processor to reduce run time
• Compiled optimization flags
• Bug fix for initialization error (error surfaced by optimization flags)
• Note that the data content/quality has not changed

2018-01-09 (21:35)

2017-12-10 (17:54) to 2018-03-14 (19:57)

2018-03-14 (15:51) to 2018-06-04 (17:04)

2018-03-14

2018-06-14 (15:50)

Changes to this version include:

• Added procedure to correct brightness temperatures for water/land contamination near coastlines. New data fields for this correction include: footprint_surface_status, surface_water_fraction_mb_h, surface_water_fraction_mb_v, tb_h_surface_corrected, and tb_v_surface_corrected.
• Improved Level-1 calibration coefficients and reflected galaxy correction. To refine reflected galaxy correction over ocean, NOAA NCEP ocean roughness data have been added (wind_direction_ancillary, wind_speed_ancillary).

Changes to this version include:

• Transitioned to Validated-Stage 2
• Using SPL1BTB V2 Validated data as input, inherited all changes and improvements of the new version

• Uses updated SPL1BTB V3 Validated data as input
• Updated processing to produce SPL1CTB data files when partial half-orbit input files are present

Version 3

2015-03-31 (16:28) to 2017-04-23 (00:32)

Version 3

2017-04-23 (00:28) to 2017-09-06 (16:52)

• Processing capabilities for the upcoming SMAP/Sentinel-1 radiometer/radar soil moisture product
• SPL1BTB processing change to Atmospheric Correction to ensure proper unit conversion
• Changes to resolve bugs that were causing SPL1BTB_E processing to fail
• Note: Temporal coverage for CRID R15060 varies slightly; though the majority of R15060 files begin at 2017-04-24 (11:00), some R15060 files appear earlier in the time series. 

2017-09-03 (21:36) to 2017-11-14 (23:14)

• Updated compiler optimization flag in radiometer processor to reduce run time
• Compiled optimization flags
• Bug fix for initialization error (error surfaced by optimization flags)
• Note that the data content/quality has not changed

2017-09-03

No science change. CRID incremented to coincide with an update to the radiometer reflector ancillary file for January and February 2018.

2018-06-04 (17:04)

2018-06-14 (15:50)

Version 1

2015-03-31 (16:28) to 2017-04-24 (00:20)

2016-12-07

Version 1

2017-04-24 (00:16) to 2017-09-06 (16:52)

• Processing capabilities for the upcoming SMAP/Sentinel-1 radiometer/radar soil moisture product
• SPL1BTB processing change to Atmospheric Correction to ensure proper unit conversion
• Changes to resolve bugs that were causing SPL1BTB_E processing to fail
• Note: Temporal coverage for CRID R15060 varies slightly; though the majority of R15060 files begin at 2017-04-24 (11:00), some R15060 files appear earlier in the time series. 

2017-04-24

2017-09-03 (21:36) to 2017-11-14 (23:14)

• Updated compiler optimization flag in radiometer processor to reduce run time
• Compiled optimization flags
• Bug fix for initialization error (error surfaced by optimization flags)
• Note that the data content/quality has not changed

2018-01-08 (23:26)

2017-10-26

No science change. CRID incremented to coincide with an update to the radiometer reflector ancillary file for January and February 2018.

2018-06-04 (17:04)

2015-03-31 (16:28) to 2018-06-14 (13:22)

Changes to this version include:

• Uses SPL1CTB V2 Validated-Stage 1 data as input
• Corrects the retrieval quality flag error

2015-04-13 (00:41) to 2015-12-31 (23:18)

2015-03-31 (16:28) to 2016-12-07 (05:40)

Changes to this version include:

• Transitioned to Validated-Stage 2
• Uses updated SPL1CTB V3 Validated data as input

2015-03-31 (16:28) to 2017-04-23 (00:32)

Changes to this version include:

• Added 6:00 p.m. ascending half orbits, which provide:
  • More frequent regional/global coverage (critical in flood monitoring)
  • Soil moisture diurnal variability information (useful in data assimilation systems)
  • Consistency with other similar satellite-based soil moisture products
• Contains frozen ground flag (bit 7 of surface_flag) derived using Normalized Polarization Ration (NPR)-based SMAP passive freeze-thaw retrieval; replaces former SMAP radar-based freeze/thaw flag

2017-04-23 (00:28) to 2017-09-01 (23:39)

• Processing capabilities for the upcoming SMAP/Sentinel-1 radiometer/radar soil moisture product
• SPL1BTB processing change to Atmospheric Correction to ensure proper unit conversion
• Changes to resolve bugs that were causing SPL1BTB_E processing to fail
• Note: Temporal coverage for CRID R15060 varies slightly; though the majority of R15060 files begin at 2017-04-24 (11:00), some R15060 files appear earlier in the time series. 

