A preliminary study of Aqua/MODIS snow coverage continuity with simulated band 6

Abstract

Snow cover is one of the sensitive indicators of global climate change. Numerous studies have shown the importance of accurate measurements of snow cover. The Moderate Resolution Imaging Spectroradiometer (MODIS) is well suited to the measurement of snow cover because snow characteristically has high reflectance in the MODIS Visible (VIS) and low reflectance in the MODIS Shortwave Infrared (SWIR) wavelengths, a characteristic that allows for snow detection by a normalized ratio of VIS and SWIR bands. The automated MODIS snow-mapping algorithm uses at-satellite reflectance in MODIS VIS band 4 (0.545-0.565 μm) and SWIR band 6 (1.628-1.652 μm) to calculate the Normalized Difference Snow Index (NDSI). Aqua MODIS band 7 (2.105-2.155 μm) instead of band 6 has been used to calculate NDSI, in response to band 6 striping problem caused by non-functional or noisy detectors. In our early study, a feasible algorithm to map Aqua MODIS band 6 based on the relationship between Terra MODIS bands 6 and 7 has been developed and validated. This algorithm has been used to retrieve Aqua MODIS band 6. Aqua MODIS NDSI values computed from Aqua MODIS observed band 6, simulated band 6, and observed band 7 are used to map snow based on current MODIS snow algorithm, respectively. Snow coverage mapped using NDSI computed from observed band 6 is regarded as a standard snow product, comparison and analysis are performed between snow mapping using NDSI computed from simulated band 6 and observed band 7. This paper will investigate the measurement continuity between Terra and Aqua MODIS snow coverage products, and propose another alternative for Aqua MODIS NDSI retrieval. Our approach for monitoring snow coverage is valuable to keep the continuity and consistency for MODIS snow products.