NSIDC has discovered an issue with DMSP-F17 brightness temperature (Tb) values from the 37V channel - files from April 2016 through 01 January 2020 may have all 0 K or NaN Tvalues. We are working to resolve this issue and republish the data files as soon as possible. 
On Wednesday, July 8th between 9:00 am and 1:00 pm MDT, the following data collections may not be available due to planned system maintenance: AMSR-E, Aquarius, ASO, High Mountain Asia, IceBridge, ICESat/GLAS, ICESat-2, MEaSUREs, MODIS, NISE, SMAP, SnowEx, and VIIRS. 
Data Set ID:
NSIDC-0630

MEaSUREs Calibrated Enhanced-Resolution Passive Microwave Daily EASE-Grid 2.0 Brightness Temperature ESDR, Version 1

This data set, part of the NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) program, is an improved, enhanced-resolution, gridded passive microwave Earth System Data Record (ESDR) for monitoring cryospheric and hydrologic time series from SMMR, SSM/I-SSMIS, and AMSR-E. It is derived from the most mature and available Level-2 satellite passive microwave records from 1978 through the present.

This is the most recent version of these data.

Version Summary:

Initial release

COMPREHENSIVE Level of Service

Data: Data integrity and usability verified; data customization services available for select data

Documentation: Key metadata and comprehensive user guide available

User Support: Assistance with data access and usage; guidance on use of data in tools and data customization services

See All Level of Service Details

Parameter(s):
  • MICROWAVE > BRIGHTNESS TEMPERATURE
Data Format(s):
  • NetCDF
Spatial Coverage:
N: 90, 
S: -90, 
E: 180, 
W: -180
Platform(s):Aqua, DMSP 5D-2/F10, DMSP 5D-2/F11, DMSP 5D-2/F13, DMSP 5D-2/F14, DMSP 5D-2/F8, DMSP 5D-3/F15, DMSP 5D-3/F16, DMSP 5D-3/F17, DMSP 5D-3/F18, DMSP 5D-3/F19, Nimbus-7
Spatial Resolution:
  • 3.125 km to 25 km
Sensor(s):AMSR-E, SMMR, SSM/I, SSMIS
Temporal Coverage:
  • 25 October 1978 to 31 December 2019
(Updated 2020)
Version(s):V1
Temporal Resolution12 hourMetadata XML:View Metadata Record
Data Contributor(s):Mary Brodzik, David Long, Molly Hardman, Aaron Paget, Richard Armstrong

Geographic Coverage

Other Access Options

Other Access Options

Close

As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

Brodzik, M. J., D. G. Long, M. A. Hardman, A. Paget, and R. Armstrong. 2016, Updated 2020. MEaSUREs Calibrated Enhanced-Resolution Passive Microwave Daily EASE-Grid 2.0 Brightness Temperature ESDR, Version 1. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: https://doi.org/10.5067/MEASURES/CRYOSPHERE/NSIDC-0630.001. [Date Accessed].
Created: 
5 March 2020
Last modified: 
26 May 2020

Data Description

The Calibrated Enhanced Resolution Brightness Temperature (CETB) data set consists of gridded passive microwave brightness temperature data from the following instruments:

The data are a new, multi-sensor Level 3 Earth Science Data Record (ESDR) with recently released improvements in cross-sensor calibration and quality checking, modern file formats, better quality control, improved projection grids, and local time-of-day (LTOD) processing. These data are gridded to the EASE-Grid 2.0 definition and include enhanced-resolution imagery, as well as coarse-resolution, averaged imagery.

Parameters

The parameters for this data set are listed in Table 1.

Parameter Description Fill Value Missing Value
Table 1. Parameters
TB Brightness temperature 0.0 600.00
TB_time Average time of the measurements used to derive TB -32768 Not used
TB_std_dev Standard deviation of the measurements used to derive TB 655.35 655.34 (only used when TB is set to missing value)
TB_num_samples Number of measurements used to derive TB 0 Not used
Incidence_angle Average incidence angle of the measurements used to derive TB -0.01 (°) Not used

File Information

Format

The data are in netCDF (.nc) format, using CF 1.6 (Climate and Forecast) and ACDD 1.3 (Attribute Conventions for Dataset Discovery) metadata conventions.

