Aquarius L2 Swath Single Orbit Soil Moisture, Version 2

This data set contains Level-2 global soil moisture estimates derived from the NASA Aquarius passive microwave radiometer on the Satélite de Aplicaciones Científicas (SAC-D).

Table of Contents

  1. Contacts and Acknowledgments
  2. Detailed Data Description
  3. Data Access and Tools
  4. Data Acquisition and Processing
  5. References and Related Publications
  6. Document Information

Citing These Data

We kindly request that you cite the use of this data set in a publication using the following citation example. For more information, see our Use and Copyright Web page.

Bindlish, Rajat and Thomas Jackson. 2013. Aquarius L2 Swath Single Orbit Soil Moisture, Version 2, [indicate subset used]. Boulder, Colorado USA: NASA DAAC at the National Snow and Ice Data Center. http://dx.doi.org/10.5067/Aquarius/AQ2_SM.002.

Overview

Platform

SAC-D

Sensor

Aquarius

Spatial Coverage

Global

Spatial Resolution

3 beams of spatial resolution 76 x 94 km (inner), 84 x 120 km (middle) 96 x 156 km (outer)

Temporal Coverage

25 August 2011 to present

Temporal Resolution

7 days global coverage

Parameters

Soil moisture estimate
Brightness temperature at the surface
Backscatter coefficient at the surface

Data Format

HDF5

Metadata Access

View Metadata Record

Version

V2. See the Version History section of this document for previous version information.

Get Data

FTP

1. Contacts and Acknowledgments

Investigator(s) Name and Title

Rajat Bindlish and Thomas Jackson
United States Department of Agriculture
Agricultural Research Service
Hydrology and Remote Sensing Laboratory
Beltsville, MD 20705 USA

Technical Contact

NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449  USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
e-mail: nsidc@nsidc.org

Acknowledgements

This work was funded by NASA under the Interagency agreement NNH10AN10I. Tianjie Zhao helped with development of the soil moisture algorithm. The support provided by Michael Cosh, Peggy O'Neill, Thomas Holmes and Wade Crow is acknowledged. We acknowledge the support provided by Gary Lagerloef, David Le Vine, Gene Feldman and the Aquarius Data Processing System group in the implementation of the Aquarius Soil moisture algorithm.

2. Detailed Data Description

Aquarius LeveL-2 Soil Moisture archive products are produced by the NASA Goddard Space Flight Center's Aquarius Data Processing System (ADPS).

Format

The data files are in Hierarchical Data Format 5 (HDF5).

File and Directory Structure

Data files are organized into directories by date. For example,
/2013.09.28/
/2013.09.29/
/2013.09.30/

File Naming Convention

Soil moisture files are named according to the following conventions and as described in Table 1:

Q2013001004300.L2_SOILM_V2.0

Qyyyydddhhmmss.L2_ppppp_vvvv

Where:

Table 1. File Naming Convention
Variable Description
Q Indicates Aquarius instrument
yyyy UTC four-digit year
ddd UTC day of year
hhmmss UTC hours, minutes, and seconds of the first sample block in the product. "Sample block" is defined as the first set of observations from the three Aquarius beams.
L2 Processing level
ppppp Geophysical parameter: SOILM = soil moisture
vvvv Version, e.g. V2.0

Each data file is paired with an XML file of the same name with .XML extension. The XML file contains metadata associated with the data file.

File Size

Data files are approximately 970 KB each.

Spatial Coverage

Spatial coverage is global.

Spatial Resolution

The Aquarius instrument consists of 3 beams of sizes 76 x 94 km (inner beam), 84 x 120 km (middle beam) and 96 x 156 km (outer beam). The total swath width of the 3 beams is about 390 km. Figure 1 shows the position of the Aquarius beams.

Figure 1. Location and 3 dB size of the Aquarius beams.

Temporal Coverage

25 August 2011 to present.

Aquarius/SAC-D data are acquired daily. Aquarius L2 soil moisture products are delivered monthly, typically within the month following data acquisition.

Temporal Resolution

7 days global coverage.

Parameter or Variable

The Single Channel Algorithm (SCA) is used to estimate soil moisture using Aquarius brightness temperature observations. The SCA is applied to the individual Aquarius footprint brightness temperature observations (L2) to produce a swath-based time-order product. Each swath is stored in a separate file. Files are divided into the groups of attributes shown in Figure 1.

Figure 1. Aquarius soil moisture data file attribute groups.

