History and Data Source

Though NSIDC no longer distributes the Nimbus-7 SMMR Polar Radiances and Arctic and Antarctic Sea Ice Concentrations data on CD-ROM, this documentation is retained for users who have previously acquired the data via CD-ROM. The following sections provide more information regarding these data on CD-ROM.

The Nimbus-7 SMMR Polar Radiances and Arctic and Antarctic Sea Ice Concentrations CD-ROM series (12 volumes) is the most extensive set of SMMR grids for the polar regions to be released to date. This third SMMR series presents the entire SMMR time series for North and South polar regions (brightness temperatures and derived sea ice concentrations) in a single-channel file format. The data source for this SMMR CD-ROM time series is the SMMR TCT tape data set.

The two earlier CD-ROM SMMR data sets were in different formats, had different data sources, and served different purposes. The first CD-ROM, Nimbus-7 SMMR Brightness Temperature Grids, Northern Hemisphere, Volume 1, was issued by NSIDC in 1989. The disc contained grids for 29 October 1978 to 31 January 1980, presented in files containing interleaved values from all channels. The data source was the time series described in Polar Microwave Brightness Temperatures From Nimbus-7 SMMR: Time Series of Daily and Monthly Maps From 1978 to 1987 (Comiso and Zwally 1989), which used the SMMR CELL tapes as input. In late 1990 the SMMR Polar Data Sampler CD-ROM was issued by Dr. P. Gloersen at NASA Goddard Space Flight Center, Oceans and Ice Branch. This disc presented SMMR data in both interleaved and single-channel grids, with information to guide users in voting for a preferred final file format for this "real" SMMR time series, then under development by Dr. Gloersen.

The resulting SMMR CD-ROM series, described in this User's Guide, provides the complete SMMR sensor time series brightness temperature and derived sea ice concentration data, gridded to the SSM/I polar stereographic grids for the North and South polar regions.

A Note on the Title of This CD-ROM Series

Please note that the terms "brightness temperatures" and "radiances" are used interchangeably to describe the microwave data presented on the SMMR CD-ROMs.