Could the Enhanced Forests Reduce Summer Warming in the Southern China?

Abstract

We examined if the enhanced forests could modify thermal climatic conditions in the southwestern China and its surrounding regions. We used the continuous time-series of annual forests fraction obtained from He et al. (2017) and sensible heat flux and temperatures from the European Center for Medium- Range Weather Forecasts reanalysis (ERA-Interim) for 1982-2011. In the linear regression trend analysis, the forests fraction, area-averaged over the southwestern China, significantly increased by 15.46% over the three decades. Significantly negative correlations of surface sensible heat flux during the summer growing season (June through August, JJA) with the area-averaged time-series of annual forests fraction were shown in the southwestern China. Correspondingly, the significantly negative correlations of JJA temperature at 925hPa with the annual forests fraction were observed in the southwestern China as well as the surrounding regions propagated to the east. The spatial patterns of negative correlations between the thermal climatic variables and forests fraction were consistent with the difference patterns of sensible heat flux and temperatures between high-fraction and low-fraction years of forests in the southwestern China. The results indicated that the enhanced forests in the southwestern China could reduce thermal energy transfer from land to atmosphere during JJA and, consequently, lower atmospheric temperatures. Based on the temperature trend analysis using the Chinese weather station data, we inferred that the forest-induced cooling effect might be one of the factors of relatively less summer warming, even cooling, trends in the southern China.