Regional climate modeling

Similar to the projections of the temperature, two regional climate models RegCM2/CN with GG and GS scenarios and PRECIS with SRES A2 and B2 also have projected the precipitation changes over China and sub-regions for the 21st century. Both the models have consistently projected an increasing precipitation by about 10~14% in China for the late periods of the 21st century relative to 1961~1990 (see Table 10.9). Generally speaking, RegCM2/CN projects a larger increase in precipitation than that by PRECIS (see Table 10.9). But the patterns of the annual mean precipitation changes projected by the two regional models are quite different. The larger increase in precipitation of 0.5~1.5 mm/day for the late periods of the 21st century relative to 1961~1990 by PRECIS occurs over Southern China, North China and Tibetan Plateau. But RegCM2/CN projects more precipitation of 20~30% over Northwest and Northeast China, as well as some southern parts of South China. The drying regions are also very different, such as Hainan province, some parts of Guangdong, Sichuan and Jilin provinces by PRECIS; Hebei and Liaoning provinces, as well as some parts of Yangtze River valley by RegCM2/CN (Figures are not shown).

For seasonal precipitation changes, the two models have projected the larger increase in precipitation in four seasons of the late periods of the 21st century relative to 1961~1990 over China, North and South China, except for PRECIS over South China in the winter. A remarkable increase in precipitation by about 40~50% in Northwest China for winter might occur as projected by two models. The two models have projected another increase in precipitation by about 10~20% over Southern China in the summer and Northern China in the spring, respectively (see Fig.10.6).

Besides, based on the monthly mean precipitation projections over China by the RegCM2/CN with GG, most months might become wetter by 6~25% for the late periods of the 21st century than 1961~1990, especially for January and August. April and September might become drier by -4 ~ -7% than 1961~1990 (Figures are not shown).

Using the regional climate model RIEMS/GOALS, Zhang Yingjuang et al. (2006) studied the effect of CO2 gradual increasing on future precipitation change over China. The results can be found in 9.5.1

Table 10.9 PRECIS with SRES A2 and B2 projects the precipitation changes over China for the future three periods relative to 1961~1990 (Xu et al., 2005), in the bracket, RegCM2/CN with GG and GS (Gao et al., 2001) (unit: %)

Periods A2 B2

2011~2020 3 4

2041~2050 7 7

location

Fig. 10.6 RegCM2/CN and PRECIS project the annual and seasonal mean precipitation changes over China (C), Northern China (N) and Southern China (S) for the late periods of the 21st century relative to 1961~1990 (unit: %), light black is RegCM2/CN (Gao et al., 2001), heavy black is PRECIS (Xu et al., 2005)

location

Fig. 10.6 RegCM2/CN and PRECIS project the annual and seasonal mean precipitation changes over China (C), Northern China (N) and Southern China (S) for the late periods of the 21st century relative to 1961~1990 (unit: %), light black is RegCM2/CN (Gao et al., 2001), heavy black is PRECIS (Xu et al., 2005)

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