全新世中期和末次冰盛期中国季风区面积和季风降水变化

Mid-Holocene and last glacial maximum changes in monsoon area and precipitation over China

使用国际古气候模拟比较计划第1~3阶段中共61个气候模式的数值试验结果,首先定量评估了它们对于当代中国年平均、夏季和冬季降水气候态的模拟能力,而后根据择优选取的26和16个气候模式分别对全新世中期和末次冰盛期中国季风区面积、季风降水以及季风降水强度变化进行了集中研究.结果表明：相对于参考时期,全新世中期中国季风区面积、季风降水及其强度分别在26,26和22个模式中模拟增加,平均增幅依次为10.7%,18.7%和7.3%,这主要是源于轨道强迫所导致的夏季经向温度梯度的减小以及夏季东亚与临近海域间热力对比的增大,海洋反馈的作用相对有限;上述模拟结果与季风区内的地质记录基本相符.在末次冰盛期,中国季风区面积和季风降水在15个模式中减小、季风降水强度在所有16个模式中减小,平均减幅依次为7.7%,25.1%和14.3%,夏季经向温度梯度的增加以及纬向和经向陆地和海洋间热力对比的减小是其内在动力学机制,海洋反馈有一定的抑制作用;以上模拟结果与季风区内较为有限的地质记录是定性一致的.

Sixty-one climate models participating in the Paleoclimate Modeling Intercomparison Project phases one （PMIP1） to three （PMIP3） were first evaluated in terms of their ability to reproduce the present annual, summer （May-September）, and winter （November-March） precipitation climatology of China. Changes in monsoon area （CMA）, monsoon precipitation （CMP）, and monsoon precipitation intensity （CMPI） over China were then investigated using the results of 26 and 16 reliable climate models for mid-Holocene （MH） and last glacial maximum （LGM）, respectively. Results show that relative to the reference period, the MH CMA, CMP, and CMPI consistently increased in 26, 26, and 22 models, respectively, with averages of 10.7% for CMA, 18.7% for CMP, and 7.3% for CMPI. Those changes were collectively attributable to an orbitally induced decrease in summer meridional temperature gradient and increases in summer land-sea thermal contrast between the East Asian continent and adjacent oceans. The role of the dynamic ocean was limited. Model results are generally consistent with geologic records over the monsoon regions in China. At the LGM, the CMA and CMP decreased in 15 models and the CMPI weakened in all 16 models, with averages of -7.7%, -25.1%, and -14.3%, respectively. In response to LGM forcing, the increase in summer rneridional temperature gradient and decreases in zonal and meridional land-sea thermal contrast were the underlying mechanisms, and interactive ocean had a suppression effect. The simulated changes agree qualitatively with most of the limited proxy data across the CMA.