Individual CETB file sizes range from 0.08 MB to 102.6 MB. File sizes vary because CETB files employ internal compression. A full day of data ranges in size from 13.06 MB to 9.79 GB, with an average of 3.94 GB per day.

Directory Structure

Files are stored here: https://n5eil01u.ecs.nsidc.org/MEASURES/NSIDC-0630.001/. This directory organizes files by the date of the earliest data in them. All Temperate grids produce data from 00:00 to 23:59.99, so all data correspond exactly to the date of file. Northern and Southern grids produce data that may include data from up to 6 hours of the day before and possibly the day after. These files are placed in the directory that matches the beginning of the data in the file, not the date of the file itself.

Example: Input data for a file from day X starts a couple hours prior to midnight UTC day X. This file will be in the directory for day X-1, and there will be no file in directory for day X.

Note: this issue does not affect users who access the data through EarthData Search.

File Contents

Figure 1 contains example NetCDF data from 9 October 2013. All parameters listed in Table 1 are included, in addition to x (projected coordinate), y (projected coordinate), and time (days since 01 January 1970) variables.

Figure 1. Sample NetCDF data from file NSIDC-0630-EASE2_N25km-F15_SSMI-2013282-19H-E-GRD-CSU-v1.3.nc. The data file contains the 19 GHz H-polarized measurements at the 25 km Northern Hemisphere resolution. 

Figures 2-4 are examples of AMSR-E data from 27 September 2011. There is one image per grid (Southern, Temperate & Tropical, and Northern). The Northern and Southern images have a spatial resolution of 3.125 km, while the Temperate & Tropical image has a resolution of 6.25 km.

Figure 2. Northern Hemisphere sample image from file NSIDC-0630-EASE2_N3.125km-AQUA_AMSRE-2011270-36H-M-SIR-RSS-v1.3.nc. The image shows 36 GHz H-polarized TB (in Kelvin) at 3.125 km Enhanced Resolution; TB was derived using the rSIR method.
Figure 3. Temperate grid sample image from file NSIDC-0630-EASE2_T6.25km-AQUA_AMSRE-2011270-18H-A-SIR-RSS-v1.3.nc. The image shows 18 GHz H-polarized TB (in Kelvin) at 6.25 km Enhanced Resolution; TB was derived using the rSIR method.
Figure 4. Southern Hemisphere sample image from file NSIDC-0630-EASE2_S3.125km-AQUA_AMSRE-2011270-36H-M-SIR-RSS-v1.3.nc. The image shows 36 GHz H-polarized TB (in Kelvin) at 3.125 km Enhanced Resolution; TB was derived using the rSIR method.

Naming Convention

Files are named according to the following convention and as described in Table 2:

NSIDC-0630-EASE2_GXXXXkm-platform_sensor-yyyyddd-channel-pass-algorithm-input-version.nc

Variable Description Values
Table 2. File Name Variables
NSIDC-0630 NSIDC unique data set identifier NSIDC-0630
EASE2_ EASE2-Grid 2.0 projection

EASE2
Grid =

GXXXXkm Grid and resolution of data in the file Grid = Northern (N), Southern (S), or Temperate & Tropical (T)
Resolution (in km) = ranges from 3.125 to 25 km
platform_sensor Satellite platform id and sensor NIMBUS7_SMMR
F08_SSMI
F10_SSMI
F11_SSMI
F13_SSMI
F14_SSMI
F15_SSMI
AQUA_AMSR-E
F16_SSMIS
F17_SSMIS
F18_SSMIS
F19_SSMIS
yyyyddd Reference day 4-digit year, 3-digit day of year
channel Channel ID = 2-digit frequency and 1-letter polarization (horizontal (H) or vertical (V)) Differs by sensor, e.g. 37H
pass The direction or LTOD of the satellite passes used 1-letter code:
A = Ascending (T grids only)
D = Descending (T grids only)
M = Morning LTOD (N or S grids only)
E = Evening LTOD (N or S grids only)
algorithm Specifies the algorithm used for the image reconstruction GRD = drop-in-the-bucket (25 km grids)
SIR = radiometer version of Scatterometer Image Reconstruction (enhanced-resolution grids)
input Input data producer CSU = Colorado State University
RSS = Remote Sensing Systems
version Data set version number vX.X for major/minor versions (e.g. v1.3)
nc NetCDF data formatting suffix .nc
Example file name:

NSIDC-0630-EASE2_N3.125km-F08_SSMI-1987304-37H-M-SIR-RSS-v1.3.nc

Spatial Information

Coverage

Each data file contains one of three EASE-Grid 2.0 spatial coverages:

  • Northern Hemisphere Lambert azimuthal equal-area
  • Southern Hemisphere Lambert azimuthal equal-area
  • Temperate & Tropical cylindrical equal-area projection (bounded by +/- 67° latitude).

