厄尔尼诺衰减年东亚夏季大气环流和降水异常的耦合模式后报试验

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(LASG)新一代耦合气候模式(FGOALS)进行了气候异常季节后报试验,通过对1982—2005年7个个例的分析,探讨了厄尔尼诺衰减年夏季东亚大气环流和降水异常发生的物理机制。分析结果表明:FGOALS可以模拟出厄尔尼诺衰减年夏季相关气候场的异常态特征,表现为在西北太平洋为负海温异常,在热带印度洋为正海温异常,从而导致西北太平洋地区大气中低层异常反气旋环流的维持,其反气旋的西南部及西部的偏南及西南气流造成中国长江中下游地区降水的异常增多。在提前3—9个月的预测模拟中,模式可以模拟出气候场的异常演变,随着预测时间的延长,产生局地耦合的西北太平洋海表温度异常信号变弱,使得模拟出的西北太平洋反气旋异常偏弱、中心东移,从而导致影响东亚降水的气候场的异常变弱,降水异常区偏东。模拟结果也揭示出,西北太平洋海表温度负异常是厄尔尼诺异常信号的转换模态,并且,由于局地海-气相互作用,热带海温异常信号可以持续到第2年夏季,从而引起东亚大气环流和降水异常。对于东亚降水的季节预测出现误差可能是模式对ENSO的模拟偏差造成的,随着预测时间延长,模式模拟的厄尔尼诺信号偏弱,这将使得海表温度异常偏弱,同时相关物理场的异常响应也减弱。     

利用海气耦合模式模拟印度尼西亚贯穿流

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(LASG)发展的全球耦合气候系统模式(FGCM-1.0)100年数值模拟结果, 分析了模式模拟的印度尼西亚贯穿流(ITF)的平均态、季节变化和年际变化, 并且利用这些资料对ITF季节变化和年际变化的成因做了初步分析.模式模拟的ITF平均态、季节变化和年际变化同已有的观测结果相比是合理的, 经作者分析认为ITF的季节变化主要是因为印度尼西亚海域地处亚澳季风区, 海流对于季风的响应使得ITF发生季节变化; ITF的年际变化主要是因为热带环流的年际变化及其所导致的洋流调整造成的, 太平洋和印度洋都有影响.     

FGOALS－g快速耦合模式模拟的北太平洋年代际变率

本文分析了由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（LASG/IAP）最新发展的FGOALS_－g快速耦合模式300 a积分模拟结果,通过与多种观测资料的对比分析,讨论了北太平洋年代际变率的时空结构、主要年代际模态的演变特征以及与ENSO的联系等研究内容. 结果表明：该模式能成功模拟出北太平洋年代际变率的主要空间分布特征;模拟的年代际模态具有多时间尺度性,其中最显著的是周期约为10～20 a左右的准20年振荡模态,该模态上层海洋热容量异常的演变过程主要表现为大致沿副热带海洋涡旋做海盆尺度顺时针旋转的特征,相应的大气异常不仅与阿留申低压的变异有关,而且与太平洋-北美PNA）遥相关型以及上游的欧亚大气环流异常有密切关系;模拟的北太平洋年代际变率对年际ENSO循环的发生频率和强度有明显的调制作用. 但模拟的KOE区和阿拉斯加湾SST异常振幅比观测偏强,这与模式海冰偏多、高纬度SST偏冷的误差有关.     

FGOALS－g快速耦合模式模拟的北太平洋年代际变率

本文分析了由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（LASG/IAP）最新发展的FGOALS_－g快速耦合模式300 a积分模拟结果,通过与多种观测资料的对比分析,讨论了北太平洋年代际变率的时空结构、主要年代际模态的演变特征以及与ENSO的联系等研究内容. 结果表明：该模式能成功模拟出北太平洋年代际变率的主要空间分布特征;模拟的年代际模态具有多时间尺度性,其中最显著的是周期约为10～20 a左右的准20年振荡模态,该模态上层海洋热容量异常的演变过程主要表现为大致沿副热带海洋涡旋做海盆尺度顺时针旋转的特征,相应的大气异常不仅与阿留申低压的变异有关,而且与太平洋-北美PNA）遥相关型以及上游的欧亚大气环流异常有密切关系;模拟的北太平洋年代际变率对年际ENSO循环的发生频率和强度有明显的调制作用. 但模拟的KOE区和阿拉斯加湾SST异常振幅比观测偏强,这与模式海冰偏多、高纬度SST偏冷的误差有关.     

