Researchers evaluate performance of MODIS land reflectance products in water monitoring

Satellite tv for pc ocean shade devices are used to characterize bodily, chemical, and organic variabilities in oceanic, coastal, and inland waters. Nonetheless, the large loss and huge uncertainty of distant sensing reflectance knowledge end in issue in monitoring nearshore coastal and inland waters.

A lot of the coastal and inland waters are typically turbid; in these areas, the contribution of water to alerts of prime environment is raised, suggesting the potential of utilizing land reflectance merchandise for water monitoring. The Average Decision Imaging Spectroradiometer (MODIS) floor reflectance product (R_land) has been used to watch water readability and suspended solids in waters.

Just lately, a analysis group led by Profs. Duan Hongtao and Ma Ronghua from the Nanjing Institute of Geography and Limnology of the Chinese language Academy of Sciences has offered a complete analysis of the efficiency of MODIS R_land merchandise towards a subject optical dataset. The dataset accommodates 4,143 reflectance spectra, 2,320 chlorophyll-a samples, and 1,467 suspended particulate matter samples throughout international nearshore coastal and inland waters.

This work was revealed in Earth-Science Opinions.

“Regardless of the benefit of utilizing this product and its larger spatial decision than the MODIS ocean bands, in line with our evaluation, R_land may not be an optimum knowledge supply for monitoring inland and coastal waters,” mentioned Prof. Duan.

The outcomes confirmed that R_land overestimated remote sensing reflectance, notably in 469 nm and 859 nm bands. As well as, land reflectance confirmed evident overestimations in contrast with the ocean shade merchandise derived utilizing SeaDAS software program within the East China Sea.

The researchers additionally reported noticeable unfavourable values and patchiness within the R_land imagery. R_land was continuously unfavourable within the pixels lined by cyanobacterial scums. “The negatives and patchiness in R_land probably resulted from [an] unsuitable mechanism to take away aerosols in producing R_land over waters,” mentioned Prof. MA.

Current algorithms didn’t estimate passable chlorophyll-a and suspended solids from R_land throughout the worldwide inland and coastal waters. Machine studying fashions outperformed the state-of-the-art algorithms for suspended particulate matter retrievals in international turbid waters from R_land.

Nonetheless, not all fashions, together with machine studying fashions, can retrieve dependable chlorophyll-a from R_land, because of the restricted spectral info and uncertainty of R_land merchandise. This means that R_land would possibly be capable to quantify the parameters intently associated to suspended solids (e.g., water readability and extinction coefficients) in most waters; nevertheless, it’s difficult to quantify pigments like chlorophyll-a.

“MODIS R_land doesn’t comprise enough info that makes these present algorithms usable. Consequently, numerous water shade parameters from R_land are troublesome to retrieve apart from a number of parameters, comparable to suspended particulate matter, turbidity, and water clarity,” mentioned Prof. Duan.