2017-09-02 (00:28) to 2017-10-25 (23:14)

• Updated compiler optimization flag in radiometer processor to reduce run time
• Compiled optimization flags
• Bug fix for initialization error (error surfaced by optimization flags)
• Note that the data content/quality has not changed

2017-09-02

2018-01-08 (23:26)

No science change. CRID incremented to coincide with an update to the radiometer reflector ancillary file for January and February 2018.

2018-06-14 (07:38)

Changes to this version include:

• Level-1B water-corrected brightness temperatures are used in passive soil moisture retrieval. This procedure corrects for anomalous soil moisture values seen near coastlines in the previous version and should result in less rejected data due to waterbody contamination. Five new data fields accommodate this correction: grid_surface_status, surface_water_fraction_mb_h, surface_water_fraction_mb_v, tb_h_uncorrected, and tb_v_uncorrected.
• Improved depth correction for effective soil temperature used in passive soil moisture retrieval; new results are captured in the surface_temperature data field. This correction reduces the dry bias seen when comparing SMAP data to in situ data from the core validation sites.

• Frozen ground flag updated to reflect improved freeze/thaw detection algorithm, providing better accuracy; new results are captured in bit 7 of the surface_flag.

Version 1

2015-03-31 (16:28) to 2017-04-22 (23:43)

Version 1

2017-04-22 (23:39) to 2017-09-05 (23:39)

• Processing capabilities for the upcoming SMAP/Sentinel-1 radiometer/radar soil moisture product
• SPL1BTB processing change to Atmospheric Correction to ensure proper unit conversion
• Changes to resolve bugs that were causing SPL1BTB_E processing to fail
• Note: Temporal coverage for CRID R15060 varies slightly; though the majority of R15060 files begin at 2017-04-24 (11:00), some R15060 files appear earlier in the time series. 

2017-04-24

2017-09-03 (00:16) to 2017-10-25 (23:14)

• Updated compiler optimization flag in radiometer processor to reduce run time
• Compiled optimization flags
• Bug fix for initialization error (error surfaced by optimization flags)
• Note that the data content/quality has not changed

2017-09-03

2018-06-04 (13:47)

2015-03-31 (16:28) to 2018-06-14 (07:38)

Changes to this version include:

• Level-1B water-corrected brightness temperatures are used in passive soil moisture retrieval. This procedure corrects for anomalous soil moisture values seen near coastlines in the previous version and should result in less rejected data due to waterbody contamination. Five new data fields accommodate this correction: grid_surface_status, surface_water_fraction_mb_h, surface_water_fraction_mb_v, tb_h_uncorrected, and tb_v_uncorrected.
• Improved depth correction for effective soil temperature used in passive soil moisture retrieval; new results are captured in the surface_temperature data field. This correction reduces the dry bias seen when comparing SMAP data to in situ data from the core validation sites.

• Frozen ground flag updated to reflect improved freeze/thaw detection algorithm, providing better accuracy; new results are captured in bit 7 of the surface_flag.

This version incorporates a radar calibration update to process data for 13-23 April 2015.

• Transitioned to Validated-Stage 1
• Uses updated SPL1CS0 V3 as input
• Updates to some of the data cubes
• Update of crop database
• Modified iterative bias correction
• Estimation of VWC

2016-04-21

This version incorporates a radar calibration update to process data for 13-23 April 2015

• Transitioned to Validated-Stage 2
• Uses SPL2SMA V3 Validated and SPL2SMP V3 Validated as input
• Snapshot beta parameter estimation
• Updated soil texture files (renormalized cases where sand+clay > 100%)
• Updated default beta parameter

2016-04-21

No science change. CRID incremented to coincide with an update to the radiometer reflector ancillary file for January and February 2018.