Spatial Resolution

Each channel is processed at standard and enhanced resolutions. The standard grid resolution is 25 km, with enhanced-resolution grids defined in a nested fashion in powers of two: 12.5 km, 6.25 km, and 3.125 km (see Figure 5). All channels are gridded to 25 km, with higher resolutions dependent on channel frequency:

  • Frequencies below 12 GHz are available at 25 km (standard) and 12.5 km (enhanced).
  • Frequencies between 12 and 30 GHz are available at 25 km (standard) and 6.25 km (enhanced).
  • Frequencies 30 GHz and above are available at 25 km (standard) and 3.125 km (enhanced).
Figure 5. EASE-Grid 2.0 nesting relationship for 25 km and 12.5 km azimuthal grids at the pole. All CETB grids are nested analogously.

Geolocation

The following tables provide information for geolocating this data set. The data are gridded to EASE-Grid 2.0 projections, at various coverages and spatial resolutions, as defined in Table 2. For more details on EASE-Grid 2.0, please refer to the EASE Grids web pages.

Name Projection Resolution (km) Columns Rows

Latitude Extent (degrees)

Longitude Extent (degrees)
Table 3. CETB EASE-Grid 2.0 Projections and Grid Dimensions
EASE2_N25km Northern Lambert Azimuthal 25 720 720 0 - 90 -180 - 180
EASE2_N12.5km Northern Lambert Azimuthal 12.5 1440 1440 0 - 90 -180 - 180
EASE2_N6.25km Northern Lambert Azimuthal 6.25 2880 2880 0 - 90 -180 - 180
EASE2_N3.125km Northern Lambert Azimuthal 3.125 5760 5760 0 - 90 -180 - 180
EASE2_S25km Southern Lambert Azimuthal 25 720 720 -90 - 0 -180 - 180
EASE2_S12.5km Southern Lambert Azimuthal 12.5 1440 1440 -90 - 0 -180 - 180
EASE2_S6.25km Southern Lambert Azimuthal 6.25 2880 2880 -90 - 0 -180 - 180
EASE2_S3.125km Southern Lambert Azimuthal 3.125 5760 5760 -90 - 0 -180 - 180
EASE2_T25km Cylindrical Equal-Area 25.02526 1388 540 +/-67.0575406 -180 - 180
EASE2_T12.5km Cylindrical Equal-Area 12.51263 2776 1080 +/-67.0575406 -180 - 180
EASE2_T6.25km Cylindrical Equal-Area 6.256315 5552 2160 +/-67.0575406 -180 - 180
EASE2_T3.125km Cylindrical Equal-Area 3.128.15750 11104 4320 +/-67.0575406 -180 - 180

Temporal Information

Coverage

Temporal coverage varies by sensor. See Table 4 for the actual coverages.

Sensor Platform Begin Coverage End Coverage *
Table 4. Temporal Coverage by Sensor
AMSR-E AQUA 01 June 2002 04 October 2011
SSM/I F08
F10
F11
F13
F14
F15
07 September 1987
08 December 1990
03 December 1991
03 May 1995
07 May 1997
23 February 2000
31 December 1991
14 November 1997
16 May 2000
19 November 2009
23 August 2008
31 December 2019
SSMIS F16
F17
F18
F19
01 November 2005
01 March 2008
08 March 2010
27 November 2014
31 December 2019
31 December 2019
31 December 2019
09 February 2016
SMMR Nimbus 25 October 1978 20 August 1987

*End coverage represents the end date for the majority of the granules.

Resolution

The grids are produced twice daily. Temperate grids are separated by ascending/descending passes, while the Northern and Southern grids are separated by local time of day (LTOD).

