Typhoon Waves Remote Sensing And Impact Of Infragravity Waves On Sea Surface Elevation Measurement

Satellite remote sensing can obtain ocean gravity waves in a wide range,quickly and accurately.Synthetic aperture radar(SAR)has a variety of sampling modes,which can achieve all-time,all-weather observations of the sea surface and play an important role in the detection of typhoon waves.This study presents a new approach for a variety of SAR modes to calculate typhoon wave parameters(significant wave height Hs,dominant wave period Tp)only from SAR-retrieved wind speed utilizing fetch-or duration-limited parameterized models(H-model).In addition,with the development of satellite remote sensing technology,ocean gravity waves are also likely to affect observations of sea surface elevation by satellite.The sea surface elevation caused by Infragrivity Waves(IGW)can be captured by the future wide-swath altimeter SWOT(Surface Water and Ocean Topography),effecting on inversion accuracy of meso-scale or submeso-scale ocean circulation.Therefore,based on the global IGW numerical model,this paper quantitatively estimates the interference of IGW when using SWOT satellites to observe the sea surface elevation.Based on the wind data of Radarsat-2 ScanSAR model and Sentinel-1 SAR wave model,this paper simulates the typhoon wave parameters using the H-model models.Comparing the results of H-model with the data of wave numerical model Wavewatch III(WW3)and ESA Sentinel-1 Level-2 production respectively,we find that computed wind-sea Hs and Tp using H-models for ScanS AR mode is in good agreement with the simulation of WW3.The H-models do better for calculating Hs than Tp,with coefficient correlation more than 0.7 and 14%NRMSD.For SAR wave mode,the computed wind-sea Hs using H-models is in good agreement with the Level-2 product and the best one of models has a 0.88 RMSE and 0.86 coefficient correlationBased on the global IGW numerical model,taking the Northeastern Pacific and the North-west Europe Shelf where IGW is strong as the research area,the sea surface elevation caused by IGWs are estimated.Comparing these results with the orbit noise simulated by SWOT Simulator(± 5cm),the IGW 'noise' is quantitatively analyzed for the first time.We found that the sea surface elevation of the order of 1 cm contributed by IGWs is an important source of error that cannot be ignored in surface elevation measurements of SWOT.On the North-west Europe continental shelf,contribution of the winter IGWs to sea surface elevation has reached 25%of the initial requirement for noise level for the SWOT.While,for the U.S West coast with the narrow continental shelf,IGWs are generated along shorelines and quickly spread into the Deep Ocean,causing significant noise effect in a broader area,about 15%of the initial error level of SWOT.