Retrieval Of Water And Bottom Properties Of Optically Shallow Waters For VIIRS

In recent years,with the development of ocean color remote sensing satellite technology,which has a very high flexibility in marine monitoring,kinds of ocean color satellites can be used to monitor marine environment efficiently and cost-effectively combined with the advanced atmospheric correction and water depth inversion algorithms designed by many scholars,which makes remote sensing applications greatly extended to the shallow water topography and the study of the optical properties of aquatic waters.As a new water color remote sensing satellite,VIIRS ocean color satellite has a great potential in ocean monitoring.However,it's standard products(can be downloaded from NASA)does not correct the bottom effects in optical shallow water area,so for shallow water area those products(such as IOPs and Chlorophyll-a)are wrong or have large uncertainties.On the other hand,for correction,it is necessary to know the upward reflection signal from the bottom of shallow water.And active remote sensing technology,led by LiDAR technology,is developing vigorously.Lidar sensors can acquire discrete water depths all day.So how to combine this discrete water depths with ocean color satellite data,explore point-to-surface fusion remote sensing inversion model,and improve the inversion accuracy of VIIRS image in shallow water area have become a difficulty.Therefore,the purpose of this paper is to explore the possibility of improving the quality of VIIRS standard products by combining known discrete water depth points,and to obtain shallow water topography and water optical information at the same time.Many scholars have proposed kinds of models for bottom signal correction in shallow water,which are mainly divided into empirical algorithms and semi-analytical-semi-empirical algorithms.For optical shallow waters,semi-analytical inversion algorithms can be used to derive both bottom depth and water's inherent optical properties(IOPs)from sensor-derived hyperspectral remote sensing reflectance spectrum,Rrs.However,due to the limited spectral bands of VIIRS,the success of these retrievals are not uniform.Here,we show a fusion scheme to implement the semi-analytical inversion system and improve the retrieval of bottom and water properties from VIIRS Rrs.It is found that the derived bottom depth is strongly consistent(R2=0.82,RMSE= 1.49m)with that of LIDAR data.This improved bathymetry is farther used as input into the algorithm to improve the accuracy of IOPs retrieval.We present the comparisons of derived values of the absorption coefficient of phytoplankton,aph(440),the absorption coefficient of CDOM,adg(440)and,the particulate backscattering coefficient bbp(440)with the VIIRS standard products,which indicate the influence of the bottom contamination for IOPs was eliminated by the fusion scheme.In this paper,the combination of active and passive remote sensing detection technology has been applied in shallow water area of VIIRS satellite image,and the research proved that the known water depths could improve the inversion accuracy of optical parameters of VIIRS image in shallow water area,which lays a foundation for the future research of the combination of active and passive remote sensing technology.In addition,the model can be applied to mixed bottom types or single bottom dominated water body.These are of great significance for improving the quality of VIIRS products and wider application of VIIRS in marine environmental monitoring,as well as for people to accurately understand and study IOPs in shallow waters.