最新版海冰模式CICE的优势:基于北极海冰时空特征的评估

【研究目的】海冰模式CICE(Los Alamos sea ice model)作为当前国际上的主流海冰模式之一,已被耦合进了大部分地球系统模式,对该模式模拟能力的评估工作是发展地球系统模式的重要参考依据。【创新点】通过观测数据与不同版本CICE模式对北极海冰数值模拟结果进行对比分析,研究了最新版本CICE6.0模拟能力及优势。【重要结论】CICE6.0模拟结果的年际误差最小,且季节变化与观测值最为吻合。相较而言,CICE4.0严重高估了冬季海冰总面积及低估了夏季海冰总面积,而CICE5.0在冬季的误差明显大于其他版本。此外,我们也关注了三个模式对多年冰和季节冰的模拟效果,从其均方根误差空间分布看出:模拟误差主要出现在中央海区及其周边海域。CICE4.0和CICE5.0在这些区域模拟的多年冰偏少、季节冰偏多,均低估了多年冰的变化趋势,且高估了季节冰的变化趋势;CICE6.0很好地解决了这些问题,其模拟的多年冰和季节冰的趋势最接近观测值,特别在北冰洋中部。总的来说,CICE6.0模拟的北极海冰在各方面都优于其他版本。     

秋季区域海冰面积异常与冬季大气环流及东亚区域气候的关系

利用北极海冰面积资料和NCEP／NCAR再分析逐月高度场、风场资料以及中国160站气温资料，探讨秋季区域海冰异常与冬季大气环流及区域气候的关系，结果表明，秋季东西伯利亚海海冰的年际变化与北半球冬季大气环流及东亚冬季风有着密切的关系，秋季该海区海冰偏多（偏少），相应冬季东亚冬季风偏强（偏弱）；进一步分析发现秋季该海区海冰面积偏大（偏小），相应冬季中国大部地区气温明显偏低（偏高）。     

FGOALS_g1.1极地气候模拟

对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-g1.1的极地气候模拟现状进行了较为全面的评估。结果表明,FGOALS- g1.1对南北极海冰的主要分布特征、季节变化和年代际变化趋势具有一定的模拟能力。但也 注意到,与观测相比,模式存在以下几方面的问题：(1) 模拟的海冰总面积北极偏多,而南 极偏少。北极,北大西洋海冰全年明显偏多;夏季,西伯利亚沿海海冰偏多,而波弗特海 海冰偏少。南极,威德尔海和罗斯海冬季海冰偏少。南北极海冰边缘都存在异常的较大范 围密集度很小的碎冰区,夏季尤为显著。(2) 海冰流速在南北极海冰边缘和南极大陆沿岸附 近较大。北极,模式没能模拟出波弗特涡流,并且由于模式网格中北极点的处理问题,造成 其附近错误的海冰流场及厚度分布。这些海冰偏差与模式模拟的大气和海洋状况有着密切的 联系。进一步分析表明,FGOALS-g1.1模拟的冰岛低压和南极绕极西风带明显偏弱, 其通过大气环流和海表面风应力影响向极地的热量输送,在很大程度上导致上述的海冰偏差 。此外,耦合模式中大气-海冰-海洋的相互作用可以放大子模式中的偏差。     

FGOALS_gg1.1极地气候模拟

对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_g1.1的极地气候模拟现状进行了较为全面的评估.结果表明,FGOALS_g1.1对南北极海冰的主要分布特征、季节变化和年代际变化趋势具有一定的模拟能力.但也注意到,与观测相比,模式存在以下几方面的问题:(1)模拟的海冰总面积北极偏多,而南极偏少.北极,北大西洋海冰全年明显偏多;夏季,西伯利亚沿海海冰偏多,而波弗特海海冰偏少.南极,威德尔海和罗斯海冬季海冰偏少.南北极海冰边缘都存在异常的较大范围密集度很小的碎冰区,夏季尤为显著.(2)海冰流速在南北极海冰边缘和南极大陆沿岸附近较大.北极,模式没能模拟出波弗特涡流,并且由于模式网格中北极点的处理问题,造成其附近错误的海冰流场及厚度分布.这些海冰偏差与模式模拟的大气和海洋状况有着密切的联系.进一步分析表明,FGOALS_g1.1模拟的冰岛低压和南极绕极西风带明显偏弱,其通过大气环流和海表面风应力影响向极地的热量输送,在很大程度上导致上述的海冰偏差.此外,耦合模式中大气-海冰-海洋的相互作用可以放大子模式中的偏差.     

