The DMSP-F13 SSMI Rain Rate Over Oceans layer indicates the rain rate in millimeters per hour (mm/hr) over oceans. The imagery resolution is about 0.25 degrees, or about 28 kilometers, and the temporal resolution is daily. This is available in two layers, ascending, local PM and descending, local AM. This layer was constructed by the Special Sensor Microwave/Imager (SSM/I) sensor that flew on the Defense Meteorological Satellite Program (DMSP) F13 spacecraft using a unified, physically based algorithm to retrieve rain rate measurements.

The F13 spacecraft is flown by the DMSP on the two operational polar orbiting platforms and had an orbit that was near-circular, sun-synchronous, and near-polar with an altitude of about 850 kilometers. The SSM/I sensor consisted of 7 separate total-power radiometers measuring the intensity of radiation coming from its Earth-viewing reflector operating at four different frequencies: 19.35, 22.235, 37, and 85.5 gigahertz.

References: RSS SSM/I Ocean Product Grids Daily from DMSP F13 NetCDF; WMO Observing System Capability Analysis and Review Tool (OSCAR) - Satellite: DMSP-F13; SSM/I and SSMIS Data in NetCDF User's Guide, Global Hydrology Research Center, The University of Alabama in Huntsville, 2012.; Wentz. F., A Well Calibrated Ocean Algorithm for SSM/I, Remote Sensing Systems.