Table 4 shows the beginning and ending times for the LTOD morning/evening split in hours after UTC midnight on the day of processing. Note also that for all platforms except AMSR-E, the LTOD split times are the same for the Northern and Southern hemispheres. All of the Northern and Southern grids in the data set were processed with these times. These values are stored as part of the metadata in the CETB files as an attribute of the TB data.

Table 5. LTOD Times
Platform Year Morning start time Morning end time Evening start time Evening end time
F08 All years 0.0 12.0 12.0 24.0
F10 1990-1993 2.0 14.0 14.0 26.0
F10 1994 3.0 15.0 15.0 27.0
F10 1995-1997 4.0 16.0 16.0 28.0
F11 All years 0.0 12.0 12.0 24.0
F13 All years 0.0 12.0 12.0 24.0
F14 1997-2001 3.0 15.0 15.0 27.0
F14 2002-2004 2.0 14.0 14.0 26.0
F14 2005-2008 0.0 12.0 12.0 24.0
F15 2000-2005 3.0 15.0 15.0 27.0
F15 2006-2007 2.0 14.0 14.0 26.0
F15 2008-2011 0.0 12.0 12.0 24.0
F15 2012 -2.0 10.0 10.0 22.0
F15 2013-2016 -3.0 09.0 9.0 21.0
F16 2005-2007 3.0 15.0 15.0 27.0
F16 2008-2009 2.0 14.0 14.0 26.0
F16 2010-2011 1.0 13.0 13.0 25.0
F16 2012-2013 0.0 12.0 12.0 24.0
F16 2014 -1.0 11.0 11.0 23.0
F16 2015-2017 -2.0 10.0 10.0 22.0
F17 All years 0.0 12.0 12.0 24.0
F18 All years 0.0 12.0 12.0 24.0
F19 All years 0.0 12.0 12.0 24.0
SMMR All years 6.0 18.0 18.0 30.0
AMSR-E All years NH 5.0 17.0 17.0 29.0
AMSR-E All years SH 8.0 20.0 20.0 32.0

Data Acquisition and Processing

Background

The following sections describe CETB gridding algorithms. Please refer to Long and Brodzik (2016) for the theory of reconstruction techniques and complete details of the radiometer form of the Scatterometer Image Reconstruction (rSIR). The algorithm theoretical basis document (ATBD) for this data product (Brodzik and Long, 2018) also contains more details.

Coarse Resolution (GRD) Gridding Algorithms
The CETB standard resolution gridding procedure is a simple, “drop-in-the-bucket” average. The resulting data grids are designated GRD data arrays. For the "drop-in-the-bucket" gridding algorithm, the key information required is the location of the measurement. The center of each measurement geolocation is mapped to an output-projected grid cell. All measurements within the specified time period that fall within the bounds of a particular grid cell are averaged. This is the reported TB value for this pixel. Ancillary variables contain the number and standard deviation of included samples. The effective spatial resolution of the GRD product is defined by a combination of the pixel size and spatial extent of the 3dB antenna footprint size. Figure 6 provides a graphical representation of the standard resolution (25 km) of GRD measurements.

Figure 6. GRD 25 km Resolution

The radiometer version of the Scatterometer Image Reconstruction (rSIR) Algorithm
In addition the standard GRD resolution (25 km), all channels are also available at one nested, enhanced resolution (12.5 km, 6.25 km, or 3.125 km); see Table 6 for more details. Enhanced resolutions are generated using the radiometer version of the Scatterometer Image Reconstruction (rSIR) algorithm. The rSIR algorithm defines a group of pixels centered at each grid point. Each pixel is then weighted based on the Measurement Response Function (MRF) to estimate the TB at the enhanced resolution footprint. The MRF is determined by the antenna gain pattern (which is unique for each sensor and sensor channel, and may vary with scan angle), the scan geometry (notably the antenna scan angle), and the integration period. Figure 6 provides a graphical representation of the enhanced resolution of rSIR measurements. For a more details, see Long and Brodzik (2016) or Brodzik and Long (2018).