Parameter Description

Aquarius Data: Attributes contained in the Aquarius Data group are described in Table 2. Each parameter in this group contains 4083 x 3 (Aquarius beams) elements.

Table 2. Aquarius Data Group Description
Name Description Units
anc_sm NCEP GFS GDAS soil moisture. Volumetric Fraction (m3/m3)
anc_subsurf_temp 0-10 cm NCEP GFS sub-surface temperature. The subsurface temperature over the land is the NCEP GFS GDAS product for the layer (0-10 cm) because emission from this layer is most closely correlated with soil moisture. Kelvin
anc_surface_temp NCEP GFS surface temperature. The surface temperature over the ocean is the NOAA OISST (Reynolds) product. Over land, the NCEP GFS GDAS product for the surface layer is used. Kelvin
anc_swe The snow water equivalent from NCEP GFS GDAS. Kg/m2
rad_TbH Aquarius L2 brightness temperature at the Earth surface after atmospheric correction h-pol. Prior to making a correction for roughness. Kelvin
rad_TbV Aquarius L2 brightness temperature at the Earth surface after atmospheric correction v-pol. Prior to making a correction for roughness. Kelvin
rad_ice_frac Fraction of ice contamination. Gain weighted ice fraction integrated over the antenna footprint. The Integration is over the radiometer footprint with 0 = water and 0 = land and 1 = sea ice weighted by the antenna pattern. Computation is made using the NCEP GFS GDAS ice product. Area (m2/m2)
rad_land_frac Fraction of land contamination. The gain weighted land fraction: Integration over the radiometer footprint with 1 = land and 0 = non-land (water and sea ice) weighted by the antenna pattern. Computation is made using the GSFC ODPS (SeaWiFS) 1 km resolution land mask. "Land" includes ice/snow covered land. Area (m2/m2)
rad_sm Aquarius volumetric soil moisture estimates. Volumetric Fraction (m3/m3)
scat_HH_toa Top Of Atmosphere (TOA) scatterometer Normalized Radar Cross Section (NRCS) for HH (transmit horizontal, receive horizontal) polarization. Aquarius L2 normalized radar cross-section at the top of the atmosphere at HH polarization. Decibels
scat_HV_toa TOA Scatterometer NRCS for HV (transmit horizontal, receive vertical) polarization. Aquarius L2 normalized radar cross-section at the top of the atmosphere at HV polarization. Decibels
scat_VH_toa TOA Scatterometer NRCS for VH (transmit vertical, receive horizontal) polarization. Aquarius L2 normalized radar cross-section at the top of the atmosphere at VH polarization. Decibels
scat_VV_toa TOA Scatterometer NRCS for VV (transmit vertical, receive vertical) polarization. Aquarius L2 normalized radar cross-section at the top of the atmosphere at VV polarization. Decibels

Aquarius Flags: The Aquarius Flags group contains one set if attributes for radiometer_flags, described in Table 3.

Table 3. radiometer_flags Attributes
Bit Value Name Value Description
0 No SM Retrieval Mv No Soil Moisture retrieval performed
1 Brightness Temp TB TB < 0 or Tb > 320
2 Orbit Maneuver ORBIT ACS mode = 5
3 RFI RFI Tbh > Tbv; Tb > 320
4 Surface Temp TSURF Tb > Tsurf
5 Frozen Ground FROZ NCEP surface or sub-surface temperature below 273.15
6 Snow SNOW NCEP SWE > 10 kg/m2
7 Ice ICE NCEP ice fraction > 0.1
8 NDVI NDVI MODIS NDVI climatology flag
9 Dense Vegetation VEG Vegetation Water Content > 5 kg/m2
10 Urban URBAN IGBP Land Cover
11 Soil SOIL Invalid Soil Texture data
12 Water WATER Land Fraction < 0.99

Block Attributes: Parameters contained in the Block Attributes group are described in Table 4. Each parameter in this group contains 4083 x 1 elements.

Table 4. Block Attributes Group Description
Name Description Units
sec Mid-block times of Aquarius physical parameter values in seconds of day. Seconds
secGPS GPS time; block times of Aquarius physical parameter values in seconds since the GPS epoch (0 hours UTC on 6 January 1980). Seconds

Navigation: Parameters contained in the Navigation group are described in Table 5.Each parameter in this group contains 4083 x 3 elements, except zang which is 4083 x 1.

