气候系统模式FGOALS_gl模拟的小冰期气候

THE TRANSIENT SIMULATION OF LITTLE ICE AGE BY LASG/IAP CLIMATE SYSTEM MODEL FGOALS_gl

利用1650～1750年逐年变化的太阳辐照度等外强迫资料,驱动中国科学院大气物理研究所LASG发展的快速气候系统模式FGOALS_gl,模拟了小冰期(LIA)气候。把模拟的LIA表面温度变化与重建资料进行对比,结果表明FGOALS_gl对LIA气候具有较强的模拟能力,说明太阳辐照度的自然变化是导致小冰期气候的重要成因。模拟结果显示,LIA时期纬向平均温度变化表现为整个对流层降温,低纬度地区的降温中心位于对流层中层,北半球降温幅度大于南半球,高纬地区的降温幅度大于低纬地区。分析发现,中高纬地区的局地温度变化主要与环流异常相对应的冷暖平流有关;低纬地区的降温主要与赤道东风加强有关,东风增强通过增大蒸发和引起次表层冷海水上翻而令表层温度降低。LIA时期的降水变化主要位于中低纬地区,表现为日界线东(西)侧降水的负(正)异常。与降水异常相对应,Walker环流加强,东太平洋对流活动减弱,它与低纬地区对流层中层冷异常相联系。与大气层顶净短波辐射异常的季节变化相对应,南、北半球夏季平均表面温度异常较之冬季低0.28℃左右。

The LASG/IAP climate system model FGOALS_gl was run under transient external forcings from 1650A. D. to 1750A. D. to simulate the Little Ice Age （LIA）climate. Compared with the reconstruction data, the climate anomalies of LIA are reasonably reproduced by FGOALS_gl, demonstrating the dominant role of natural solar irradiance changes in resulting in the LIA climate. The cooling during the LIA penetrates throughout the troposphere and exhibits the maximum value in mid-troposphere at low latitudes. For surface air temperature, the cooling in the Northern Hemisphere is stronger than that in the Southern Hemisphere and is stronger at high latitudes than at low latitudes. Anomalous atmospheric circulation contributes to explain the regional surface air temperature anomalies in mid-high latitudes. In the tropical area, an intensified easterly is obtained in the model response which is consistent with a Southern-Oscillation-like structure in sea-level pressure. The enhanced easterly leads to a cooler sea surface temperature through intensified evaporation and upwelling of sub-surface cold water. The precipitation shows positive （negative）anomalies in the western （eastern）tropical Pacific. Associated with the precipitation anomalies, an intensified Walker circulation is simulated in the Eastern Pacific with suppressed convection. For both northern and southern hemispheres,the surface cooling is about 0.28℃ stronger in summer than in winter, which is consistent with the seasonal evolution of the net solar radiation changes at the top of atmosphere.