Moving towards an intercalibrated and homogenized SSM/I period of record

The Defense Meteorological Satellite Program Special Sensor Microwave Imager (SSM/I) is a seven-channel, four-frequency, orthogonally polarized, passive microwave radiometric system that measures atmospheric, ocean and terrain microwave brightness temperatures at 19.35, 22.2, 37.0, and 85.5 GHz. The National Oceanic and Atmospheric Administration's (NOAA) National Climatic Data Center (NCDC) archives and distributes SSM/I data collected from July 1987 to present. Passive microwave satellite measurements from SSM/I are reprocessed at NCDC and stored as network Common Data Form (netCDF) three-hourly files. In addition to reformatting the data, a normalized anomaly (z-score) for each footprint temperature value is calculated by subtracting each radiance value with the corresponding monthly one degree grid climatological mean and dividing it by the associated climatological standard deviation. Threshold checks are used to detect radiance, temporal and geolocation values that are outside expected ranges. NCDC has also obtained Remote Sensing Systems (RSS) Version 6 SSM/I data (for public distribution with no restrictions) from July 1987 to present, which is an intercalibrated and homogenized SSM/I time series. These efforts represent a significant step toward preserving and increasing the data maturity level of the longest satellite passive microwave period of record.