Table 5. Navigation Parameter Description
Name Description Units
att_ang Spacecraft roll, pitch, yaw Degrees
beam_clat Beam Center Latitude Degrees
beam_clon Beam Center Longitude Degrees
zang Intra-Orbit Angle Degrees

netCDF metadata are included as global attributes with the Level-2 data files. Table 6 attribute names and values for data file Q2013001004300.L2_SOILM_V2.0. Values that vary from granule to granule are noted.

Table 6. Level-2 Soil Moisture netCDF Metadata General Attributes
Name Value
Product Name Q2013001004300.L2_SOILM_V2.0
Title Aquarius Level-2 Soil Moisture Data
Data Center NASA/GSFC Aquarius Data Processing Center
Mission SAC-D Aquarius
Mission Characteristics Nominal orbit: inclination=98.0 (Sun-synchronous); node=6PM (ascending); eccentricity=<0.002; altitude=657 km; ground speed=6.825 km/sec
Sensor Aquarius
Sensor Characteristics Number of beams=3; channels per receiver=4; frequency 1.413 GHz; bits per sample=16;
instantaneous field of view=6.5 degrees; science data block period=1.44 sec.
Data Type SM
Software ID 1.10
Processing Version
Processing Time 2013123151002000 (varies)
Input Files Q2013001004300_L2_SM.txt (varies)
Processing Control ifile=Q2013001004300_L2_SM.txt ofile=Q2013001004300.L2_SOILM_V2.0 (varies)
_lastModified 2013123151002000 (varies)
Conventions CF-1.6
institution NASA/GSFC OBPG
Start Time 2013001004300 (varies)
Start Year 2013 (varies)
Start Day 1 (varies)
Start Millisec 2580000 (varies)
End Time 2013001022059 (varies)
End Year 2013 (varies)
End Day 1 (varies)
End Millisec 2580000 (varies)
Node Crossing Time 2013001010730000 (varies)
Orbit Node Longitude -105.74653f (varies)
Latitude Units degrees North
Longitude Units degrees East
Orbit Number 8394 (varies)
Cycle Number 71 (varies)
Pass Number 75 (varies)
Nominal Navigation TRUE
Ancillary Files Aquarius_sand_p05d.bin,Aquarius_clay_p05d.bin,Aquarius_bd_p05d.bin,Aquarius_land_cover_5km.dat,
ndvi_max.dat,ndvi_min.dat,ndvi_cmg_12_3.dat,flag_cmg_12_3.dat,ndvi_cmg_01_1.dat

Sample Data Record

Below is a sample of data records from the rad_sm parameter within the Aquarius Data group in the Aquarius soil moisture file: Q2013001004300.L2_SOILM_V2.0.

Figure 2 shows the Aquarius soil moisture estimates using all three beams for July 1, 2012.

Figure 2. Aquarius soil moisture estimates using all three beams July 1, 2012.

3. Data Access and Tools

Get Data

See the NSIDC Aquarius Soil Moisture Order Data page for a list of order options.

Software and Tools

HDF software must be used to read the Aquarius soil moisture files. The following external links provide access to software for reading and viewing HDF5 data files. Please be sure to review instructions on installing and running the programs.

HDFView: Visual tool for browsing and editing HDF4 and HDF5 files.

Panoply netCDF, HDF and GRIB Data Viewer: Cross-platform application. Plots geo-gridded arrays from netCDF, HDF and GRIB datasets.

For additional tools, see the HDF-EOS Tools and Information Center.

4. Data Acquisition and Processing

Aquarius LeveL-2 Soil Moisture archive products are produced by the NASA Goddard Space Flight Center's Aquarius Data Processing System (ADPS).

The soil moisture algorithm runs when the Aquarius data are available. Currently, the Aquarius mission is processing the data monthly.

Theory of Measurements

The Aquarius SCA algorithm uses the L-band horizontally polarized (h-pol) brightness temperature observations due to the higher sensitivity of this channel to soil moisture. H-pol microwave observations are more sensitive to the land surface than the v-pol observations. The Aquarius SCA approach is based on the simplified radiative transfer model developed under the assumption that the canopy and soil temperatures are the same (Jackson 1993). The SCA is applied to the individual Aquarius footprint Level-2 brightness temperature observations to produce a swath-based time-order product (Bindlish and Jackson, 2013). Details on these steps are provided in the Derivation Techniques and Algorithms section.

