Changes and Projection of Dry/Wet Areas over China

Based on the dry/wet index, the authors analyzed changes in dry/wet regions over China and projected their future change scenarios using CMIP5 (Coupled Model Intercomparison Project Phase 5) models. For the period of 1962-2011, the results show that the averages of extreme arid, arid, semi-arid, semi-humid, and humid regions account for 2.8%, 11.7%, 22.4%, 32.6%, and 30.5% of the land area of the country, respectively. The dry/wet index decreases overall and tends to become wet in the west and dry in the east. There is a significant contraction of humid and extreme arid regions but a significant expansion of semi-humid, semi-arid, and arid regions, indicating an increase in the climatically sensitive regions. The distribution of the change trend of dry/wet index during the spring and autumn resembles that of the annual mean, and the northwest tends to become dry during the winter while the southeast is becoming wet during the summer. Under the RCP4.5 (Representative Concentration Pathway 4.5) scenario, the median of the 18 CMIP5 models shows that, relative to the period of 1986-2005, annual precipitation would decrease only in the southeast, and the potential evapotranspiration would increase over the entire country, leading to dry/wet index decreases in most regions except the western part. The humid, arid, and extreme arid regions would reduce, while the opposite is true for the semi-arid and semi-humid regions.