2018-06-03 (00:00)

Changes to this version include:

• Implemented a new method of identifying and eliminating spurious sigma0 values in Sentinel-1A/B Level-1 sigma0 data using a hybrid approach that combines a median filter with thresholding. As a result, fewer spurious sigma0 values (mainly due to small man-made structures) bias the aggregated 1 km data.
• Replaced the previous 3 km resolution urban fraction map with a new 1 km map.
• Adjusted the thresholds used with the new 1 km urban fraction map to: 0.25 (no flag), 0.25 – 0.5 (flagged, retrieval performed), and 0.5 (masked, no retrieval). These are provided in bit 3 of the surface_flag data field.
• Adjusted the tau-omega parameters to be consistent with the values used in SPL2SMP/SPL2SMP_E algorithm.
• Implemented minor bug fix to the SMAP and Sentinel-1 overlap computation code.

Changes to this version include:

• Uses updated SPL1CTB SPL2SMP V2 Beta data as input
• Corrects the retrieval quality flag error

• Transitioned to Validated-Stage 2
• Uses updated SPL2SMP V3 Validated data as input version

Changes to this version include:

• Added 6:00 p.m. ascending half orbits, which provide:
  • More frequent regional/global coverage (critical in flood monitoring)
  • Soil moisture diurnal variability information (useful in data assimilation systems)
  • Consistency with other similar satellite-based soil moisture products
• Contains frozen ground flag (bit 7 of surface_flag) derived using Normalized Polarization Ration (NPR)-based SMAP passive freeze-thaw retrieval; replaces former SMAP radar-based freeze/thaw flag

Version 4

2017-04-23 (00:00) to 2017-09-04 (00:00)

• Processing capabilities for the upcoming SMAP/Sentinel-1 radiometer/radar soil moisture product
• SPL1BTB processing change to Atmospheric Correction to ensure proper unit conversion
• Changes to resolve bugs that were causing SPL1BTB_E processing to fail
• Note: Temporal coverage for CRID R15060 varies slightly; though the majority of R15060 files begin at 2017-04-24 (11:00), some R15060 files appear earlier in the time series. 

2017-09-02 (00:00) to 2017-10-25 (00:00)

• Updated compiler optimization flag in radiometer processor to reduce run time
• Compiled optimization flags
• Bug fix for initialization error (error surfaced by optimization flags)
• Note that the data content/quality has not changed

2018-01-08 (00:00)

2018-06-03 (00:00)

2018-06-13 (00:00)

Changes to this version include:

• Level-1B water-corrected brightness temperatures are used in passive soil moisture retrieval. This procedure corrects for anomalous soil moisture values seen near coastlines in the previous version and should result in less rejected data due to waterbody contamination. Five new data fields accommodate this correction: grid_surface_status, surface_water_fraction_mb_h, surface_water_fraction_mb_v, tb_h_uncorrected, and tb_v_uncorrected.
• Improved depth correction for effective soil temperature used in passive soil moisture retrieval; new results are captured in the surface_temperature data field. This correction reduces the dry bias seen when comparing SMAP data to in situ data from the core validation sites.

• Frozen ground flag updated to reflect improved freeze/thaw detection algorithm, providing better accuracy; new results are captured in bit 7 of the surface_flag.

Version 1

2015-03-31 (00:00) to 2017-04-22 (23:59)

Version 1

2017-04-23 (00:00) to 2017-09-05 (00:00)

• Processing capabilities for the upcoming SMAP/Sentinel-1 radiometer/radar soil moisture product
• SPL1BTB processing change to Atmospheric Correction to ensure proper unit conversion
• Changes to resolve bugs that were causing SPL1BTB_E processing to fail
• Note: Temporal coverage for CRID R15060 varies slightly; though the majority of R15060 files begin at 2017-04-24 (11:00), some R15060 files appear earlier in the time series. 

2017-09-03 (00:00) to 2017-10-25 (00:00)

• Updated compiler optimization flag in radiometer processor to reduce run time
• Compiled optimization flags
• Bug fix for initialization error (error surfaced by optimization flags)
• Note that the data content/quality has not changed

2017-09-03

2018-01-09 (00:00) to 2018-03-13 (00:00)

No science change. CRID incremented to coincide with an update to the radiometer reflector ancillary file for January and February 2018.

