A Feasibility Study on Wide Swath Observation by Spaceborne Precipitation Radar

A feasibility study on wide swath observation assuming future spaceborne precipitation radar was demonstrated using data obtained from a wide swath observation experiment conducted in September 2017 by using the dual-frequency precipitation radar onboard the global precipitation measurement core observatory. In this experiment, scan angles of the Ku-band precipitation radar (KuPR) and Ka-band precipitation radar (KaPR) were experimentally changed to observe from nadir to about +34°. While the result showed that the precipitation echo could be obtained at wider scan angles, the occurrence of sidelobe and grating lobe clutters not seen in a normal scan were simultaneously observed. The mainlobe clutter height of KuPR increased linearly along the incident angle, and 0.5 mm/h precipitation may be masked up to 4 km over land at the angle of +34°. Besides, the grating lobe clutter clearly occurred in KuPR when the ground surface of the grating lobe direction was land or sea ice. The maximum scan angle without the grating lobe contamination was +23.43°, approximately corresponding to 355 km swath width with the orbit altitude of 407 km. For KaPR, the grating lobe contamination was not significant and the mainlobe clutter height peaked at the scan angle of around 26°, and then tended to decrease at larger scan angles. Therefore, precipitation at the lower altitude may have a chance to be detected even at larger scan angles, while weaker surface echoes at larger scan angles may need new techniques to estimate precipitation for the KaPR.