Figure 7. rSIR 3.125 km Resolution

Sensor Frequency (GHz) Enhanced Resolution Grid (km)
12.5 6.25 3.125
Table 6. CETB Enhanced Resolution Grids
SMMR 6 X
SMMR 10 X
SMMR 18 X
SMMR 21 X
SMMR 37 X
SSM/I 19 X
SSM/I 22 X
SSM/I 37 X
SSM/I 85 X
SSMIS 19 X
SSMIS 22 X
SSMIS 37 X
SSMIS 91 X
AMSR-E 6 X
AMSR-E 10.7 X
AMSR-E 18 X
AMSR-E 23 X
AMSR-E 36 X
AMSR-E 89 X

Acquisition

Table 7 lists all input data sets.

Sensor Temporal Coverage Input Swath Data
Table 7. Input Data Sources
SMMR 1978-1987 Nimbus-7 SMMR Pathfinder Brightness Temperatures, Version 1 (NSIDC-0036)
SSM/I-SSMIS 1987-2017 CSU FCDR (http://rain.atmos.colostate.edu/FCDR/)
AMSR-E 2002-2011 AMSR-E/Aqua L2A Global Swath Spatially-Resampled Brightness Temperatures, Version 3 (AE_L2A)

Processing

There are two general processing steps in generating the CETB product. These include data set pre-processing for spatial and temporal selection and gridding (both standard and enhanced resolutions).

1. Data set preprocessing
The first stage of processing includes ingesting the raw swath TB and performing initial data and temporal selections. Only the highest quality TB measurements are used to ensure the most reliable data set. Swath data are mapped to output grids by measurement geolocation and LTOD.

All of the CETB passive microwave sensors fly on near-polar, sun-synchronous satellites, which maintain an orbital plane with an orientation that is (approximately) fixed with respect to the sun. Thus, the satellite crosses the equator on its ascending (northbound) path at approximately the same LTOD. The resulting coverage pattern yields passes about 12 hours apart in LTOD at the equator. Most areas near the pole are covered multiple times per day. Analysis shows that the data from a single sensor fall into two LTOD ranges for polar measurements. The two periods are typically less than 4 hours long and spaced 8 or 12 hours apart. Significantly, due to the orbit repeat cycle, two succeeding days at any particular location may make measurements at different LTOD, and therefore, at different times during the diurnal cycle (Gunn, 2007), introducing undesired variability (noise) into a time series analysis.

The CETB azimuthal (Northern or Southern) grids are split into two images per day based on the LTOD approach of Gunn and Long (2008). This ensures that all measurements in any one image have consistent spatial/temporal relationships. The CETB adopts the LTOD division scheme for the Northern and Southern hemispheres. For the Temperate grids the data are divided into ascending and descending passes.

Each file includes gridded arrays of the following variables: TB, number of contributing measurements, as well as the average time, standard deviation, and average incidence angle of contributing measurements used to derive the TB at each pixel. This enables investigators to explicitly account for the LTOD temporal variation of the measurements included in a particular pixel.

2. Gridding

CETB products are generated on standard resolution grids for all channels using a low-noise “drop-in-the-bucket” average (GRD algorithm), and enhanced-resolution grids using rSIR image reconstruction techniques (Long and Brodzik, 2016). For enhanced-resolution grids, the effective resolution depends on the number of measurements and the precise details of their overlap, orientation, and spatial locations; information about the antenna gain pattern, scan geometry, and integration period are required to compute the effective measurement response function (MRF). The MRF describes how much the emissions from a particular direction affect the observed TB value. For each sensor and channel, the MRF is modeled as a two-dimensional Gaussian using the 3-dB footprint size (Long and Brodzik, 2016). See Table 8 for the field-of-view values.

Sensor Frequency (GHz) Semi-major (km) Semi-minor (km)
Table 8. Effective Field of View
SSMI 19 H, V 69 43
SSMI 22 V 60 40
SSMI 37 V 37 28
SSMI 37 H 37 29
SSMI 85 H, V 15 13
SSMIS 19 H, V 72 44
SSMIS 22 V 72 44
SSMIS 37 H, V 44 26
SSMIS 91 H, V 15 9
AMSR-E 6 H, V 75 43
AMSR-E 10.7 H, V 51 29
AMSR-E 18 H, V 27 16
AMSR-E 23 H, V 32 18
AMSR-E 36 H, V 14 8
AMSR-E 89 (H or V) 7 4
AMSR-E 89 (H or V) 6 4
SMMR 6.6 H, V 121 79
SMMR 10.7 H, V 74 49
SMMR 18 H, V 44 29
SMMR 21 H, V 38 24
SMMR 37 H, V 21 14

Quality, Errors, and Limitations

Earlier Versions

Version 1.3 renders all previous versions of this data set obsolete; users should update their files accordingly. The Version 1.3 release included a reprocessing of all data to implement the improvements described in the Appendix of this document.

