A NOVEL SPECTRAL LINEAR TRANSFORMATION TO ESTIMATE NON-PHOTOSYNTHETIC VEGETATION COVERAGE IN NORTH ASIAN STEPPE

Nighttime light (NTL) data aids urban planning and disaster monitoring. Our study introduces HDNTL, a daily NTL dataset for 653 major cities (population >1 M by 2025) from 2012–2024, enhancing NASA's VNP46A2 accuracy by correcting spatial mismatches, angular effects, and filling small missing holes via spatiotemporal interpolation. Validated against high-resolution NTL datasets and ground-truth records, HDNTL enables precise monitoring of nighttime human activities.

The average time differences (∆T) between green-up date and snowmelt onset date from 2001–2018 on the Tibetan Plateau were 36.7 days. With the increasing spring mean temperature, spring total precipitation and daily snowmelt, ∆T became shorter. Besides, in arid and low-vegetation areas, ∆T is primarily influenced by snowmelt, whereas in humid and high-vegetation areas, temperature plays a dominant role.