2018-06-13 (00:00)

Changes to this version include:

• Level-1B water-corrected brightness temperatures are used in passive soil moisture retrieval. This procedure corrects for anomalous soil moisture values seen near coastlines in the previous version and should result in less rejected data due to waterbody contamination. Five new data fields accommodate this correction: grid_surface_status, surface_water_fraction_mb_h, surface_water_fraction_mb_v, tb_h_uncorrected, and tb_v_uncorrected.
• Improved depth correction for effective soil temperature used in passive soil moisture retrieval; new results are captured in the surface_temperature data field. This correction reduces the dry bias seen when comparing SMAP data to in situ data from the core validation sites.

• Frozen ground flag updated to reflect improved freeze/thaw detection algorithm, providing better accuracy; new results are captured in bit 7 of the surface_flag.

This version incorporates a radar calibration update to process data for 13-23 April 2015.

• Transitioned to Validated-Stage 1
• Uses SPL2SMA V3 Validated data as input; inherited all changes and improvements of the new version

This version incorporates a radar calibration update to process data for 13-23 April 2015.

• Transitioned to Validated-Stage 2
• Using SPL2SMAP V3 Validated data as input

2016-04-21

This version incorporates a radar calibration update to process data for 13-23 April 2015.

2015-07-07 (00:00)

• Transitioned to Validated-Stage 2
• Uses SPL1CS0 V3 Validated data as input
• Using full swath except for nadir-anomaly flagged areas to provide better coverage
• Resolved some flag and fillValue errors

2017-04-22 (23:59)

2017-04-23 (00:00) to 2017-09-05 (00:00)

• Processing capabilities for the upcoming SMAP/Sentinel-1 radiometer/radar soil moisture product
• SPL1BTB processing change to Atmospheric Correction to ensure proper unit conversion
• Changes to resolve bugs that were causing SPL1BTB_E processing to fail
• Note: Temporal coverage for CRID R15060 varies slightly; though the majority of R15060 files begin at 2017-04-24 (11:00), some R15060 files appear earlier in the time series. 

2017-09-06 (00:00) to 2017-10-25 (00:00)

• Updated compiler optimization flag in radiometer processor to reduce run time
• Compiled optimization flags
• Bug fix for initialization error (error surfaced by optimization flags)
• Note that the data content/quality has not changed

2018-01-09 (00:00) to 2018-03-13 (00:00)

No science change. CRID incremented to coincide with an update to the radiometer reflector ancillary file for January and February 2018.

2018-06-03 (00:00)

Changes to this version include:

• Implementation of a supplementary single-channel V-pol (SCV) algorithm for areas of lower latitudes where the seasonal difference of the NPR algorithm is too small to be effectively used to discriminate freeze/thaw state; results are captured in the retrieval_quality_flag. This change provides stronger flag agreement between Tair and Tsoil, and for ascending/p.m. versus descending/a.m. overpasses due to physics (e.g. the NPR algorithm response to wet snow over frozen soil in spring). It also addresses an artifact of the validation approach (e.g. soils remain thawed for weeks after freeze onset in fall due to insulation from snow).
• With the addition of the new SCV algorithm to the NPR baseline algorithm, spatial coverage of freeze/thaw data was extended to global. Data are output on a fixed global 36 km EASE-Grid 2.0 and are provided in the Freeze_Thaw_Retrieval_Data_Global group.
• Updated retrieval_quality_flag for water contamination/permanent ice.
• Implementation of false flag mitigation using TB screening and AMSR-E weekly climatology maps, resulting in significantly fewer false flags.

No science change. CRID incremented to coincide with updates to L1-L3 radiometer products. In addition, /Metadata/GridSpatialRepresentation and /Metadata/Extent structures modified to include definitions for both Polar and Global grid metadata parameters.

Validated-Stage 3 (Report)

2017-09-05 (00:00)

• Processing capabilities for the upcoming SMAP/Sentinel-1 radiometer/radar soil moisture product
• SPL1BTB processing change to Atmospheric Correction to ensure proper unit conversion
• Changes to resolve bugs that were causing SPL1BTB_E processing to fail
• Note: Temporal coverage for CRID R15060 varies slightly; though the majority of R15060 files begin at 2017-04-24 (11:00), some R15060 files appear earlier in the time series. 

2017-09-06 (00:00) to 2017-10-25 (00:00)

• Updated compiler optimization flag in radiometer processor to reduce run time
• Compiled optimization flags
• Bug fix for initialization error (error surfaced by optimization flags)
• Note that the data content/quality has not changed

2018-01-09 (00:00) to 2018-03-13 (00:00)

No science change. CRID incremented to coincide with an update to the radiometer reflector ancillary file for January and February 2018.

