一个气候系统模式对小冰期外强迫变化的平衡态响应

The Equilibrium Response of LASG/IAP Climate System Model to Prescribed External Forcing during the Little Ice Age

本文利用中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室发展的气候系统模式FGOALS_gl,通过设定小冰期的太阳辐射变化,模拟了小冰期的气候平衡态,讨论了小冰期气候变化的机理。数值试验结果表明,由太阳辐照度变化和火山活动共同作用造成的太阳辐射减少是小冰期气候的重要成因,模拟的小冰期表层气温变化分布与重建资料在全球大多数地区较为一致。就全球平均情况而言,小冰期的年平均气温较之1860年偏冷0.15℃,较之20世纪平均情况偏冷0.6℃左右。小冰期温度变化存在显著的地域和季节特征,表现为北半球降温幅度大于南半球,高纬地区降温幅度大于低纬地区,夏季的降温幅度大于冬季。东亚地区小冰期温度较之1860年和20世纪分别偏冷0.3℃和0.6℃。小冰期的降水异常中心位于低纬地区,主要表现为赤道中东太平洋降水负异常和赤道中西太平洋降水正异常,以及位于热带印度洋的降水偶极子型。除欧洲和北美外,全球其他地区陆地降水均减少。东亚地区小冰期夏季降水的变化最为显著,较之1860年,华北、东北地区降水增加,而长江流域以南降水则减少;较之20世纪,东部降水异常表现出华北地区偏多、长江流域偏少、华南地区偏多的"三极型"分布特征。

This paper evaluates the performance of the fast coupled version of LASG/IAP climate system model FGOALS_gl on simulating the equilibrium state of the Little Ice Age （LIA） climate by giving prescribed external forcing.Analyses on the simulated temperature and precipitation demonstrate the following results：（1） Temperature：The cooling of near surface temperature during the LIA is reasonably reproduced by FGOALS_gl compared with the reconstruction data,indicating that the decrease of solar radiation plays a dominant role in the cooling during the LIA.The annual mean surface air temperature anomalies during the LIA are-0.15℃ and-0.6℃ with respect to the 1860 control run （1860CTL） and the 20th century simulation （20CW）.The surface cooling in the Northern Hemisphere is stronger than that in the Southern Hemisphere and is stronger at high latitudes than that at low latitudes.Analysis on the seasonal change suggests that the near surface temperature decrease in summer is stronger than that in winter.The annual mean temperature anomalies are-0.3℃ and-0.6℃ in East Asia with respect to 1860CTL and 20CW.（2） Precipitation：The precipitation in the LIA shows positive （negative） anomalies in the western （eastern） tropical Pacific and the ＂dipole pattern＂ in the tropical Indian Ocean.Global land precipitation shows negative anomalies except for Europe and North America.Precipitation change in East Asia is determined by summer precipitation.Compared with 1860CTL,the precipitation increases in North China and decreases in South China during summer,which increases in North China and South China and decreases along the Yangtze River valley with respect to 20CW.