Observation-Based Evaluation of Local Climate Effect of Terrestrial Vegetation in Temperate Zones

Terrestrial vegetation modulates the land-atmosphere dynamics and is one of the fundamental forces for climatic variability. The vegetation feedback may enhance or offset a portion of ongoing global warming. However, it is challenging to disentangle the role of vegetation from the effect of other drivers, primarily due to lacking suitable reference without vegetation. Fortunately, China has recorded the land surface temperature (LST) on bare land in 2400s weather stations, providing a deal bare-land reference. Here, we used satellite measurements of the vegetation's canopy temperature, contrasted with the surface temperature of bare land, to quantify the vegetation's effect on LST. Results show that vegetation has a cooling effect during daytime and a warming effect at night, and the magnitude of the former is significantly higher than that of the latter. Consequently, vegetation has a net cooling effect and reduces LST up to 2.18 degrees C in China. Spatially, the cooling effect of vegetation decreases by 0.25 degrees C for a unit increase of latitude. Based on land surface energy balance, the spatial pattern of vegetation's net effect is mainly driven by vegetation-induced evapotranspiration and albedo. As latitude increases, the decrease of vegetation density significantly reduces the evapotranspiration-induced cooling effect while having no distinct impact on the albedo-induced warming effect. As a result, the net cooling effect of vegetation has an evident latitudinal gradient and a clear seasonal contrast. Additionally, the vegetation's effect on LST is sensitive to solar radiation and snow cover changes.