Evaluation of SAR-based Sea State Parameters and Roughness Length Derivation over the Coastal Seas of the United States
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing（2024）
摘要
This paper presents comprehensive validation of specific sea state parameters (SSPs) and SAR-derived wind speeds (
u
SAR
). The paper introduces a novel approach to retrieving roughness length (z
0
) based on wave steepness, following the retrieval of the short wavelengths necessary to estimate z
0
. The Synthetic aperture radar (SAR) onboard the Sentinel-1 (S1) satellite was used specifically the Interferometric Wide Swath Mode (IW) data. The data was processed using the CWAVE_EX algorithm for SSPs and CMOD-5 for
u
SAR
CWAVE_EX was developed especially for coastal waters; the processing chain includes steps for SAR image denoising and eliminating image artifacts. SAR S-1 data inherently exhibits a substantial azimuthal cutoff length due to the data's high satellite altitude and SAR IW resolution. That complicates the retrieving of short wavelengths prevalent in coastal zones and needed to retrieve z
0
The research focuses on the coastal seas of the United States, benefiting from the presence of an extensive network of ocean buoys for validation purposes. The complete SAR S1 A/B archive from 2014 to 2022 was first processed to retrieve SSPs and
u
SAR
The validation for significant wave height (
Zs
), second moment wave period(
T
m2
) and
u
SAR
was performed using in-situ measurements with about 6,000 collocations.
Hs
and
T
m2
were compared against the corresponding parameters from hindcast spectral numerical model data with about 380,000 collocations. The comparisons between the retrieved
H
s
and
T
m2
against the in-situ observations and hindcast wave model data yielded a root mean square error (RMSE) of 0.46-0.50 m and 0.9-1.1 sec. The RMSE of
u
SAR
against in-situ observation was about 2 m/s with a bias of 0.78 m/s. The estimated z
0
values from satellite-driven wave parameters were highly correlated with the z
0
estimated from the in-situ observations, with a RMSE of 0.04×10-3 m and a bias of -0.01×10-3 m. The study highlights the possibility of using SAR remote sensing data for global mapping of z
0
, including coastal effects of local variability in sea state and wind field gustiness.
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关键词
SAR,integrated sea state parameter,air-sea interaction,roughness length,CWAVE_EX,JONSWAP,neutral stratified wind,geophysical model function
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