. Application of enhanced resolution gridded passive microwave data for sea ice concentration and motion estimates

Abstract
A new passive microwave data set has been produced that has the potential to substantially improve estimates of sea ice concentration, motion, and other key parameters of interest. The gridded passive microwave brightness temperature product includes several improvements over the current source for sea ice geophysical retrievals. First, it uses the most-up-date source of input swath data with improved calibration and geolocation. Second, it grids the swath data onto the EASE-Grid 2.0 equal area projection, which facilitates easier area and transport calculations than the current polar stereographic projections. Finally, while it provides grids in standard spatial resolution (25 km), it also includes enhanced-resolution grids as fine as 3.125 km – an 8-fold improvement in resolution. The resolution enhancement approach is not a simple interpolation but rather a synthetic reconstruction of sensor footprints based on multiple overlapping footprints. Initial analysis indicates that a sharper sea ice edge can be obtained and there is the potential to yield smaller-scale features, such as leads and small polynyas within the sea ice cover and obtain more precise ice motion estimates. In addition, the enhanced-resolution fields are produced twice-daily local time. The “evening” and “morning” fields provide insights into diurnal effects on the ice cover and yield sub-daily motion information. Such short-term change is valuable in assessing the interaction of the ice cover with the atmosphere (e.g., estimation of heat fluxes from polynyas), and the ocean (e.g., salinity fluxes, new ice production). And if implemented in a near-real-time processing mode, could potentially improve sea ice forecasts. The enhanced-resolution passive microwave product will yield a 40+ year, high quality record with greater spatial and temporal resolution than is currently available. This will represent a substantial evolution from the current long-term sea ice climate records. This study has been funded by the CIRES Innovative Research Program.