Water Optical Property of High-Altitude Lakes in the Tibetan Plateau

Measurements from the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi National Polar-orbiting Partnership (SNPP) from 2012 to 2019 are used to derive the normalized water-leaving radiance spectra $nL_{w}(\lambda)$ in high-altitude lakes over the Tibetan Plateau (TP) (elevation of x007E;4 km). $nL_{w}(\lambda)$ spectra in various lakes in the TP show a significant water optical property diversity in terms of $nL_{w}(\lambda)$ spectral shapes, their magnitudes, and their spatial and temporal variations. In the TP major lakes, $nL_{w}(\lambda)$ spectra in Lake Namtso and Siling Lake show enhancements at the blue wavelengths of 410 and 443 nm [$nL_{w}$ (410) and $nL_{w}$ (443)], and peak at the wavelength of 486 nm [$nL_{w}$ (486)]. In Lake Ngangze, the $nL_{w}(\lambda)$ spectrum shows the optical feature of typical eutrophic waters. Its $nL_{w}(\lambda)$ peaks at the green wavelength of 551 nm [$nL_{w}$ (551)] with its value x007E;2.5 mW cm$<^>{-2}_{\mathrm {}}\,\,\mu \text{m}<^>{-1}$ sr$<^>{-1}$ . In Dogai Coring Lake, the typical $nL_{w}(\lambda)$ spectrum is similar to those of many smaller and medium size lakes in the TP, and $nL_{w}(\lambda)$ spectra are featured with the peak at the green band $nL_{w}$ (551) with another notable red band $nL_{w}$ (671) over x007E;1.0 mW cm$<^>{-2} \mu \text{m}<^>{-1}$ sr$<^>{-1}$ , as well as a nonnegligible contribution at the near-infrared (NIR) band $nL_{w}$ (745). This implies that the suspended particle matter (SPM) in the lake plays a significant role in water $nL_{w}(\lambda)$ spectra in Dogai Coring Lake and other similar lakes in the TP. The diversity of water optical property in the TP lakes reflects the fact of the regional diversification of processes in various TP lakes and poses potential challenges to the development of remote sensing algorithms for water biological and biogeochemical products in the TP lakes.