5/20/2023 0 Comments Pixel cloud after effects![]() ![]() ![]() However, such noises did not appear in the other indices. These residual clouds significantly decreased NDVI values during the leaf growing season. Our results revealed that residual sub-pixel clouds potentially contaminated about 40% of the MODIS data after cloud screening by the state flag of MOD09 product. We conducted in situ continuous observation at a Japanese deciduous forest for over a year and compared the MODIS spectral indices with the cloud-free in situ spectral indices. This study investigated the noises caused by residual sub-pixel clouds on several frequently-used spectral indices (NDVI, EVI, EVI2, NDWI, and NDII) by using in situ spectral data and sky photographs at the satellite overpass time. It is important for accuracy improvement in various terrestrial remote sensing applications to clarify the influence of these residual clouds on spectral vegetation indices. Sub-pixel clouds are especially difficult to identify and remove. Cloud contamination is one of the severest problems for the time-series analysis of optical remote sensing data such as vegetation phenology detection.
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