CMIP3与CMIP5模式对中国西北干旱区气温和降水的模拟能力比较

Comparing Simulated Temperature and Precipitation of CMIP3 and CMIP5 in Arid Areas of Northwest China

通过对15组CMIP3和CMIP5两代模式集合平均对中国西北干旱区气温和降水的模拟能力比较,发现CMIP5模式对气温和降水的模拟更接近观测值。CMIP5模式模拟年、春季、夏季、秋季平均气温的相关系数比CMIP3模式分别提升了0.15、0.13、0.24和0.02,冬季下降了0.07。CMIP5模式对西北干旱区的平均气温变化趋势的模拟效果比CMIP3有所提高,对年、春季、夏季、秋季、冬季趋势的模拟偏差比CMIP3分别减少了0.03℃/10a、0.10℃/10a、0.01℃/10a、0.06℃/10a、0.14℃/10a。对西北干旱区平均气温年、季的模拟偏差分布上,CMIP5模式的偏差均比CMIP3低1~2℃。但是天山区年、季节平均气温的模拟与整体模拟偏低情况相反,CMIP3和CMIP5分别偏高3~6℃和1~4℃,对夏季的模拟偏高最严重,分别达到6℃和4℃。CMIP5模式整体对西北干旱区降水量的模拟结果与观测值的平均相关系数与CMIP3相差不大,均不超过0.1,而且偏差仍然较大。CMIP5模式对西北干旱区的降水量的变化趋势模拟效果比CMIP3有所降低,对年、春季、夏季、秋季、冬季趋势的模拟偏差比CMIP3增加了0.67 mm/10a、0.23mm/10a、0.51 mm/10a、0.11 mm/10a、0.14 mm/10a。CMIP5模式对年、春季、夏季、秋季和冬季的降水量模拟的均方根误差相比CMIP3分别减少77.6 mm、25.5 mm、25.0 mm、18.8 mm和13.9 mm。在空间上,CMIP5模式对年、季节降水模拟仍然偏高,但是比CMIP3有明显缓解;CMIP3和CMIP5模式对夏季天山区年降水量和夏季降水量的模拟也与大部分区域偏高的趋势明显相反,两代模式对夏季天山区的降水模拟均偏低50 mm左右。

The ensemble mean of simulated temperature and precipitation of CMIP5 and CMIP3 in arid areas of Northwest China was compared, the results showed that CMIP5 was more close to the observed value. Comparing with CMIP3, the correlation coeffcient of CMIP5 was improved by 0.15 for year, 0.13 in spring, 0.24 in summer and 0.02 in autumn, while decreased by 0.07 in winter. CMIP5 simulated better trend of mean temperature than CMIP3 in the arid area of Northwest China, the biases reduced by 0.03℃ per decade for year, 0.1℃ per decade for spring, 0.01℃per decade for summer, 0.06℃ per decade for autumn and 0.14℃ per decade for winter, respectively. The annual and seasonal bias of CMIP5 was 1-2℃ lower than CMIP3 in the arid area of Northwest China, but temperature for both CMIP3 and CMIP5 were 3-6℃ and 1-4℃ higher than observation in Tianshan Mountains, especially in summer, which was reached to 6℃ and 4℃, respectively. Two models showed little difference in the correlation coeffcient between simulated and observed precipitation, which was lower than 0.1, but the bias was still higher. The precision of precipitation trend for CMIP5 was lower than CMIP3, the biases increased by 0.67 mm per decade for year, 0.23 mm per decade for spring, 0.51 mm per decade for summer, 0.11 mm per decade for autumn, and 0.14 mm per decade for winter, respectively. The root mean square error of precipitation of CMIP5 was decreased by 77.6 mm, 25.5 mm, 25.0 mm, 18.8 mm and 13.9 mm for annual,spring, summer, autumn and winter, respectively. In spatial, CMIP5 still simulated higher annual and seasonal precipitation, but was better than CMIP3. Conversely, CMIP3 and CMIP5 gave lower annual and seasonal precipitation in the Tianshan Mountains, which was 50 mm lower than the observation.