季节内振荡的数值模拟Ⅰ.模拟的自然变率

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 (LASG) 发展的耦合气候系统模式FGOALS 1.0_g控制试验 (二氧化碳浓度保持工业革命前的浓度不变, 代表无人类活动影响的自然变率) 模拟结果, 研究了模拟的自然变率下热带季节内振荡 (Intraseasonal Oscillation, 简称ISO) 的基本特征与年际、年代际变化.研究发现, 模拟的自然变率下全球ISO主要活跃区与近六十年的实测结果基本接近; ISO主要活跃区的季节变动特征与实际结果基本一致; 全球ISO强度冬强、夏弱的季节变化也与实际结果一致; 但模拟的ISO强度偏弱与ISO周期不明显.进一步利用控制试验模拟结果研究了模拟的自然变率下热带ISO特征的年际与年代际变化, 得出: 第一, 模拟的自然变率下的热带ISO强度存在明显的年际与年代际变化, 低强度指数阶段, 全球ISO强度减弱, 活跃区范围缩小, 高强度指数阶段则相反; 并存在季节性差异, 冬季不明显, 春秋季明显, 实测结果有类似结论, 但高、低指数似乎与增暖有关.第二, 模拟的自然变率下的热带东传或西传ISO能量比值总体来看基本上维持一种平衡状态, 不存在上升或下降趋势; 与实际状况下的东传相对能量增强、西传相对能量减弱趋势明显不同.     

大气季节内振荡的数值模拟 Ⅱ. 全球变暖的影响

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 (LASG)发展的耦合气候模式FGOALS1.0_g控制试验、二氧化碳 (CO2)浓度加倍试验模拟结果及实测结果 (NCEP/NCAR逐日再分析资料)研究了全球变暖对大气季节内振荡 (ISO)特征变化的影响.通过对比分析控制试验、二氧化碳浓度加倍试验模拟结果及观测结果发现: (1)FGOALS1.0_g耦合气候模式具有一定的模拟季节内振荡的能力, 主要表现为模式能够模拟出ISO活跃区的位置、中心位置的季节变动以及强度的季节变化, 其缺陷是模拟的ISO强度偏弱, 模拟的ISO周期不显著且偏高频; (2)实测资料诊断分析得到的近六十年来偏暖阶段ISO活跃区强度增强及范围扩大可能不是人类活动影响使温室气体增加所导致的, 它可能是大气ISO本身的年代际尺度变化; (3)近六十年来纬向东传波 (西传波)的能量的存在增长 (减少)趋势的主要原因可能是人类活动影响引起温室气体增加所导致的; (4)由于FGOALS1.0_g耦合气候模式在模拟ISO主周期及强度方面时存在不足, 因此实测结果诊断分析得到的偏暖阶段ISO小波能量强, 主周期范围大, 偏冷阶段反之的结论用FGOALS1.0_g耦合气候模式尚难以证实.     

The Flexible Global Ocean-Atmosphere-Land system model, Spectral Version 2: FGOALS-s2

The Flexible Global Ocean-Atmosphere-Land System model, Spectral Version 2 (FGOALS-s2) was used to simulate realistic climates and to study anthropogenic influences on climate change. Specifically, the FGOALS-s2 was integrated with Coupled Model Intercomparison Project Phase 5 (CMIP5) to conduct coordinated experiments that will provide valuable scientific information to climate research communities. The performances of FGOALS-s2 were assessed in simulating major climate phenomena, and documented both the strengths and weaknesses of the model. The results indicate that FGOALS-s2 successfully overcomes climate drift, and realistically models global and regional climate characteristics, including SST, precipitation, and atmospheric circulation. In particular, the model accurately captures annual and semi-annual SST cycles in the equatorial Pacific Ocean, and the main characteristic features of the Asian summer monsoon, which include a low-level southwestern jet and five monsoon rainfall centers. The simulated climate variability was further examined in terms of teleconnections, leading modes of global SST (namely, ENSO), Pacific Decadal Oscillations (PDO), and changes in 19th–20th century climate. The analysis demonstrates that FGOALS-s2 realistically simulates extra-tropical teleconnection patterns of large-scale climate, and irregular ENSO periods. The model gives fairly reasonable reconstructions of spatial patterns of PDO and global monsoon changes in the 20th century. However, because the indirect effects of aerosols are not included in the model, the simulated global temperature change during the period 1850–2005 is greater than the observed warming, by 0.6°C. Some other shortcomings of the model are also noted.     

