MM5对中全新世时期中国地区气候的模拟研究

MM5 simulations of the China regional climate during the mid Holocene

中文关键词:  中全新世，中国地区，地球轨道参数，植被，大气环流背景场

英文关键词:Mid Holocene, China, Earth's orbital parameter, Vegetation, Large-scale circulation background field

中文摘要:

      MM5模式结果与地质记录的对比表明，这个模式系统可以较好地模拟中全新世时气候的变化，特别是模式模拟的降水变化与地质记录吻合得较好。区域模式的结果比全球模式结果有所改进。模式结果显示：与现代相比，中全新世时，中国地区的气温升高，夏季升温超过冬季。同时，中国的内蒙古东部地区、东北地区和华北地区降水显著增加；而中国的华东、华中、华南和西南地区降水减少。中国东部30°N以北地区夏季风增强；中国东部的冬季风减弱。从一系列敏感试验结果，可以发现：在中全新世时，中国地区的气温、风场和降水的变化主要受大尺度环流背景场变化的影响，其对降水变化的影响超过50%。其次受地表状况和植被变化的影响，植被的变化主要影响中国东部地区，使得在冬季和夏季中国地区均升温；而且，对华北部分地区降水变化的影响最大超过25%。地球轨道的变化使得中全新世时太阳辐射的季节变化较大，造成中全新世时中国地区在冬季降温，在夏季升温；同时，对东北和华北地区的降水有重要影响，其影响与植被变化的影响相当。中全新世时，大气中CO2的体积混合比为280×10-6，CO2的变化使得中全新世时气温降低，但量级较小。影响中全新世时中国地区气候变化的因子，按影响程度由大到小的排序为：大尺度环流背景场、植被变化、地球轨道参数变化和CO 2浓度变化。

英文摘要:

      Using a regional climate model MM5 nested with an atmospheric global climate model CCM3, a series of simulations and sensitivity experiments have been performed to investigate responses of the mid Holocene climate to different factors over China. Model simulations of the mid Holocene climate change, especially simulation of precipitation change, are in good agreement with the geologic records. Model results show that relative to the present day (PD) climate, the temperature over China increased in the mid-Holocene, and the increase in summer is more than that in winter. The summer monsoon strengthened over the eastern China north of 30°N, and the winter monsoon weakened over the whole eastern China; the precipitation increased over the west part of China, North China and Northeast China, and decreased over the south part of China. The sensitive experiments indicate that changes in the global climate (large-scale circulation background), vegetation, Earth's orbital parameter and CO 2 concentration led to the mid-Holocene climate change relative to the PD climate, and changes in precipitation, temperature and wind fields were mainly affected by change of the large-scale circulation background, especially with its effect on precipitation exceeding 50%. Changes in vegetation resulted in increasing of temperature in both winter and summer over China, especially over eastern China; furthermore, its effect on precipitation in North China accounts for 25% of the total change. Change in the orbital parameter produced the larger seasonal variation of solar radiation in the mid Holocene than the PD, which resulted in declining of temperature in winter and increasing in summer; and also had an important effect on precipitation with an effect equivalent to vegetation in Northeast China and North China. During the mid-Holocene, CO 2 content was only 280×10-6, which reduced temperature in a very small magnitude. Therefore, factors affecting the mid-Holocene climate change over China from strong to weak are large-scale circulation pattern, vegetation, Earth's orbital parameter and CO2 concentration.