What are the differences between NSIDC-0032 and NSIDC-0630?

The main differences between the DMSP SSM/I-SSMIS Pathfinder Daily EASE-Grid Brightness Temperatures, Version 2 (NSIDC-0032) and the MEaSUREs Calibrated Enhanced-Resolution Passive Microwave Daily EASE-Grid 2.0 Brightness Temperature ESDR, Version 1 (NSIDC-0630) data sets are described in Table 1.

Table 1. Differences between NSIDC-0032 and NSIDC-0630

File FormatBinaryNetCDF-CF
Input SourceRSS SSMI/SSMIS dataCSU SSMI(S) Brightness Temperature data
ProjectionsNorthern Hemisphere
Southern Hemisphere
Northern Hemisphere
Southern Hemisphere
GridEASE-GridEASE-Grid 2.0
Resolutions25 km
12.5 km
25 km
12.5 km
6.25 km
3.125 km
Gridding MethodBackus-Gilbert (prior to DMSP-F17)
Inverse Distance Squared method (after DMSP-F17)
"Drop-in-the-Bucket" gridding algorithm (25 km grids only)
Radiometer version of the Scatterometer Image Reconstruction (rSIR) algorithm (12.5, 6.25, and 3.125 resolutions)
Available SatellitesUses inputs from one satellite at a time, except for short periods of sensor overlap:
  • DMSP-F8: 1987-1991
  • DMSP-F11: 1991-1995
  • DMSP-F13: 1995-2007
  • DMSP-F17: 2006-present

Uses all available satellites (see Table 2 for more details)

Daily Gridding DivisionAscending/descendingNorthern & Southern Hemisphere grids: morning/evening by local time of day (LTOD)
Temperate grids: ascending/descending
Diurnal Range in Each FileAscending/descending UTC dayTemperate grids: ascending/descending UTC day
Northern/Southern Hemisphere grids: satellite-dependent 12-hour blocks, centered on local time of day
Parameters Included in FileBrightness temperature (Tb)
Brightness temperature (Tb)
Number of observations
Standard deviation
Incidence angle

Table 2. Temporal coverage by sensor for NSIDC-0630


Begin Coverage
End Coverage
01 June 2002
04 October 2011
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
01 January 2020
01 November 2005
01 March 2008
08 March 2010
27 November 2014
01 January 2020
01 January 2020
01 January 2020
09 February 2016
25 October 1978
20 August 1987

Other important differences

One of the biggest differences between NSIDC-0032 and NSIDC-0630 is how they divide input data.

  • NSIDC-0032 divides input data into ascending/descending swaths.
  • NSIDC-0630 divides input data into morning/evening files based on the local time of day of measurements.

This means that some input swaths with a UTC time from the previous day may be incorporated into morning files, and some input files with a UTC time from the following day may be incorporated into evening files. The image below demonstrates how this swath division affects an average day in a Northern Hemisphere 25 km grid. A more complete description of how NSIDC-0630 divides input swaths is captured in the NSIDC-0630 user guide.

Data image: Division of input data swaths for March 5, 2015
Data image: Division of input data swaths for March 5, 2015. Figure a) shows the morning swath, with input data from UTC Day March 4, 2015 and March 5, 2015. Figure b) shows the evening swath, with input files from UTC day March 5, 2015 and March 6, 2015.

In addition to dividing input files different, NSIDC-0032 and NSIDC-0630 also interpret input file quality flags differently. Compared to NSIDC-0032, NSIDC-0630 requires a higher quality threshold in order to calculate Tb values from input data. This threshold particular impacts the DMPS-F17 37V channel; after April 2016, Tb from this instrument and channel may have all 0 K or NaN values.

Lastly, the figure below demonstrates how different input files and production processes create unique brightness temperature profiles in NSIDC-0032 and NSIDC-0630. As the small figures in the upper left-hand corners of plot a and b show, the data sets correlate best where they draw from the same UTC day and deviate more dramatically where NSIDC-0630 uses input data from a different UTC day.

Data image: Comparisons of NSIDC-0630 and NSIDC-0032 brightness temperature values
Data image: Comparisons of NSIDC-0630 and NSIDC-0032 brightness temperature values from a) the 5 March 2015 North Hemisphere 25 km 19H files and b) the 5 March 2015 Southern Hemisphere 25 km 37V files. The figure inset in the upper left-hand corner of each chart shows where the two data sets differ most across the Northern Hemisphere. In the inset, red colors indicated NSIDC-0630 TB are > NSIDC-0032 TB estimates, blue colors indicate NSIDC-0630 TB are < NSIDC-0032 TB estimates, and white areas indicate no difference between the two data sets; the brightest red corresponding to +100 K, the brightest blue correspond to -100 K.