Empty pixels in GRD images
In cases where no swath measurement center locations were mapped to the area of a gridded pixel, GRD images will occasionally have single pixels with no data. Normally, rSIR images do not suffer from this problem, because the rSIR gain threshold is set to a value that almost always ensures at least one component measurement that can be used to derive the pixel TB. However, beginning on 04 Nov 2004, the AMSR-E 89 GHz A-horn developed a permanent problem that resulted in a loss of observations for the remaining life of AMSR-E. After this date, the rSIR 3.125 km 89 GHz data does occasionally have missing pixels (Beitsch et al., 2014).

Missing Dates
There are files to match every day of a sensor's temporal coverage. For dates with no data, data files exist with all variables set to "_FillValue."

Incomplete Image Reconstruction at Latitudinal Grid Boundaries
Not all possible input measurements were used in the image reconstruction at the high-latitude edges of the Temperate grids and at the equatorial edges of the Northern and Southern grids. Although the reconstructed TB at these locations are not erroneous, they are not as accurate as the reconstructed TB that make use of all input measurements.

The user is encouraged to exercise caution when analyzing data within approximately 20 km of these boundaries. To access the most accurate image reconstruction results, the user is advised to use the Northern or Southern grids to analyze mid- to high-latitude regions, and the Temperate grids to analyze regions near the equator. For example, when analyzing CETB 6.25 km rSIR Temperate images, switch to the Northern grid to analyze images within 3 pixels of the northern boundary. Analogously, when analyzing CETB 6.25 km rSIR Northern images, switch to the Temperate grid to analyze images within 3 pixels of the equator.

Note: the eastern and western boundaries of the Temperate grids (i.e., 180º E and 180º W) do not exhibit this problem, as all input measurements were included in the image reconstruction at these locations.

Quality
For a comparison to other passive microwave data sets, please see the Algorithm Theoretical Basis Document (Brodzik and Long 2018).

Instrumentation

Description

For a detailed description of the instruments used to acquire the data, see the following NSIDC websites:

Table 10 provides a list of the channels for each instrument. All channels are gridded to 25 km, with higher resolutions depend on channel frequency:

  • Frequencies below 12 GHz are available at 25 km (standard) and 12.5 km (enhanced).
  • Frequencies between 12 and 30 GHz are available at 25 km (standard) and 6.25 km (enhanced).
  • Frequencies 30 GHz and above are available at 25 km (standard) and 3.125 km (enhanced).
Sensor Channel Frequency (GHz) and Polarization
Table 10. CETB Product Sensors and Channels
SMMR 6H, 6V, 10H, 10V, 18H, 18V, 21H, 21V, 37H, 37V
SSM/I 19H, 19V, 22V, 37H, 37V, 85H, 85V
SSMIS 19H, 19V, 22V, 37H, 37V, 91H, 91V
AMSR-E 6H, 6V, 10.7H, 10.7V, 18H, 18V, 23H, 23V, 36H, 36V, 89H, 89V

Software and Tools

For a list of resources for accessing NetCDF files, see the NSIDC NetCDF Software Tools website. Geolocation files for this data set are in netCDF (.nc) format and are located here: ftp://sidads.colorado.edu/pub/tools/easegrid2/. File names indicate the grids for each file: Northern (N), Southern (S), or Temperate & Tropical (T). For example, EASE2_N12.5km.geolocation.v0.9.nc corresponds to the 12.5 km resolution grid in the Northern Hemisphere.

Version History

Table 11 lists the version history for this data set.