Data Acquisition Methods

An Aquarius Level-2 Soil Moisture product is generated from one Aquarius Level 2 Science product. The soil moisture product contains physical measurements computed from the Level-2 data at the observed surface locations, along with coordinates of viewed locations and navigation data. This product is stored as one physical HDF file. Each product contains data from one orbit of Aquarius data. An orbit begins as the SAC-D spacecraft crosses the South Pole. The best quality data are selected for each orbit during Level-0 to Level-1A data processing and are then used to create the Level 1A file that is input to the Level-2 science file (Patt 2013).

Derivation Techniques and Algorithms

The derivation techniques and algorithms in this section are from the Aquarius Soil Moisture ATBD Users Guide (Bindlish and Jackson, 2013). The entire ATBD Users Guide may be viewed in PDF format.

Brightness temperatures are converted to emissivity using a surrogate for the effective physical temperature (T) of the emitting layer. The observed emissivity (eobs) is corrected for vegetation and surface roughness to obtain the smooth soil emissivity (esoil). The Fresnel equation is then used to determine the dielectric constant of the soil-water mixture (k). Finally, a dielectric mixing model is used to obtain the soil moisture (SM).

At the L-band frequency used by Aquarius, the brightness temperature of the land surface is proportional to its emissivity (eobs, where eobs = 1 - r) (r = Reflectivity) multiplied by its physical temperature (T). It is assumed that the temperatures of the soil and the vegetation are the same.

Based upon the above, the complete radiative transfer model can be simplified yielding the following expression for the observed TB in Equation 1:

Equation 1 (Equation 1)

Where:

Table 7. Observed Brightness Temperature
Variable Description
TB brightness temperature
eobs observed emissivity

Ancillary surface temperature data from the Numerical Weather Prediction model of the National Centers for Environmental Prediction Global Forecast System (NCEP GFS) is used to correct for the effective physical temperature of the emitting medium.

The emissivity retrieved above is that of the soil as modified by any overlying vegetation and surface roughness. In the presence of vegetation, the observed emissivity is a composite of the soil and vegetation. To retrieve soil water content, it is necessary to isolate the soil surface emissivity (esurf). First, the correction for the presence of vegetation is done based on Jackson and Schmugge (1991), as in Equation 2:

Equation 2 (Equation 2)

Where:

Table 8. Emissivity - Correction For Presence of Vegetation
Variable Description
ω single scattering albedo
γ one-way transmissivity of the canopy
esurf soil surface emissivity

Both the single scattering albedo (ω) and the one-way transmissivity of the canopy (γ) are dependent upon the vegetation structure, polarization and frequency. The transmissivity is a function of the optical depth (τ) of the vegetation canopy:

Equation 3 (Equation 3)

Where:

Table 9. One-way Transmissivity of Canopy
Variable Description
τ optical depth of vegetation canopy
θ system incidence angle

A constant value of the single scattering albedo is used in the Aquarius formulation (ω=0.05). Re-arranging equation 2 yields:

Equation 4 (Equation 4)

The vegetation optical depth is also dependent upon the Vegetation Water Content (VWC). In studies reported in Jackson and Schmugge (1991), it was found that the following functional relationship between the optical depth and vegetation water content could be applied:

Equation 5 (Equation 5)

Where:

Table 10. Relation Between Optical Depth and Vegetation Water Content
Variable Description
b Proportionality value. Depends on vegetation structure and microwave frequency
VWC Vegetation Water Content

The baseline algorithm uses a default global constant value of b = 0.8 for all vegetation classes. The vegetation water content can be estimated using several ancillary data sources. The baseline approach utilizes a set of land cover-based equations to estimate VWC from values of the Moderate Resolution Imaging Spectroradiometer (MODIS) derived Normalized Difference Vegetation Index (NDVI), an index derived from visible-near infrared reflectance data. The baseline approach uses a MODIS NDVI climatology that was derived based on observations from 2001-2010.

The emissivity that results from the vegetation correction is that of the soil surface, including any effects of surface roughness. These effects are removed in order to determine the smooth surface soil emissivity (esoil), which is required for the Fresnel equation inversion. One approach to removing this effect is a model described in Choudhury et al. (1979) that yields the bare smooth soil emissivity:

Equation 6 (Equation 6)

Where:

Table 11. Bare Smooth Soil Emissivity
Variable Description
h h is dependent on the polarization, frequency, and geometric properties of the soil surface. A constant roughness parameter of h = 0.1 is used in the formulation.

The cos2⁡ θ term is often dropped to avoid overcorrecting for roughness.

