Analysis of Wind and Waves from SWIM on-board CFOSAT: A gen-next altimeter

Suchandra Bhowmick (Space Applications Centre, India)


Seemanth M (Space Applications Centre, India)

Event: 2020 Ocean Surface Topography Science Team Meeting (virtual)

Session: CFOSAT

Presentation type: Type Forum

Ocean surface wind, waves and currents interact at various scales resulting in crucial processes that greatly affect the weather phenomenon. These processes are less understood and hence are unaccounted for in various numerical models that are used to predict weather and ocean state. Understanding of these ocean processes need synergistic measurements of various physical paramaters at high spatial resolution. This still remains a challenge for earth observing satellites. Surface Waves Investigation and Monitoring instrument (SWIM) on-board CFOSAT is a technological innovation paving path for wide swath altimeters. It is dedicated for synergistic measurements of wind and waves parameters. Unlike traditional altimeters whose measurements are based on specular reflection, SWIM have rotating antenna that can operate in 6 incidence angles ranging from 0 through 10°. SWIM operates at frequency of 13.5 Ghz (Ku band) in the VV polarization. It provides wind and the essential wave spectra information from which wave parameters can be extracted. In this study CFOSAT wind/wave from nadir and off-nadir measurements are validated using reference mission of Jason-3 along with observations from buoys deployed by NDBC and INCOIS for a brief period of March-May 2020. The validation indicated the nadir measurements of SWIM are of extremely high quality and is at par with the traditional altimeters. At nadir, RMSE of SWH is 0.39 m and 0.31m with respect to Jason-3 and global buoys. The wind accuracy is 0.67 m/s and 1.55m/s corresponding to Jason-3 and Buoys. Off nadir measurements are fair in terms of accuracy. Far range is found to be more accurate as compared to the near range. After this brief phase of validation, SWIM SWH is assimilated into the numerical wave model WAVEWATCH-III (WWIII). The results are validated using the buoy observation and are found to be encouraging.
Suchandra Bhowmick
Space Applications Centre