Abstract
This review paper serves for two purposes : describing the algorithm currently used by JAXA to produce precipitation product from AMSR/AMSR-E data and discussing two most important challenges facing passive microwave precipitation algorithm development. The precipitation algorithm used in JAXA today combines emission and scattering signatures, includes a correction for beam-filling problem, and has been validated by surface radar-gauge network data and other satellite retrievals. Because we pieced together all the modifications to the original version of the algorithm in this paper, this article gives the most complete description to the current version of the algorithm, and therefore, can serve as a reference for the precipitation product users to cite. The discussion on the challenges, beam-filling and ice scattering, in passive microwave precipitation retrievals is aimed to more general audiences. While the footprint size of the recent satellite microwave sensors is finer than earlier ones, the beam-filling problem seems still to be one of the most important error sources in current retrieval algorithms. The ice scattering problem is important for retrieving snowfall and precipitation over land since the primary signature for these applications is scattering signal.
