Use of the sea surface as reference for GPM dual-frequency radar algorithms

In airborne and spaceborne radar remote sensing of clouds and precipitation, measurements of the sea surface normalized radar cross section σ are widely used to constrain and condition algorithms for the retrieval of atmospheric parameters. In the Tropical Rainfall Measuring Mission, the Path Integrated Attenuation (PIA) of the Ku-band Preciptitation Radar (PR) are estimated by comparing the surface radar backscatter measured across a distribution of hydrometeors against the surface backscatter cross section σ clear measured in the nearby rain-free areas. The PIA is then used as a constraint in the Surface Reference Techniques (SRT) to deduce the vertical rainrate profiles and surface rain rates. A dual-frequency version of the SRT is expected to be used by the planned Global Precipitation Measurement (GPM) mission since the Dual frequency Precipitation Radar (DPR) on board the GPM core satellite will provide co-located and simultaneous measurements of σ at Kuand Kaband.