Key Method Research On Radar Precipitation Estimation Of Complex Terrain Over Thetibet Plateau

Radar precipitation estimation is a very complicated issue, and the research onit is relatively successful in the plains with better radar coverage. However,regarding to the complex terrain of the Tibet Plateau, radar precipitationestimation faces big challenges: firstly, due to its special geographicalenvironment, the ground clutter of the Tibet Plateau has some differences fromany other parts of that in the past, so the previous ground identification algorithmis not suitable for the Tibet Plateau. Secondly, the Tibet Plateau is in complexterrain, because of trees, buildings and others are not in terrain data, theconventional terrain-based hybrid scan method will result in calculation error ofthe hybrid scanning elevation. Thirdly, since the Tibet Plateau has high sea leveland low zero layer, then it has used the information for the bright band of the zerolayer and the solid-state precipitation region over it for precipitation estimation.However, as the lowest layers of radar elevation are blocked, and bright bandidentification of the revised methodology (for plains with better radar coverage)of zero layers in complex terrain is not with good correction effect, theimprovement in precipitation estimation is not obvious. The conventionalprecipitation classification of convective and stratiform clouds and theircorresponding liquid precipitation of Z-R relationship are not fit for estimation ofsolid-state precipitation or precipitation influenced by bright band over the TibetPlateau.In order to solve the difficulties and issues of precipitation estimations over theTibet Plateau, this paper uses the radar on the Tibet Plateau, and rain gauge datato improve the precipitation estimation accuracy over the Tibet Plateau throughthe study of the following four sections.1). Propose the ground clutter identification parameters fits for the Tibet Plateauaccording to the ground clutter characteristics, and uses the fuzzy logic methodsto identify ground clutter of the Tibet Plateau;2). Study the hybrid scan elevation calculation based on reflectivity climatology,so as to avoid any error produced as the terrain data does not include trees,buildings and other things;3). Regarding that the lowest layers of radar elevation are blockage, use thevertical profile of reflectivity bright band to make the identification of the revisedparameters, and correct the bright band so as to reduce the impact of the brightband on precipitation estimation;Put forward the corresponding Z-R relationshipfor different types of precipitation.This has an important significance for research on roles of clouds and precipitation over the Tibet Plateau in the aspects of energy and water cycle, andto verify various methods of satellite remote sensing of cloud and precipitationover the Tibet Plateau as well as accurate and timely forecasts of heavy localprecipitation because of debris flow and other disastrous.