Dual-Frequency Radar (DPR) and the Global Precipitation Measurement (GPM) in Japan

摘要

The Global Precipitation Measurement (GPM) is a successor of the Tropical Rainfall Measuring Mission (TRMM) which has opened a new era for precipitation system measurement from space including much better global rain maps. The scope of GPM is much wider than that of TRMM. GPM will provide three hourly precipitation measurement over the globe, that is, much higher temporal resolution with wider coverage than TRMM. Current precipitation measurement is far from enough for the water resources management which requires very high spatial and temporal resolution. The three hourly global precipitation measurement with GPM will greatly contribute not only to the precipitation sciences but to real-world applications. The GPM core satellite will be equipped with a dual-wavelength radar (DPR) and a microwave radiometer, and will work as a reference standard for the GPM constellation radiometers. The development of the space segment is going well, and the core satellite launch is scheduled in the middle of 2013. DPR is a 14/35 GHz radar system. The 14 GHz radar is similar to the TRMM precipitation radar but the 35 GHz radar is a new one with scanning ability. The rain retrieval algorithms using DPR is underway. The basic idea is to use the difference of rain attenuation at two frequencies in the liquid layer, and the deviation from the Rayleigh scattering in the solid precipitation layer. Field experiments for the DPR algorithm development are also designed. A dual Ka-band radar system which is now being developed will be a powerful tool for the field experiments. The dual Ka-radar system can measure both the specific attenuation and the equivalent radar reflectivity at Ka-band.