Masanori Nishikawa
(Nagoya University, Japan)

A dual Ka-band radar system is developed by the Japan Aerospace Exploration Agency (JAXA) for the Global Precipitation Measurement (GPM) dual-wavelength radar (DPR) algorithm development. The usage of the system is two-fold: one is to measure backscattering cross section and extinction cross section by precipitation separately, and the other is to provide testbed data for the DPR algorithm. The parameters required in the DPR algorithm are raindrop size distribution for the liquid precipitation, and particle density, shape, and melting ratio for the solid precipitation. DPR will provide two precipitation profiles at Ka and Ku-bands. The two profiles will be interpreted in terms of the backscattering and extinction cross sections, and water-equivalent precipitation rate could be estimated using the relationships between the cross sections and the parameters of precipitation particles. When the two Ka-radar systems separated by 10-20 km observe precipitation in between two radars, the specific attenuation can be measured. Along with other radar, such as a C-band radar, so-called Mie scattering effect which is deviation from Rayleigh scattering could be estimated. A field experiment using the dual Ka-radar system is conducted in Okinawa Island. A C-band polarization Doppler radar is also operated, and preliminary result is presented.

Katsuhiro Nakagawa
(NICT, Japan)

A dual Ka-band radar system is developed by the Japan Aerospace Exploration Agency (JAXA) for the Global Precipitation Measurement (GPM) dual-wavelength radar (DPR) algorithm development. The usage of the system is two-fold: one is to measure backscattering cross section and extinction cross section by precipitation separately, and the other is to provide testbed data for the DPR algorithm. The parameters required in the DPR algorithm are raindrop size distribution for the liquid precipitation, and particle density, shape, and melting ratio for the solid precipitation. DPR will provide two precipitation profiles at Ka and Ku-bands. The two profiles will be interpreted in terms of the backscattering and extinction cross sections, and water-equivalent precipitation rate could be estimated using the relationships between the cross sections and the parameters of precipitation particles. When the two Ka-radar systems separated by 10-20 km observe precipitation in between two radars, the specific attenuation can be measured. Along with other radar, such as a C-band radar, so-called Mie scattering effect which is deviation from Rayleigh scattering could be estimated. A field experiment using the dual Ka-radar system is conducted in Okinawa Island. A C-band polarization Doppler radar is also operated, and preliminary result is presented.

Seiji Kawamura
(NICT, Japan)

Ground validation (GV) of satellite data and retrieval algorithms is essential for GPM/DPR to secure the quality of precipitation estimates. Okinawa Sub-tropical Environment Remote Sensing Center of NICT (National Institute of Information and Communications Technology) has various instruments to observe the precipitation in Okinawa Island, COBRA (C-band polarimetric weather radar), 400-MHz wind profiler radar (400-MHz WPR, which can derive raindrop size distributions), 2D-Video distrometers (2DVD), Joss-type disdrometers, Parsivel (Laser Optical) disdrometers, Micro-rain radars (MRR), and so on. The intensive field observations for subtropical precipitation were conducted with these instruments in these years. We have started observations to estimate the error of various physical parameters in the precipitation retrieval algorithms (e.g. attenuation factor, drop size distribution, terminal velocity, density of the snow particles, etc.) for GPM/DPR algorithm validations. After the launch, we have a plan to perform end-to-end comparisons between instantaneous precipitation data observed by satellite and ground-based instruments in Okinawa. Our super site in Okinawa and GV plan for GPM/DPR are introduced.

Shigeo Sugitani
(NICT, Japan)

The Global Precipitation Measurement (GPM) mission is a comprehensive program to measure precipitation from space, similar to but much expanded beyond the Tropical Rainfall Measuring Mission (TRMM). Its scope is not limited to scientific research, but includes practical and operational applications such as weather forecasting and water resource management. To meet the requirements of operational use, the GPM uses multiple low-orbiting satellites to increase the sampling frequency and to create three-hourly global rain maps that will be delivered to the world in quasi-real time. A Dual-frequency Precipitation Radar (DPR) will be installed on the primary satellite that plays an important role in the whole mission. The DPR will realize measurement of precipitation with high sensitivity, high precision and high resolutions. This paper describes an outline of the GPM/DPR onboard calibration method, and development of Radar Calibrators (RC).

Shuji Shimizu
(JAXA, Japan)

Comparisons of the precipitation products of the Precipitation Radar (PR) of Tropical Precipitation Measuring Mission (TRMM) satellite and several rain map products (TRMM 3B42, GSMaP, etc.) using TRMM satellite and some microwave imagers with ground-based observation networks (radars, raingauges, etc.) in the Asian countries indicated that underestimation of PR version 6 rain products and local discrepancies between satellite data and ground-based data, especially orographic rainfall and coastal rainfall data. In order to improve the precipitation retrieval algorithms and tune the precipitation map products, the accumulation of the results of comparisons between satellite data and accurate and high-resolution (spatial and temporal) ground-based data in several areas and precipitation regimes are essential. Dual-frequency Precipitation Radar (DPR) on the core satellite of Global Precipitation Measurement (GPM), which is being developed by Japan Aerospace Exploration Agency (JAXA) and National Institute of Information and Communications Technology (NICT) and will be launched in 2013, and the synergy with microwave imagers on the constellation satellites will provide more high-accurate and high-frequency precipitation products. In the GPM era, we expect that the precipitation products will be used to several applications; flood warning, weather prediction, etc.

Nozomi Kawamoto
(Remote Sensing Technology Center of Japan, Japan)

We have analyzed rainfall data observed by Precipitation Radar (PR) on board Tropical Precipitation Measuring Mission (TRMM) to compare with AMeDAS ground rain gauge network in Japan. PR has observed latitudes of 35 degrees north-south and visited Japan a few times a day. Annual rainfall of 1998-2008 excluding 2001, are calculated in boxes of area size of 0.5x0.5 - 5x5 degrees. It is found that PR rainfall is smaller that AMeDAS rainfall over Japan (more than ~-20% in large areas). We estimated sampling errors and retrieval errors are respectively and found that sampling errors are sufficiently small in this calculation, and retrieval errors are large and account for most of all errors. In addition, retrieval errors are small in the Seto inland sea area with light rainfall, and large in the Pacific Ocean side with heavy rainfall and the mountain district with heavy snowfall. Retrieval errors seem to depend on the rain system and geographical features. In order to investigate factors caused large errors, PR and AMeDAS rainfalls observed in same times are compared. It shows that PR has a tendency to underestimate of rain when AMeDAS observes heavy rain of over 10mm/h.