Emissivity is related to the dielectric properties (ε) of the soil and the viewing or incidence angle. For ease of computational inversion, it is assumed that the real component (εr) of the dielectric constant provides a good approximation of the complex dielectric constant. However, this assumption can be modified if additional evidence is found to support the use of this more complex formulation. The Fresnel equations link the dielectric constant to emissivity. For horizontal polarization:

Equation 7 (Equation 7)

Where:

Table 12. Surface Emissivity - Horizontal Polarization
Variable Description
εr real component of the dielectric constant

The dielectric constant of soil is a composite of the values of its components air, soil, and water, which have greatly different values. A dielectric mixing model is used to relate the estimated dielectric constant to the amount of soil moisture. The Aquarius SCA uses Wang and Schmugge (1980) dielectric mixing model to estimate soil moisture.

Version History

V2.0 is the first version of Aquarius Level-2 Soil Moisture data available from NSIDC. Previous versions were available via the NASA Aquarius Web site (http://aquarius.nasa.gov/).

Error Sources

The current Version 2.0 Aquarius calibration is valid over a narrow range of TB (oceans only) (Piepmeier et al. 2013). The calibration of the Aquarius radiometer over the entire dynamic range is a key element for the successful implementation of the soil moisture algorithm. The Aquarius brightness temperatures are re-calibrated for each beam using co-located and concurrent Soil Moisture Ocean Salinity (SMOS) observations over the entire dynamic range of the satellite. Based upon this analysis, we implemented a correction to the Aquarius brightness temperatures. This involves applying the gain and offsets coefficients computed using the linear fit between the co-located Aquarius and SMOS observations. The Aquarius brightness temperature observations over the oceans were used as a pivot point to compute the slope and the offset. This is an interim fix and will have to be re-evaluated for future versions of the Aquarius TB dataset. Further, details on the warm end bias (Piepmeier et al. 2013) and the re-calibration are available in Bindlish et al, 2013. The re-calibrated brightness temperatures are used in version 2.0 of the soil moisture algorithm. The Aquarius mission is planning to address the full range calibration in the next couple of data releases. These calibration coefficients will be evaluated after each Aquarius data release.

Sensor or Instrument Description

Aquarius/SAC-D is a collaboration between NASA and Argentina's space agency, Comisión Nacional de Actividades Espaciales (CONAE), with participation from Brazil, Canada, France and Italy. The Aquarius instrument was built jointly by NASA's Jet Propulsion Laboratory and NASA's Goddard Space Flight Center.

The Aquarius instrument includes three radiometers and one scatterometer. The radiometers measure brightness temperature at 1.414 GHz in the horizontal and vertical polarizations (TH and TV). The scatterometer is a microwave radar sensor that measure backscatter for surface roughness corrections. Table 13 summarizes instrument characteristics.

Table 13. Aquarius Instrument Characteristics
Instrument Characteristics
3 radiometers in push-broom alignment
  • Frequency: 1.413 GHz
  • Band width: less than or equal to 26 MHz
  • Swath Width: 390 km
  • Science data block period: 1.44 sec
  • Footprints for the beams are: 74 km along track x 94 km cross track, 84 x 120 km, and 96x156 km, yielding a total cross track of 390 km.
  • Beam incidence angles of 29.36, 38.49, and 46.29 degrees incident to the surface. Beams point away from the sun.
Scatterometer
  • Frequency: 1.26 GHz
  • Band Width: 4 MHz
  • Swath Width: 390 km
  • Science data block period: 1.44 sec

SAC-D spacecraft Orbit Parameters:

  • 98 minute sun-synchronous
  • 6 PM ascending orbit, 6 AM descending orbit
  • 657 km equatorial altitude (655 km minimum, 685 km maximum over the orbit)
  • Ground-track repeat interval: 7-day, 103 orbits

5. References and Related Publications

Bindlish, Rajat, and Thomas J. Jackson. 2013. Aquarius Soil Moisture ATBD Users Guide, Version 2.0. Beltsville, Maryland USA: USDA Hydrology and Remote Sensing Lab. (PDF file, 315 KB).

Bindlish, Rajat, Thomas Jackson, Michael Cosh, Tianjie Zhao and Peggy O'Neill. 2013. Global Soil Moisture from the Aquarius Satellite: Description and Initial Assessment. IEEE Geosciences and Remote Sensing Letters (in review).

