我国6ka BP植被变化的气候模拟研究

根据花粉恢复的古植被表面中国森林区的常绿阔叶,和叶阔叶林以及针叶林在6Ka BP向北扩张，反映了6ka BP夏季和冬季均比现代温暖的气候特征，然而，根据地球轨道参数变化驱动的气候模式，由于6kaBP时北半球夏季太阳辐射高于现代，而冬季太阳辐射低于现代，模拟的6ka BP夏季温度比规划温暖，但冬季比现代寒冷，模拟得出的冬季寒冷与地 冬季增温不一致，说明6ka BP的气候和植被变化并不完全受到太阳辐射变化的控制，针对这一重大缺陷，我们利用具有陆面过程的全球大气环流模型（ACCM＋SsiB)，采用了外动力太阳辐射变化和古地表状史的强迫边界场进行了古气候模拟试验，模拟结果能够捕捉到亚洲季风地区6kaBP冬季气候变暖的气候特征，初步阐明6ka BP植被变化的气候动力学机制。

CLIMATIC DYNAMICS FOR 6 kaBP VEGETATIONAL CHANGES IN ASIAN MONSOON REGION

Pollen-based reconstruction of palaeovegetation at 6 kaBP shows that the broad-leaved evergreen and deciduous forest zones as well as the mixed needle-leaved and deciduous forest zone expanded successively northwards to a large extent when compared with the present in China, suggesting a warmer-than-present winter and summer in China. However, the warming event during the 6 ka BP winter can not be proved on the basis of the orbit-forcing climate simulations at 6 ka BP because the simulations have witnessed a lower insolation than present in winter season in the low and middle latitudes of the Northern Hemisphere. This discrepancy indicates that the climatic dynamics can not be solely predicated by the orbit-forcing mechanism. A climate modeling with land processes (AGCM+SsiB) is thus used to explore the issues of the palaeoclimates. The simulation by the climate model with land surface processes as main factors can simulate the changes in temperature at 6 kaBP that increased both in summer and winter, and is in good agreement with pollen data. The preliminary results of the modeling demonstrated that land surface feedback in Asian monsoon region had played an important role.