Changes to this version include:

• Implementation of a supplementary single-channel V-pol (SCV) algorithm for areas of lower latitudes where the seasonal difference of the NPR algorithm is too small to be effectively used to discriminate freeze/thaw state; results are captured in the retrieval_quality_flag. This change provides stronger flag agreement between Tair and Tsoil, and for ascending/p.m. versus descending/a.m. overpasses due to physics (e.g. the NPR algorithm response to wet snow over frozen soil in spring). It also addresses an artifact of the validation approach (e.g. soils remain thawed for weeks after freeze onset in fall due to insulation from snow).
• With the addition of the new SCV algorithm to the NPR baseline algorithm, spatial coverage of freeze/thaw data was extended to global. Data are output on a fixed global 36 km EASE-Grid 2.0 and are provided in the Freeze_Thaw_Retrieval_Data_Global group.
• Updated retrieval_quality_flag for water contamination/permanent ice.
• Implementation of false flag mitigation using TB screening and AMSR-E weekly climatology maps, resulting in significantly fewer false flags.

Input data source changed from SPL1CTB V1 Beta data to SPL1CTB V2 Validated-Stage 1 data.

• Transitioned to Validated-Stage 2
• Using updated SPL1CTB V3 Validated data as input
• Minor bug fixes

Vv2010

2018-06-04 (22:30)

Changes to this version include:

• SMAP observations are now assimilated in Eastern Europe, the Middle East, and East Asia due to expanded coverage of the brightness temperature scaling parameters. The latter are based on two years of SMAP Version 3 brightness temperature observations where the SMOS climatology is unavailable due to RFI.
• An improved version of the model-only Nature Run (NRv4.1) simulation is used to derive the brightness temperature scaling parameters, the model soil moisture initial conditions, and the soil moisture climatology.
• Minor bug fixes.

Changes to this version include:

• The land surface modeling system was revised in the following ways:
  • Improved input parameter data sets for land cover, topography, and vegetation height are based on more recent data sets. Land cover inputs were updated to the GlobCover2009 product, resulting in a slightly different land mask between Version 3 and Version 4. Topographic statistics now rely on observations from the Shuttle Radar Topography Mission. Finally, vegetation height inputs are derived from space-borne lidar measurements.
  • The model background precipitation forcing is rescaled to match the climatology of the Global Precipitation Climatology Project (v2.2), which results in substantial changes in the precipitation and soil moisture climatology in Africa and the high latitudes, where the gauge-based Climate Prediction Center Unified precipitation is not used.
  • SMAP Level-2 soil moisture retrievals and in situ soil moisture measurements from the Soil Climate Analysis Network and U.S. Climate Reference Network were used to calibrate a particular Catchment model parameter that governs the recharge of soil moisture from the model’s root-zone excess reservoir into the surface excess reservoir. Specifically, the replenishment of soil moisture near the surface from below under non-equilibrium conditions was substantially reduced, which brings the model’s surface soil moisture more in line with the SMAP Level-2 and in situ soil moisture.
  • Additional model changes include revisions to the parameters and parameterizations of the surface energy balance and the snow depletion curve.
• The Version 4 brightness temperature scaling parameters are based on eight years of SMOS observations and three years of SMAP observations where the SMOS climatology is unavailable due to radio frequency interference. Note that the calibration of the assimilated SMAP brightness temperatures changed substantially from Version 3 to Version 4.
• Analysis increments are no longer computed for the “catchment deficit” model prognostic variable in the Ensemble Kalman filter update step.
• Minor bug fixes.
• Added x and y coordinate variables [including arrays of EASE-Grid 2.0 coordinate values, Climate and Forecast (CF)-compliant metadata, and HDF-5 dimension scales] as well as an EASE-Grid 2.0 projection grid mapping variable. This augmentation of L4 soil moisture data files improves interoperability and user workflow via ArcGIS/QGIS, OPeNDAP, and programmatic access. Three new data fields accommodate this change: EASE2_global_projection, x, and y. 

Input data source changed from SPL1CTB V1 Beta data to SPL1CTB V2 Validated-Stage 1 data.

