Prospects for advanced radar-radiometer precipitation retrieval algorithms during the TRMM era

The upcoming Tropical Rainfall Measuring Mission (TRMM) to be launched in August, 1997, will offer a much improved instrumentation. In addition to a cloud-radiation budget instrument (CERES) and a lightning detection instrument (LIS) which were developed as part of the Earth Observing System (EOS), the TRMM satellite will carry a set of three new instruments principally devoted to rainfall estimation. This package includes a visible-infrared radiometer called VIRS, a multi-channel dual-polarization passive microwave radiometer called TMI (with a 10.7 GHz capability), and a 14 GHz radar which will represent the first use of a precipitation radar (PR) in space. The addition of the PR instrument creates a new space-based capability for rainfall measurement, particularly when coupled with the TMI radiometer. The two types of measuring systems are based on entirely different physical principles and thus generate markedly different signatures of the hydrometeor profile. Either type of measuring approach by itself presents certain difficulties in retrieving vertically distributed rainrate information, but combined together present various new approaches for more accurate rainfall estimation. This presentation outlines a new type of combined algorithm scheme being developed within the TRMM project called the “Tall Vector” algorithm, representing the emerging technology for the TRMM era insofar as rainfall and latent heating estimation. The basic framework of this approach, which can be considered as a type of physical inversion scheme using incongruent measurement vectors, is presented