The biophysical effects of the vegetation restoration program on regional climate metrics in the Loess Plateau, China

The Grain to Green (GTG) program launched in 1999 by the Chinese government is one of the largest ecological restoration programs ever implemented in the world. Although the GTG program has been demonstrated to affect ecosystem services in the revegetated areas, its impacts on regional climate are seldom reported and poorly understood. Therefore, our study examined the impacts of revegetation owing to the GTG program on summer climate in the Loess Plateau, by incorporating near real-time remotely sensed land use/land cover data and vegetation characteristics of 2001 and 2010 into a coupled land-atmosphere model. From 2001 to 2010, a considerable portion of croplands was converted to forests and grasslands, with vegetation fraction and LAI increasing while surface albedo decreasing throughout the Loess Plateau. Compared with those from 2001, simulation results from 2010 indicated lowered 2-m air temperature in summer, with the magnitude of reduction in nighttime minimum (as high as 0.8-1.0 degrees C) greater than that in daytime maximum (generally restricted to 0.4 degrees C). The concurrent decrease in summertime 2-m specific humidity further led to widespread reduction of near-surface heat content (i.e., moist enthalpy). Summer precipitation decreased in northern Shanxi province and western Loess Plateau (up to 1.0-1.4 mm/day) while increasing in southeastern Loess Plateau (between 1.0-2.0 mm/day). Our findings underscore that vegetation restoration has exerted strong influences on regional climate, and provide useful information for the sustainable implementation of the GTG program.