• Transitioned to Validated-Stage 2
• Using updated SPL1CTB V3 Validated data as input
• Minor bug fixes

No science change. CRID incremented to coincide with the release of the following: enhanced products, including SPL1CTB_E, SPL2SMP_E, SPL3SMP_E, SPL3FTP_E (Version 1); SPL3FTP (Version 1); and SPL2SMP, SPL3SMP (Version 4).

Validated-Stage 2
(Report)

Vv2030

2016-12-07

Version 3

2015-03-31 (00:00) to 2018-06-04 (21:00)

Changes to this version include:

• SMAP observations are now assimilated in Eastern Europe, the Middle East, and East Asia due to expanded coverage of the brightness temperature scaling parameters. The latter are based on two years of SMAP Version 3 brightness temperature observations where the SMOS climatology is unavailable due to RFI.
• An improved version of the model-only Nature Run (NRv4.1) simulation is used to derive the brightness temperature scaling parameters, the model soil moisture initial conditions, and the soil moisture climatology.
• Minor bug fixes.

Changes to this version include:

• The land surface modeling system was revised in the following ways:
  • Improved input parameter data sets for land cover, topography, and vegetation height are based on more recent data sets. Land cover inputs were updated to the GlobCover2009 product, resulting in a slightly different land mask between Version 3 and Version 4. Topographic statistics now rely on observations from the Shuttle Radar Topography Mission. Finally, vegetation height inputs are derived from space-borne lidar measurements.
  • The model background precipitation forcing is rescaled to match the climatology of the Global Precipitation Climatology Project (v2.2), which results in substantial changes in the precipitation and soil moisture climatology in Africa and the high latitudes, where the gauge-based Climate Prediction Center Unified precipitation is not used.
  • SMAP Level-2 soil moisture retrievals and in situ soil moisture measurements from the Soil Climate Analysis Network and U.S. Climate Reference Network were used to calibrate a particular Catchment model parameter that governs the recharge of soil moisture from the model’s root-zone excess reservoir into the surface excess reservoir. Specifically, the replenishment of soil moisture near the surface from below under non-equilibrium conditions was substantially reduced, which brings the model’s surface soil moisture more in line with the SMAP Level-2 and in situ soil moisture.
  • Additional model changes include revisions to the parameters and parameterizations of the surface energy balance and the snow depletion curve.
• The Version 4 brightness temperature scaling parameters are based on eight years of SMOS observations and three years of SMAP observations where the SMOS climatology is unavailable due to radio frequency interference. Note that the calibration of the assimilated SMAP brightness temperatures changed substantially from Version 3 to Version 4.
• Analysis increments are no longer computed for the “catchment deficit” model prognostic variable in the Ensemble Kalman filter update step.
• Minor bug fixes.
• Added x and y coordinate variables [including arrays of EASE-Grid 2.0 coordinate values, Climate and Forecast (CF)-compliant metadata, and HDF-5 dimension scales] as well as an EASE-Grid 2.0 projection grid mapping variable. This augmentation of L4 soil moisture data files improves interoperability and user workflow via ArcGIS/QGIS, OPeNDAP, and programmatic access. Three new data fields accommodate this change: EASE2_global_projection, x, and y.

Input data source changed from SPL1CTB V1 Beta data to SPL1CTB V2 Validated-Stage 1 data.

Changes to this version include:

• SMAP observations are now assimilated in Eastern Europe, the Middle East, and East Asia due to expanded coverage of the brightness temperature scaling parameters. The latter are based on two years of SMAP Version 3 brightness temperature observations where the SMOS climatology is unavailable due to RFI.
• An improved version of the model-only Nature Run (NRv4.1) simulation is used to derive the brightness temperature scaling parameters, the model soil moisture initial conditions, and the soil moisture climatology.
• Minor bug fixes.

Changes to this version include:

