末次盛冰期东亚气候的成因检测

ATTRIBUTION OF EAST ASIAN CLIMATE AT THE LAST GLACIAL MAXIMUM

在国际古气候模拟比较计划设置的标准试验方案下，首先利用中国科学院大气物理研究所的全球大气环流模式（IAP—AGCM）模拟了末次盛冰期东亚气候状况，然后通过4组数值敏感性试验逐一模拟了大气CO2浓度、海洋表面温度（SST）和海冰、陆地冰盖和地形、东亚植被变化4项强迫因子的单独气候效应，进而对末次盛冰期东亚气候的成因进行了检测。结果表明，末次盛冰期除华南局部略有升温外，中国年均地表气温显著降低，降温幅度总体上向北增大，青藏高原处存在一个降温中心。其中，SST和海冰变化是华南局部略偏暖的主因，它同时导致了东亚其他区域地表气温的显著降低，特别是在东北亚地区；陆地冰盖和地形变化对于东亚地表气温的显著冷却作用主要体现在东亚的西北部；大气CO2浓度降低会引起东亚地区0．2—0．9℃的普遍降温；相对而言，东亚植被的降温作用（0．5—1．0℃）主要显现在中国40°N以南的区域。与此同时，SST和海冰变化能引起中国东部年均降水一定程度的减少，而大气CO2浓度、陆地冰盖和地形、东亚植被单独变化均不会显著影响东亚年均降水的分布状况，然而，上述四项因子的共同变化会通过协同作用引起中国东部年均降水的显著减少，西部地区降水则与现在差别不大。此外，末次盛冰期东亚夏季风的显著减弱源于SST和海冰变化，冬季风变化则可归因于SST和海冰、陆地冰盖和地形的变化。

According to the protocol of the phase one of the Paleoclimate Modelling Intercomparion Project （ PMIP）, a global atmospheric general circulation model developed at the Institute of Atmospheric Physics under the Chinese Academy of Sciences（IAP-AGCM） was used to simulate East Asian climate at the Last Glacial Maximum（LGM）, about 21,000 calendar years ago. Four sensitivity experiments were then performed to evaluate the individual climate effect of atmospheric CO2 concentration, sea surface temperature （SST）and sea ice, continental ice sheet and topography, and East Asian vegetation, respectively. It displays that glacial surface air temperature reduced strikingly over China, except for parts of South China. The surface cooling is generally featured by a larger magnitude towards high latitudes and a cooling maximum over the Tibetan Plateau. Attribution analysis reveals that the changes in SST and sea ice are mostly responsible for slight surface warming over parts of South China. They also cause notable surface cooling in the rest of East Asia, especially Northeast Asia. The changes in continental ice sheet and topography can give rise to surface cooling over northwestern East Asia. A uniform surface cooling of 0.2-0.9℃ in East Asia is induced by atmospheric CO2 concentration change. A statistically significant surface cooling due to East Asian vegetation change is only registered in China in south of about 40° N, with values of -0.5℃ to -1℃. The changes in SST and sea ice can lead to an annual precipitation reduction in eastern China to a certain extent. In contrast,annual precipitation change as respectively derived from each of the other three forcings is tiny. However, it is found out that the synergistic effects of the above four factors can reduce annual precipitation in eastern China greatly, although annual precipitation still remains similar to today in western China. Additionally, significant weaker-than-today East Asian summer monsoon at the LGM was resulted from the changes in SST and sea ice,and East Asian winter monsoon behaviors were due to the joint changes of SST and sea ice, and continental ice sheet and topography.