Bindlish, Rajat, Thomas Jackson, Ruijing Sun, Michael Cosh, Simon Yueh, and Steve Dinardo. 2009. Combined Passive and Active Microwave Observations of Soil Moisture During CLASIC. IEEE Geoscience and Remote Sensing Letters 6(4).

Choudhury, B. J., T. J. Schmugge, A. Chang, and R. W Newton. 1979. Effect of Surface Roughness on the Microwave Emission from Soils, Journal Geophysical Research 84:5699–5706.

Jackson, Thomas J., et al. 2010. Validation of Advanced Microwave Scanning Radiometer Soil Moisture Products. IEEE Transactions on Geoscience and Remote Sensing 48(12).

Jackson, T. J. 1993. Measuring Surface Soil Moisture Using Passive Microwave Remote Sensing. Hydrological Processes 7:139–152.

Jackson, T. J., and T. J Schmugge. 1991. Vegetation Effects on the Microwave Emission of Soils, Remote Sensing of Environment 36(3): 203–212.

Pratt, Frederick S. 2013. Aquarius Level-2 Soil Moisture Data Product. NASA Goddard Space Flight Center Aquarius Project Document AQ-014-PS-0021, Version 2.0.

Piepmeier, Jeffrey, Shannon Brown, Joel Gales, Liang Hong, Gary Lagerloef, David Le Vine, Paolo de Matthaeis, Thomas Meissner, Rajat Bindlish, and Thomas Jackson. 2013. Aquarius Radiometer Post-Launch Calibration for Product Version 2.0, Aquarius Project Document: AQ-014-PS-0015. ftp://podaac-ftp.jpl.nasa.gov/allData/aquarius/docs/v2/AQ-014-PS-0015_AquariusInstrumentCalibratrionDescriptionDocument.pdf.

Wang, J. R., and T. J. Schmugge. 1980. An Empirical Model for the Complex Dielectric Permittivity of Soils as a Function of Water Content, IEEE Transactions on Geoscience and Remote Sensing 18(4): 288–295.

Related Data Collections

Related Web Sites

  • Aquarius Web site at NASA Goddard Space Flight Center (http://aquarius.nasa.gov/)
  • Aquarius Data Web Site at NSIDC (http://nsidc.org//data/aquarius/index.html)
  • Aquarius Web Site at PODAAC (http://podaac.jpl.nasa.gov/aquarius)
  • SMAP Web Site at JPL (http://smap.jpl.nasa.gov)
  • SMOS Website at ESA (http://www.esa.int/Our_Activities/Observing_the_Earth/The_Living_Planet_Programme/Earth_Explorers/SMOS/ESA_s_water_mission_SMOS)

6. Document Information

Acronyms and Abbreviations

The acronyms used in this document are listed in Table 14.

Table 14. Acronyms and Abbreviations
Acronym Description
ACS Attitude Control System
ADPS Aquarius Data Processing System
ATBD Algorithm Theoretical Basis Document
CONAE Comisión Nacional de Actividades Espaciales
GPS Global Positioning System
GSFC Goddard Space Flight Center
HDF5 Hierarchical Data Format 5
HH transmit Horizontal, receive Horizontal
HV transmit Horizontal, receive Vertical
IGBP International Geosphere-Biosphere Programme
L2 Level-2 processing
MODIS Moderate Resolution Imaging Spectroradiometer
NASA National Aeronautics and Space Administration
NCEP GFS National Centers for Environmental Prediction Global Forecast System
NCEP GFS GDAS National Centers for Environmental Prediction Global Forecast System Global Data Assimilation System
NDVI Normalized Difference Vegetation Index
NOAA National Oceanic and Atmospheric Administration
NRCS Normalized Radar Cross Section
ODPS Ocean Data Processing System (ODPS)
OISST Optimum Interpolation (OI) Sea Surface Temperature (SST) V2
RFI Radio Frequency Interference
SAC-D Satélite de Aplicaciones Científicas
SCA Single Channel Algorithm
SeaWiFS Sea-viewing Wide Field-of-view Sensor
SM Soil Moisture
SMOS Soil Moisture Ocean Salinity
SWE Snow Water Equivalent
TB Brightness Temperature
TOA Top Of Atmosphere
UTC Coordinated Universal Time
VH transmit Vertical, receive Horizontal)
VV transmit Vertical, receive Vertical)
VWC Vegetation Water Content

Document Creation Date

02 December 2013

Document Revision Date

03 June 2014

Document URL

http://nsidc.org/data/docs/daac/aquarius/aq2-sm/index.html