[S-TT39] Synthetic Aperture Radar and its application

[STT39-04] High-resolution imaging of oceanic heavy rain signals by ALOS-2 full-polarimetry

*Masato Furuya¹, Ito Ide² (1.Department of Earth and Planetary Sciences Hokkaido University, 2.Earth and Planetary Sciences, Faculty of Science, Hokkaido University)

Keywords:ALOS-2, SAR, heavy rain, oceanic area, full polarimetry

Advanced Land Observing Satellite-2 (ALOS-2), launched by JAXA in 2014, carries Phased-Array type L-band Synthetic Aperture Radar-2 (PALSAR-2) that delivers high-spatial-resolution radar images to monitor natural disasters such as earthquakes, volcanic eruptions, floods, and so forth. Besides land areas, PALSAR-2 imageries over oceanic regions have been used to estimate surface winds and sea-ice distributions. However, there are few observation reports of heavy rain episodes over oceanic areas by PALSAR-2, while rain signals would become noise for wind velocity retrieval. Alpers et al (2016) reviewed radar imaging of rain footprints over the ocean but focused mostly on C-band radar images. Here we report two heavy rain episodes over the ocean off south Kyushu imaged by ALOS-2/PALSAR-2 full-polarimetric mode, whose maximum spatial resolution is ~6m.
Figure 1 indicates the amplitude image of the HH-channel acquired on August 11, 2021 with a darker (brighter) area indicating weaker (stronger) scattering amplitude. Comparing Figure 1 with the JMA's rain radar map at the epoch, we confirm that the darker (brighter) area corresponds to higher (lower) rain-rate area. By analyzing other channels, HV, VH, and VV, we aim to map the rain intensity distribution with high-spatial-resolution.