Research on Data Simulation Method of Geostationary Doppler Weather Radar

The observation of global precipitation is important to climate change and environmental research. Thus, the acquisition of the global rainfall data is essential, especially the tropical rainfall data that account for two thirds of global rainfall totals. However, the detection capability of ground-based and air-borne weather radar are limited by the maximum detection range, the working time, the earth's surface and the complicated electromagnetic jamming condition in the lower atmosphere, space-borne weather radar is the only three-dimension remote sensing instrument that can directly obtain global precipitation observation all weather and round the clock effectively (Kozu T, 2001).

Geostationary Doppler weather radar (GDWR), which is a novel and challenging instrument concept for monitoring hurricane over a circular disk coverage of approximately 5300km in diameter, was first put forward by NASA’s Earth Science Technology Program (E. Im, 2003). Compared with the LEO space-borne weather radar, GDWR has many advantages, such as high frequency and wide area coverage. It can provide global rainfall observations every half hour or even short time which is very helpful in strengthening the monitoring of disastrous weather, such as strong storm and typhoon. Besides, the observation of GDWR can provide environmental field information with much high time resolution which can help develop more accurate weather forecasts. However, conclusion at present, GDWR is still at research phase without actual observation. Thus, the research on the simulation method of GDWR observation is beneficial to revise the technical parameters and evaluate detection capability in early design stages.

Since airborne weather radar (the second airborne precipitation radar, APR-2) and GDWR have the same downward-looking scanning mode, the rainfall events data which was detected by airborne weather radar can be used to simulate the observation data of GDWR with a spiral scan up to 4°. Certainly many factors need to be considered during the simulation, such as the effect of surface clutter at large scan angle, the different parameters tween airborne weather and GDWR, geometrical relationship of satellite-ground and so on.

The contents of this article are mainly consisted of the following parts:

(1) The back scattering properties of different surface should be studied firstly because surface clutter will affect rainfall data quality at large scan angle. Thus, the normalized radar cross-section (NRCS) and statistical property of sea surface and land surface were be researched. After analyzing the NRCS of land and sea surface base on TRMM measurement, the mathematical mode of surface clutter at 8 millimeter wave was established.

(2) Taking into consideration the relationship of satellite and ground, antenna’s performance parameters, the antenna direction deviation due to attitude deviation of satellite, different sample volume and other factors, the paper summery current method and design a set of simulation method of GDWR primary data. Fig.1 is a flowchart for a simulation method of GDWR primary data with APR-2 data.