数据说明
GF-4 Normalized Water-Leaving Radiance at 561nm (LW2)
上传时间:2019-05-23 08:57:02 浏览次数:作者与来源:admin
LW2 is the retrieved normalized water-leaving radiance at the spectral center of the second band of the camera onboard the Chinese geostationary satellite GF-4.
Unit: mW/(cm2*µm*sr)
Resolution:  50m
Duration: 2017-2018
Source: GF-4 L1 data from the National Satellite Ocean Application Service
Version: 2018
Dataset Name: 
Processing:
The UV-AC atmospheric correction developed by He et al. (2012; 2013) was applied to the GF-4 L1 data to retrieve the normalized water-leaving radiance at different bands. Specifically, two atmospheric correction processes will be carried out. In the first atmospheric correction process, we assuming that the water-leaving radiance was zero, and the aerosol scattering radiance was estimated at 491nm. Based on the 653nm and 809nm bands, the epsilon value of the aerosol scattering was estimated by assuming that the water-leaving radiance at these two bands were zero. Then, using the estimated 491nm aerosol scattering radiance and epsilon values, the aerosol scattering radiance at all bands were calculated, and the normalized water-leaving radiance (Lw) were derived. In the second atmospheric correction process, the concentration of the total suspended matter (TSM) was estimated from the derived Lw based on the empirical TSM retrieval algorithm developed for the Changjiang River Estuary (He et al., 2013). Then, the water-leaving radiance at the 653nm and 809nm was estimated using the MUMM algorithm with the ratio of the water-leaving reflectance at these two bands as α=(2.19020+0.015*TSM)/(0.365520+0.015*TSM). Finally, the aerosol scattering radiance at 653nm and 809nm were derived by Rayleigh-correct radiance minus the water-leaving radiance, and it was extrapolated to the other shortwave bands.
Known Issues:
The UV-AC algorithm is suitable to the high turbid waters. In the clear shelf waters, it may have high uncertainty. In addition, GF-4 is not an ocean color satellite, and the signal-to-noise ratio is low, which limit the data only suitable for the turbid waters.
Reference
Xianqiang He*, Knut Stamnes, Yan Bai, Wei Li, Difeng Wang. Effects of Earth curvature on atmospheric correction for ocean color remote sensing. Remote Sensing of Environment, 2018,209:118–133. DOI:10.1016/j.rse.2018.02.042
Xianqiang He*, Yan Bai, Delu,Pan, Junwu Tang, Difeng Wang. Atmospheric correction of satellite ocean color imagery using the ultraviolet wavelength for highly turbid waters. Optics Express, 2012,20(18):20754-20770. DOI:10.1364/OE.20.020754
Acknowledgment
Please cite the above two references if this dataset is used..