The SMMR channels were mapped to the SSM/I grid using a "drop-in-bucket" method. Empty grid elements (except those in the SMMR swath gaps equatorwards of 72 degrees) were filled by interpolation for all except the 10 GHz channels. The following paragraph from sec. 2.2.3, p. 24 of Gloersen et al. (1992) is reproduced here to provide further information about the gridding process. Note that this is not the same mapping method as is used for SSM/I, where multiple passes are averaged.
It should be noted that the number of observations represented in a given grid element in the present projection depends on latitude. The latitude bands completely covered by the SMMR during the course of 1 day are only 72 -84 N and 72 -84 S. Diamond-shaped data gaps occur on the 1-day maps equatorwards of 72 ; near the equator almost all of the data are updated twice every 6 calendar days. In the monthly aver-ages shown in Chapters 3 and 4, and Appendix A [of Gloersen et al. 1992], the data gaps are filled in as a result of the longer averaging period. Polewards of 72 , there is increasing overlap in the SMMR orbital swaths in which data were collected. Rather than averaging the data acquired in the overlap areas, the separate northbound and southbound data used for a given location are the values from the last observation of the individual day. The northbound and southbound values are averaged to produce single-day maps used for generating the monthly maps and time series plots in Chapters 3-5 of Gloersen et al. 1992.
Sea Ice Concentrations on SMMR CD-ROM Volume 7
CD-ROM Volume 7 contains sea ice concentration grids for the North and South polar regions derived from the SMMR brightness temperatures on CD-ROM Volumes 1-12. Volume 7 also contains North polar brightness temperatures for 1 April to 20 August 1987. North polar ice concentrations on Volume 7 are total ice, i.e., first year + multiyear. South polar ice concentrations are total ice, i.e., Type A + Type B.*