Introduction

A task fundamental to advancing global change research is the availability of a standard reference system for direct digital comparison and interuse of remote sensing data sets on varying spatial and temporal scales. The Equal-Area Scalable Earth Grid (EASE-Grid) is a standard gridding scheme now used with a variety of satellite datasets, including Special Sensor Microwave/Imager (SSM/I) data. We developed software which allows users of SSM/I data to produce their own EASE-Grid image data from Temperature Data Record (TDR) format swath data. The EASE-Grid's array format facilitates data storage, retrieval, and display, and is essential to time series studies and image subtraction. At Right: North polar EASE-Grid projection derived from 19Ghz SSM/I satellite observations.

Data

Software

The software allows users of SSM/I data to select and process temporal and spatial subsets of 19, 22 and 37 GHz swath data into the NSIDC EASE-Grid, using Backus-Gilbert optimal resampling. The EASE-Grid data are easier to use than swath format data, but still maximize the radiometric integrity of the original brightness temperatures, provide high spatial and temporal precision, and involve no averaging of original swath data. The EASE-Grid's array format facilitates data storage, retrieval, and display, and is essential to time series studies and image subtraction.

The new software is modular and currently incorporates the actual NSIDC EASE-Grid core modules. These are replaceable to simplify testing of alternative resampling and/or gridding algorithms. Temperature Data Record-format SSM/I data ingest for F-11 and F-13 is currently automated.

In addition, the new tools allow "full coverage" processing of data near the poles, in which overlapping swath data are separately retained for the highest possible temporal resolution (e.g., typically 4-6 observations for a given grid cell at 69 degrees latitude per day per SSM/I).

Distance-to-fixed-site and sensor-look-direction computations can be performed on swath data, and geographic subsetting can be performed before and/or after EASE-Gridding. When the NSIDC core modules are used, the output format is fully compatible with the IDL image display routines and tools supplied on the NSIDC EASE-Grid SSM/I Pathfinder CDROMs.

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