• The land surface modeling system was revised in the following ways:
  • Improved input parameter data sets for land cover, topography, and vegetation height are based on more recent data sets. Land cover inputs were updated to the GlobCover2009 product, resulting in a slightly different land mask between Version 3 and Version 4. Topographic statistics now rely on observations from the Shuttle Radar Topography Mission. Finally, vegetation height inputs are derived from space-borne lidar measurements.
  • The model background precipitation forcing is rescaled to match the climatology of the Global Precipitation Climatology Project (v2.2), which results in substantial changes in the precipitation and soil moisture climatology in Africa and the high latitudes, where the gauge-based Climate Prediction Center Unified precipitation is not used.
  • SMAP Level-2 soil moisture retrievals and in situ soil moisture measurements from the Soil Climate Analysis Network and U.S. Climate Reference Network were used to calibrate a particular Catchment model parameter that governs the recharge of soil moisture from the model’s root-zone excess reservoir into the surface excess reservoir. Specifically, the replenishment of soil moisture near the surface from below under non-equilibrium conditions was substantially reduced, which brings the model’s surface soil moisture more in line with the SMAP Level-2 and in situ soil moisture.
  • Additional model changes include revisions to the parameters and parameterizations of the surface energy balance and the snow depletion curve.
• The Version 4 brightness temperature scaling parameters are based on eight years of SMOS observations and three years of SMAP observations where the SMOS climatology is unavailable due to radio frequency interference. Note that the calibration of the assimilated SMAP brightness temperatures changed substantially from Version 3 to Version 4.
• Analysis increments are no longer computed for the “catchment deficit” model prognostic variable in the Ensemble Kalman filter update step.
• Minor bug fixes.
• Added x and y coordinate variables [including arrays of EASE-Grid 2.0 coordinate values, Climate and Forecast (CF)-compliant metadata, and HDF-5 dimension scales] as well as an EASE-Grid 2.0 projection grid mapping variable. This augmentation of L4 soil moisture data files improves interoperability and user workflow via ArcGIS/QGIS, OPeNDAP, and programmatic access. Three new data fields accommodate this change: EASE2_global_projection, x, and y.

Changes to this version include:

• Transitioned to Validated-Stage 2
• Using SPL4SMAU V2 Validated and SPL4SMGP V2 Validated data as input
• Update to process radiometer data from 2015-03-31 to 2015-04-12
• Some data fields renamed from *_av to *_mean
• Updated to have have continuous RMSE-based "quality" fields instead of the categorical quality flag in V1

2018-06-04 (00:00)

Changes to this version include:

• Uses dynamic 8-day fPAR inputs obtained from the latest (Collection 6) MODIS fPAR record at 500 m resolution. The preprocessor was updated to handle the finer resolution MODIS Collection 6 inputs, which are interpolated to 1 km resolution prior to model processing. The prior (Version 2) processor used MODIS Collection 5 fPAR inputs, which were derived at 1 km resolution.
• Updated the ancillary MODIS fPAR 8-day climatology used for fPAR gap-filling as an L4C model preprocessing step to reflect new MODIS Collection 6 fPAR inputs. The fPAR climatology is derived from a longer 14-year (2000-2014) MODIS record relative to the original 12-year (2000-2012) Collection 5 fPAR record used in Version 2 processing.
• For each grid cell, a sine-curve-based seasonal fPAR climatology curve is now used to identify and screen anomalous 8-day fPAR variations in the preprocessor. This change reduces impacts of anomalous fPAR temporal variations that may not be captured by the MODIS fPAR product quality control (QC) flags, particularly during seasonal transitions at northern latitudes.
• Updated and recalibrated the ancillary Biome Properties Look-Up Table (BPLUT) and re-initialized the model initial global soil organic carbon (SOC) pools to reflect new MODIS Collection 6 fPAR inputs. The BPLUT calibration was conducted using global historical FLUXNET in situ tower eddy covariance CO2 flux measurement records for representative global land cover types using a similar step-wise calibration procedure employed for the Version 2 product.
• A minor bug fix to the post-processor was made to ensure that all grid cell no-data fill values are identified with a consistent -9999 notation; the prior Version 2 product erroneously assigned some no-data values as -999900.

Changes to this version largely affect model inputs and ancillary files rather than changes to the internal model structure or code. Note that Version 4 is slightly better than Version 3 in RMSE terms, with improvement generally larger for drier sites. Specific changes include:

• The carbon model biome properties lookup table (BPLUT) has been calibrated using an augmented FLUXNET global tower site record which includes more calibration sites (335 sites compared to 228 sites for V3), expanded tower data records extending to at least 2015, and the addition of new tower sites representing more land cover types.
• Revised Level-4 carbon global model calibration and SOC initialization using an extended (2000-2017) MODIS fPAR (V006) record and the latest SMAP Nature Run (NRv7.2) climate data records.
• Implemented minor changes to spatial weighting of calibration tower sites within a model grid cell and reduced the outlier influence on model response curve fitting.