Modeling the effects of vegetation greening on frozen ground over the Qinghai-Tibet Plateau

Vegetation greening on the Qinghai-Tibet Plateau (QTP) plays a crucial role in altering the energy balance and frozen ground conditions. As vegetation cover increases, albedo decreases, leading to surface warming. This study used high-resolution land-use datasets from different time periods to parameterize plant functional types (PFTs) on the QTP and conducted sensitivity simulations with the RegCM5.0-CLM4.5 model. By comparing land cover changes (LCC) across different years, the study evaluated the effects of vegetation greening on energy balance and frozen ground dynamics. The results show that LCC caused significant warming, with land surface temperature (LST) increasing by 0.10°C in 2000 and 0.36°C in 2020.  Soil temperature (ST) changes were observed as deep as 280 cm, with the largest variations between 2 cm and 100 cm depths, leading to increases of 0.07°C (in 2000) and 0.31°C (in 2020).  This warming intensified frozen ground thawing, expanding thawing regions and shrinking freezing areas.  Variations in LST and energy flux components were regionally dependent, influenced by meteorological factors and circulation patterns.  The findings underscore that vegetation greening, by reducing albedo, reshapes energy fluxes, increasing air temperature, LST, and ST, while accelerating thawing and reducing freezing in frozen ground regions.