Abstract: Emissivity of the surface target is an important parameter for remote sensing surface temperature retrieval, and the changes of water constituents bring about changes of water physical property and influence emissivity. However, studies on influences of water body constituent on emissivity are rare at the present. In this study, we determined the influences of blue-green algae and suspended sediments on water body emissivity using the Nicolet iS50 FT-IR spectrometer of Thermos Scientific Co. Ltd with an integrating sphere of the PIKE technologies, and proposed a method to obtain case II water emissivity. Based on the classic split window method and the MODIS datasets, we compared the water surface temperature retrieved using the proposed emissivity with the temperature retrieved using the widely-used water emissivity. Analysis indicates that blue-green algae and suspend solid do have influences on water body emissivity, and suspend solid has greater influence. The maximum influence on surface temperature retrieval is 1.21℃ when we take blue-green algae and suspend solid into a comprehensive consideration. The maximum influence of blue-green algae is 0.86℃ when suspend solid concentration is low. The maximum influence of suspend solid is 0.98℃ when blue-green algae concentration is low. In the actual retrieval and authenticity test, the concentrations of blue-green algae and suspended solid are low, the overall maximum influence on surface temperature retrieval is 0.78℃, and the impacts at most of the validation samples are between 0.53℃ and 0.78℃. Experiment shows that the introduction of emissivity correction function based on the chlorophyll-a concentrations of the blue-green algae and suspended sediments considerably reduces errors in water surface temperature retrieval.

Key words: concentration of the chlorophyll a, concentration of suspended sediments, emissivity, surface temperature retrieval