Ground validation of Dual Precipitation Radar (DPR) on GPM by rapid scan Phased Array weahter Radar (PAR)

Abstract:

The core observatory satellite of the Global Precipitation Measurement (GPM) mission was launched on February 27th 2014. The Dual-frequency Precipitation Radar (DPR) on the GPM core observatory is the succession of the TRMM Precipitation Radar (PR). The DPR consists of a Ku-band precipitation radar and a Ka-band precipitation radar. The DPR is expected to be more sensitive than the PR especially in the measurement of light rainfall and snowfall in high latitude regions.

Because of the difference of spatial and temporal resolutions, Space Radar (SR) and conventional type of Ground Radar (GR) are hard to compare.The SR observes each point of earth in short time, for example one footprint is an observation in some microseconds. Rain-gauge measurements have accurate rainfall rate, but rain-gage observes small area and accumulated rainfall in some minutes. The conventional GR can cover a wide area, however, a volume scan requires several minutes.

The Phased Array weather Radar (PAR) is developed by Osaka University, Toshiba, and NICT. The PAR is a weather-radar on X-band within 100m range sampling. High spatial and temporal resolution is achieved by the PAR with pulse compression and the digital beam-forming technique. The PAR transmits a wide beam and receives narrow beams by using digital beam forming. Then, the PAR observes many elevation angles from a single pulse. The time of each volume scan is 10-30 seconds in operation, typically 30 seconds. The study shows comparisons between the DPR and the PAR by more similar spatial and temporal resolution.

The rainfall region of DPR is similar to the one of PAR. Correlation coefficient of both radar reflectivity suggests more than 0.8 in the 20km range of PAR. As a result, it is considered that DPR can observe with high accuracy. We present the case study which DPR overpassed the PAR observation region in detail.