Deriving long-term time series of sea ice cover from satellite passive-microwave multisensor data sets

We have generated consistent sea ice extent and area data records spanning 18.2 years from passive-microwave radiances obtained with the Nimbus 7 scan ning multichannel microwave radiometer and with the Defense Meteorological Satellite Program F8, F11, and F13 special sensor microwave/imagers. The go al in the creation of these data was to produce a long-term, consistent set of sea ice extents and areas that provides the means for reliably determin ing sea ice variability over the 18.2-year period and also serves as a base line for future measurements. We describe the method used to match the sea ice extents and areas from these four multichannel sensors and summarize th e problems encountered when working with radiances from sensors having diff erent frequencies, different footprint sizes, different visit times, and di fferent calibrations. A major obstacle to adjusting for these differences i s the lack of a complete year of overlapping data from sequential sensors. Nonetheless, our procedure reduced ice extent differences during periods of sensor overlap to less than 0.05% and ice area differences to 0.6% or less .