Surface Water and Ocean Topography(SWOT)is a next-generation radar altimeter that offers high resolution,wide swath,imaging capabilities.It has provided free public data worldwide since December 2023.This paper aims t...Surface Water and Ocean Topography(SWOT)is a next-generation radar altimeter that offers high resolution,wide swath,imaging capabilities.It has provided free public data worldwide since December 2023.This paper aims to preliminarily analyze the detection capabilities of the Ka-band radar interferometer(KaRIn)and Nadir altimeter(NALT),which are carried out by SWOT for internal solitary waves(ISWs),and to gather other remote sensing images to validate SWOT observations.KaRIn effectively detects ISW surface features and generates surface height variation maps reflecting the modulations induced by ISWs.However,its swath width does not completely cover the entire wave packet,and the resolution of L2/L3 level products(about 2 km)cannot be used to identify ISWs with smaller wavelengths.Additionally,significant wave height(SWH)images exhibit blocky structures that are not suitable for ISW studies;sea surface height anomaly(SSHA)images display systematic leftright banding.We optimize this imbalance using detrending methods;however,more precise treatment should commence with L1-level data.Quantitative analysis based on L3-level SSHA data indicates that the average SSHA variation induced by ISWs ranges from 10 cm to 20 cm.NALTs disturbed by ISWs record unusually elevated SWH and SSHA values,rendering the data unsuitable for analysis and necessitating targeted corrections in future retracking algorithms.For the normalized radar cross section,Ku-band and four-parameter maximum likelihood estimation retracking demonstrated greater sensitivity to minor changes in the sea surface,making them more suitable for ISW detection.In conclusion,SWOT demonstrates outstanding capabilities in ISW detection,significantly advancing research on the modulation of the sea surface by ISWs and remote sensing imaging mechanisms.展开更多
The Sea Surface Height Anomaly (SSHA) from the TOPEX/Poseidon altimeter data in 1994 is assimilated into a high-resolution model of the South China Sea (SCS) with nudging method. The model results can reveal the seaso...The Sea Surface Height Anomaly (SSHA) from the TOPEX/Poseidon altimeter data in 1994 is assimilated into a high-resolution model of the South China Sea (SCS) with nudging method. The model results can reveal the seasonal variations of SSHA and its time-space migration characters,at the same time,verify the effect of assimilation.Compared with non-assimilation results,assimilation results can show the seasonal variations of SSHA better,particularly in winter.Futhermore,it can distinguish temporal-spatial migration characters of SSHA clearly,i.e. cold signal of SSHA in northern SCS propagating westward and warm signal of SSHA in central SCS propagating eastward.It shows that as an easy and effective method,data assimilation of the SSHA with nudging method could make the simulated results closer to the available observations.展开更多
基金The National Natural Science Foundation of China under contract Nos U2006207 and 42006164.
文摘Surface Water and Ocean Topography(SWOT)is a next-generation radar altimeter that offers high resolution,wide swath,imaging capabilities.It has provided free public data worldwide since December 2023.This paper aims to preliminarily analyze the detection capabilities of the Ka-band radar interferometer(KaRIn)and Nadir altimeter(NALT),which are carried out by SWOT for internal solitary waves(ISWs),and to gather other remote sensing images to validate SWOT observations.KaRIn effectively detects ISW surface features and generates surface height variation maps reflecting the modulations induced by ISWs.However,its swath width does not completely cover the entire wave packet,and the resolution of L2/L3 level products(about 2 km)cannot be used to identify ISWs with smaller wavelengths.Additionally,significant wave height(SWH)images exhibit blocky structures that are not suitable for ISW studies;sea surface height anomaly(SSHA)images display systematic leftright banding.We optimize this imbalance using detrending methods;however,more precise treatment should commence with L1-level data.Quantitative analysis based on L3-level SSHA data indicates that the average SSHA variation induced by ISWs ranges from 10 cm to 20 cm.NALTs disturbed by ISWs record unusually elevated SWH and SSHA values,rendering the data unsuitable for analysis and necessitating targeted corrections in future retracking algorithms.For the normalized radar cross section,Ku-band and four-parameter maximum likelihood estimation retracking demonstrated greater sensitivity to minor changes in the sea surface,making them more suitable for ISW detection.In conclusion,SWOT demonstrates outstanding capabilities in ISW detection,significantly advancing research on the modulation of the sea surface by ISWs and remote sensing imaging mechanisms.
基金the South China Sea Monsoon Experiment,the State Key Basic Research Program (G1999043806)the CAS Knowledge Innovation Project (KZCX2-202)the National Natural Science Foundation of China (400076007)
文摘The Sea Surface Height Anomaly (SSHA) from the TOPEX/Poseidon altimeter data in 1994 is assimilated into a high-resolution model of the South China Sea (SCS) with nudging method. The model results can reveal the seasonal variations of SSHA and its time-space migration characters,at the same time,verify the effect of assimilation.Compared with non-assimilation results,assimilation results can show the seasonal variations of SSHA better,particularly in winter.Futhermore,it can distinguish temporal-spatial migration characters of SSHA clearly,i.e. cold signal of SSHA in northern SCS propagating westward and warm signal of SSHA in central SCS propagating eastward.It shows that as an easy and effective method,data assimilation of the SSHA with nudging method could make the simulated results closer to the available observations.