Table 11. Version History
Version
Date Published
Description of Changes
1.4
26 May 2020
Temporal update through 30 December 2019 for data derived from the SSM/I DMSP-F-15 sensor and the SSMIS DMSP-F16, -F17, and -F18 sensors.
File-level metadata updated to acknowledge new funding sources and reflect changes to the data citation.
1.3
14 June 2018
See the Appendix – Corrections made to Version 1.3 for details
1.2
26 September 2017
For the AMSR-E-derived data, changes include:
  • Adding missing input data for the first day of the month in the Northern Hemisphere and Southern Hemisphere projections
  • Changing the size of the time dimension from 1 to "UNLIMITED"
  • Adding files for dates with no data
For SSMI-derived data, corrected the handling of QC flags to retain more data, eliminating only the flagged data in a given channel and taking care not to eliminate data in other channels
Includes data derived from the following additional sensors:
  • SSM/I on DMSP-F15
  • SSMIS on DMSP-F16
  • SSMIS on DMSP-F17
  • SSMIS on DMSP-F18
  • SSMIS on DMSP-F19
  • SMMR on Nimbus
1.1
03 May 2017
First public release.
Includes data derived from the following additional sensors:
  • SSM/I on DMSP-F08
  • SSM/I on DMSP-F10
  • SSM/I on DMSP-F11
  • SSM/I on DMSP-F13
  • SSM/I on DMSP-F14
1.0
December 2016
Internal release, only contained AMSR-E-derived data

Related Data Sets

Related Websites

NASA MEaSUREs Research Project: EASE-Grid 2.0 TB ESDR

Scatterometer Climate Record Pathfinder

Contacts and Acknowledgments

Mary J. Brodzik
National Snow and Ice Data Center
449 UCB, 1540 30th St.
Boulder, CO 80309

David Long
Brigham Young University
Microwave Earth Remote Sensing (MERS) Laboratory
459 CB
Provo, UT 84602

Molly Hardman
National Snow and Ice Data Center
449 UCB, 1540 30th St.
Boulder, CO 80309

Aaron Paget
Brigham Young University
Microwave Earth Remote Sensing (MERS) Laboratory
459 CB
Provo, UT 84602

Richard Armstrong
National Snow and Ice Data Center
449 UCB, 1540 30th St.
Boulder, CO 80309

References

Beitsch, A., L. Kaleschke, and S. Kern. 2014. Investigating High-Resolution AMSR2 Sea Ice Concentrations during the February 2013 Fracture Event in the Beaufort Sea. Remote Sensing 6(5): 3841-3856. doi: http://dx.doi.org/10.3390/rs6053841

Brodzik, M. J. and Long, D. G. 2018. Calibrated Passive Microwave Daily EASE-Grid 2.0 Brightness Temperature ESDR (CETB) Algorithm Theoretical Basis Document [PDF file]. Retrieved from: https://nsidc.org/sites/nsidc.org/files/technical-references/MEaSUREs_CETB_ATBD_v1.0.pdf

Gunn B. 2007. Temporal resolution enhancement for AMSR images. BYU Internal Report MERS 07-002. http://www.mers.byu.edu/docs/reports/MERS0702.pdf

Gunn B. A. and D. G. Long. 2008. Spatial resolution enhancement of AMSR TB images based on measurement local time of day. In IGARSS 2008-2008 IEEE International Geoscience and Remote Sensing Symposium, vol. 5, pp. V-33. IEEE. doi: http://dx.doi.org/10.1109/IGARSS.2008.4780020

Long, D. G. and M. J. Brodzik. 2016. Optimum Image Formation for Spaceborne Microwave Radiometer Products. IEEE Transactions on Geoscience and Remote Sensing 54(5): 2763-2779. doi: http://dx.doi.org/10.1109/TGRS.2015.2505677

Appendix – Corrections made to Version 1.3

Version 1.3 renders all previous versions of this data set obsolete; users should update their files accordingly. The Version 1.3 release included a reprocessing of all data to implement the improvements described below:

Correction #1. Some morning grids were incorrectly classified as Evening data and vice-versa. For example, Morning passes for day N were mislabeled as Evening passes for day N-1. All Morning/Evening classifications for the Northern and Southern grids are correct starting with Version 1.3.

Correction #2. Adjusted 85, 89, and 91 GHz channel gain thresholds. All the data from the affected channels were originally processed with a gain threshold of 8 dB resulting in an excess of missing pixels. The threshold was adjusted to 12 dB in Version 1.3 to minimize missing pixels.

Correction #3. Originally Temperate grid processing did not include the final orbit from the prior calendar day, which may have included data from current day at the end of the swath. At worse, this would have eliminated up to 34 minutes of data at the beginning of the day; in most cases, it was much less than that. Temperate grid processing now includes all data from the beginning of the intended calendar day.