Preliminary evaluations of FGOALS-g2 for decadal predictions

The Flexible Global Ocean-Atmosphere-Land System model, Grid-point Version 2 (FGOALS-g2) for decadal predictions, is evaluated preliminarily, based on sets of ensemble 10-year hindcasts that it has produced. The results show that the hindcasts were more accurate in decadal variability of SST and surface air temperature (SAT), particularly in that of Nin o3.4 SST and China regional SAT, than the second sample of the historical runs for 20th-century climate (the control) by the same model. Both the control and the hindcasts represented the global warming well using the same external forcings, but the control overestimated the warming. The hindcasts produced the warming closer to the observations. Performance of FGOALS-g2 in hindcasts benefits from more realistic initial conditions provided by the initialization run and a smaller model bias resulting from the use of a dynamic bias correction scheme newly developed in this study. The initialization consists of a 61-year nudging-based assimilation cycle, which follows on the control run on 01 January 1945 with the incorporation of observation data of upper-ocean temperature and salinity at each integration step in the ocean component model, the LASG IAP Climate System Ocean Model, Version 2 (LICOM2). The dynamic bias correction is implemented at each step of LICOM2 during the hindcasts to reduce the systematic biases existing in upper-ocean temperature and salinity by incorporating multi-year monthly mean increments produced in the assimilation cycle. The effectiveness of the assimilation cycle and the role of the correction scheme were assessed prior to the hindcasts.     

Long-term behaviors of two versions of FGOALS2 in preindustrial control simulations with implications for 20th century simulations

Climate drift in preindustrial control (PICTL) simulations can lead to spurious climate trends and large uncertainties in historical and future climate simulations in coupled models. This study examined the long-term behaviors and stabilities of the PICTL simulations in the two versions of FGOALS2 (the Flexible Global Ocean-Atmosphere-Land System model Version 2), which have been submitted to the Coupled Model Inter-comparison Project Phase 5 (CMIP5). As verified by examining time series of thermal fields and their linear trends, the PICTL simulations showed stable long-term integration behaviors and no obvious climate drift [the magnitudes of linear trends of SST were both less than 0.04oC (100 yr)-1] over multiple centuries. The changed SSTs in a century (that corresponded to the linear trends) were less than the standard deviations of annual mean values, which implied the internal variability was not affected. These trend values were less than 10% of those of global averaged SST from observations and historical runs during the periods of slow and rapid warming. Such stable long-term integration behaviors reduced the uncertainty of the estimation of global warming rates in the historical and future climate projections in the two versions of FGOALS2. Compared with the trends in the Northern Hemisphere, larger trends existed in the SST and sea ice extents at the middle to high latitudes of the Southern Hemisphere (SH). To estimate the historical and future climate trends in the SH or at some specific regions in FGOALS2, corrections needed to be carried out. The similar long-term behaviors in the two versions of FGOALS2 may be attributed to proper physical processes in the ocean model.     

热带太平洋和印度洋海面高度季节循环和年际变化的数值模拟

利用卫星海面高度计资料,分析了赤道太平洋和印度洋海面高度变化的季节和年际变化特征,并与一个耦合气候系统模式FGCM0模拟的海面高度进行比较,评估模式模拟海面高度季节和年际变化的能力.结果表明,尽管耦合模式存在一定的系统误差,但仍然能在相当程度上模拟出海面高度季节和年际变化的基本特征.同时为检验模式中印度尼西亚贯穿流(ITF)对海面高度季节和年际变化的影响,还进行了印度尼西亚海道完全关闭的敏感性试验,与控制试验结果对比表明,印度尼西亚贯穿流可以显著影响热带太平洋和印度洋年际变化的特征.