Impacts of land use and land cover changes on regional climate in the Lhasa River basin, Tibetan Plateau

Abstract

Land use and land cover change (LUCC) can alter land surface-atmosphere interactions in the exchange of energy fluxes, with additional consequences on temperature. Understanding the impacts of LUCC on the regional climate contributes to providing fundamental information for future land use planning and regional policy orientation, especially in extremely vulnerable and sensitive plateau regions. This study was designed to explore the regional climate effects associated with LUCC in the Lhasa River basin of Tibetan Plateau using the Weather Research and Forecasting (WRF) model, with a particular focus on near-surface air temperature (Ta) and surface energy fluxes. Two numerical experiments (Case 1980 and Case 2015) were simulated, spanning from November 2014 to November 2015 with the first month as spin-up. The results indicated that the conversion from croplands or grasslands to urban and built-up land led to a noticeable increase in Ta (0.23 °C) during summer. In areas converted from grasslands to waters, Ta decreased by 0.40 °C during spring and approximately 0.50 °C during winter. The afforestation activities at this scale had an obvious impact on the Ta in spring and winter, increasing by 0.20 °C and 0.10 °C, respectively. Generally, the latent heat flux (LE) and sensible heat flux (H) were more sensitive to land conversions, while changes in other fluxes seemed to be weaker. Due to the small change in net radiation (Rn) and ground heat flux (G), the H generally showed an opposite trend with that of LE. Urbanization and reservoir construction resulted in a decrease in the LE, while afforestation construction contributed to an increase in the LE. Our study highlights the impacts of current regional development in the plateau areas on the climate, especially in spring and winter. Urbanization led to a slight warming effect; the cooling effect was more significant in spring and winter than in summer after reservoir construction, and the current afforestation project contributed to a warming effect in winter. This study contributes to the future development of environmentally compatible and sustainable land strategies.