Correction #4. All Northern and Southern grid data were correctly processed into LTOD Morning and Evening divisions using the values in Table A1, but were reported incorrectly in the metadata. The error occurred only for split times that were different from 0.0-12.0-12.0-24.0. Where the errors occur, they were for the start time in the morning grids and for the end time in the evening grids. In each case the incorrect value was set to 0.0. For example, if the LTOD split times were 0300 and 1500, then the morning start time was incorrectly reported as 0.0 and the end time was correctly reported as 15.0. Similarly, the evening start time was correctly reported as 15.0 and the evening end time was incorrectly reported as 0.0. The affected metadata fields are:

  • TB:temporal_division_local_start_time for M (morning) files in the N or S projections
  • TB:temporal_division_local_end_time for E (evening) files in the N or S projections

Beginning in Version 1.3, all LTOD for the Northern and Southern grid data are correctly reported in the metadata.

Table A1. LTOD Crossing Times
Platform
Year
Morning start time
Morning end time
Evening start time
Evening end time
F08
All years
0.0
12.0
12.0
24.0
F10
1990-1993
2.0
14.0
14.0
26.0
F10
1994
3.0
15.0
15.0
27.0
F10
1995-1997
4.0
16.0
16.0
28.0
F11
All years
0.0
12.0
12.0
24.0
F13
All years
0.0
12.0
12.0
24.0
F14
1997-2001
3.0
15.0
15.0
27.0
F14
2002-2004
2.0
14.0
14.0
26.0
F14
2005-2008
0.0
12.0
12.0
24.0
F15
2000-2005
3.0
15.0
15.0
27.0
F15
2006-2007
2.0
14.0
14.0
26.0
F15
2008-2011
0.0
12.0
12.0
24.0
F15
2012
-2.0
10.0
10.0
22.0
F15
2013-2016
-3.0
09.0
9.0
21.0
F16
2005-2007
3.0
15.0
15.0
27.0
F16
2008-2009
2.0
14.0
14.0
26.0
F16
2010-2011
1.0
13.0
13.0
25.0
F16
2012-2013
0.0
12.0
12.0
24.0
F16
2014
-1.0
11.0
11.0
23.0
F16
2015-2017
-2.0
10.0
10.0
22.0
F17
All years
0.0
12.0
12.0
24.0
F18
All years
0.0
12.0
12.0
24.0
F19
All years
0.0
12.0
12.0
24.0
SMMR
All years
6.0
18.0
18.0
30.0
AMSR-E
All years NH
-5.0
7.0
7.0
19.0
AMSR-E
All years SH
-4.0
8.0
8.0
20.0

Correction #5. At calendar year crossovers, data from the prior year (Dec 31) were not included in Jan 1 data, and data from the following year (Jan 1) were not included in Dec 31 data. Version 1.3 corrected this processing so that calendar year crossovers include data from Dec 31 and Jan 1, respectively.

Correction #6. Under rare, but not impossible conditions, occasional ascending scanlines were incorrectly classified as descending, and vice-versa. These incorrect classifications were fixed beginning with Version 1.3.

Correction #7. Prior to Version 1.3, static LTOD split times were used for the duration of the F16 record, but orbital drift required changing split times. LTOD split times became progressively more offset over the lifetime of the sensor, so that the static LTOD split times were eventually off by 5 hours, resulting in morning data being incorrectly classified as evening data and vice-versa. LTOD shifts due to orbital drift were corrected starting with Version 1.3.

Correction #8. Version 1.3 corrected the split times for the Northern grids, which were off by 2 hours. This correction only applied to AMSR-E-derived data.

How To

Programmatic Data Access Guide
Data from the NASA National Snow and Ice Data Center Distributed Active Archive Center (NSIDC DAAC) can be accessed directly from our HTTPS file system or through our Application Programming Interface (API). Our API offers you the ability to order data using specific temporal and spatial filters... read more
Filter and order from a data set web page
Many NSIDC data set web pages provide the ability to search and filter data with spatial and temporal contstraints using a map-based interface. This article outlines how to order NSIDC DAAC data using advanced searching and filtering.  Step 1: Go to a data set web page This article will use the... read more

FAQ