Analysis of the GPM/DPR wide swath experiment assuming future spaceborne precipitation radar

Abstract

The observation from spaceborne precipitation radar has been contributed to better understanding of earth climate system. Global Precipitation Measurement (GPM) core satellite Dual-frequency Precipitation Radar (DPR) provides us 3- dimentional information of precipitation by the scan width of about 250 km, but there has been an argument that to bring systematic impact on the weather forecasting and monitoring, wider swath observation is necessary. Based on those discussions, the scan pattern of GPM/DPR was experimentally changed for 1 day from 13UTC on September 26th. In this experiment, the scan angle was changed to observe from nadir to about +34° assuming future spaceborne precipitation radar with wider swath width, while in the normal observation DPR scans ±17°. The height and strength of the surface echo clutter with larger incident angle were assessed statistically to examine the possibility of the rainfall retrieval with wide swath observation by DPR. For the observation with the Ku band, the result shows that the clutter top height at the larger incident angle over ocean is somehow suppressed at around 4 km while over land it increases almost linearly up to around 5 km. The same tendency is found on the Ka band observation, but it has lower clutter top height of around 2.5 km and 3.5 km, over ocean and land respectively. The results also indicate that relatively intense rainfall can be retrieved while shallow rainfall with weak echo power may not be acceptable for retrieval because it should be masked by the surface clutter.