最新版海冰模式CICE的优势：基于北极海冰时空特征的评估（英文）

【研究目的】海冰模式CICE (Los Alamos sea ice model)作为当前国际上的主流海冰模式之一,已被耦合进了大部分地球系统模式,对该模式模拟能力的评估工作是发展地球系统模式的重要参考依据。【创新点】通过观测数据与不同版本CICE模式对北极海冰数值模拟结果进行对比分析,研究了最新版本CICE6.0模拟能力及优势。【重要结论】CICE6.0模拟结果的年际误差最小,且季节变化与观测值最为吻合。相较而言,CICE4.0严重高估了冬季海冰总面积及低估了夏季海冰总面积,而CICE5.0在冬季的误差明显大于其他版本。此外,我们也关注了三个模式对多年冰和季节冰的模拟效果,从其均方根误差空间分布看出:模拟误差主要出现在中央海区及其周边海域。CICE4.0和CICE5.0在这些区域模拟的多年冰偏少、季节冰偏多,均低估了多年冰的变化趋势,且高估了季节冰的变化趋势;CICE6.0很好地解决了这些问题,其模拟的多年冰和季节冰的趋势最接近观测值,特别在北冰洋中部。总的来说,CICE6.0模拟的北极海冰在各方面都优于其他版本。     

冬季戴维斯海峡的海冰面积年陈变化与东亚气候关系研究

采用北极1°×1°海冰面积指数、海平面气压、500hPa高度场和中国160站气温等资料,分析了戴维斯海峡海冰的年际变化与大气环流及东亚气候的关系,结果发现冬季戴维斯海峡是影响东亚以及北半球气候变化的关键区之一,该区海冰面积年际变化与500hPa高度场的WA型、EU型遥相关以及东亚冬季风强、弱之间存在密切的关系.冬季该区海冰偏多,则500hPa高度场在北大西洋戴维斯海峡西欧一带为WA型遥相关(美国东部高度场偏高,北美东北部到格陵兰一带高度场偏低),在欧亚大陆为出现EU型遥相关(贝加尔湖及其以东和西欧高度场偏高),西伯利亚高压减弱,致使东亚冬季风偏弱,我国东北、西北和华北地区偏暖;而冬季该区海冰偏少时,情况正好相反.     

CICE海冰模式中反照率相关参数对北极海冰模拟的影响

国家气候中心气候系统模式BCC_CSM2.0最新耦合了美国Los Alamos国家实验室发展的海冰模式CICE5.0,为试验模式中与反照率相关参数的敏感性及其对模拟结果的影响,提高模式对北极海冰的模拟能力,选取海冰模式中3个主要参数进行了敏感性试验。利用以BCC_CSM2.0耦合框架为基础建立的海冰-海洋耦合模式,选取CORE资料为大气强迫场开展试验,试验的3个参数分别为冰/雪表面反射率、雪粒半径和雪粒半径参考温度。结果表明,参数取值的不同对北极海冰的模拟有显著的影响,优化后的取值组合极大提高了模式的模拟能力,主要表现在:（1）改善了对北极冬季海冰厚度的模拟,海冰厚度增大,与观测资料更为吻合;（2）显著提高了对北极夏季海冰密集度的模拟能力,从而模拟的北极海冰范围年际循环与观测更为一致。参数取值的优化改进了模式对海冰反照率的模拟,进而影响了冰面短波辐射的吸收和海冰表层的融化,最终提高了模式对海冰密集度和厚度的模拟效果。      

CMIP5全球气候模式对中国地区降水模拟能力的评估

使用多种观测资料和43个参加耦合模式比较计划第五阶段（CMIP5）的全球气候模式模拟数据,评估分析了全球气候模式对中国地区1980-2005年降水特征的模拟能力。结果表明：多数CMIP5模式能够模拟出中国降水由西北向东南递增的分布特点,这与耦合模式比较计划第三阶段（CMIP3）的模式模拟结果类似,但华南地区降水模拟偏少,西部高原地区降水模拟偏多。模式能够较好地模拟出降水冬弱夏强的季节变化特征,但降水模拟系统性偏多。从EOF分析结果来看,多数CMIP5模式可以再现中国地区年平均降水的时空变化特征,集合平均的表现优于CMIP3。多模式集合在月、季、年时间尺度下模拟的平均值优于大部分单个模式的结果。CMIP5中6个中国模式的模拟能力与其他模式相当,其中FGOALS-g2、BCC-CSM1-1-m的模拟能力相对较好。     

不同区域气候模式对中国地区温度和降水的长期模拟比较

利用亚洲区域模式比较计划RMIP第二阶段五个区域模式和一个变网格全球模式，对中国地区1988年12月～1998年11月十年模拟的平均温度和降水结果，分析比较了不同区域气候模式对中国地区温度和降水的模拟能力。研究结果表明:几乎所有模式都能模拟出中国地区多年平均温度和降水的基本空间分布形态，但模式模拟的温度普遍偏低，在大部分区域，大多数模式模拟的降水偏多，而且不同模式之间存在较大差别。模式能较好地反映出中国地区温度的年际变化，对夏季降水的年际变化模拟较差，对冬季模拟较好。     

冬季戴维斯海峡的海冰面积年际变化与东亚气候关系研究

采用北极 1°× 1°海冰面积指数、海平面气压、50 0 h Pa高度场和中国 1 60站气温等资料 ,分析了戴维斯海峡海冰的年际变化与大气环流及东亚气候的关系 ,结果发现 :冬季戴维斯海峡是影响东亚以及北半球气候变化的关键区之一 ,该区海冰面积年际变化与 50 0 h Pa高度场的 WA型、EU型遥相关以及东亚冬季风强、弱之间存在密切的关系。冬季该区海冰偏多 ,则 50 0 h Pa高度场在北大西洋戴维斯海峡西欧一带为 WA型遥相关 (美国东部高度场偏高 ,北美东北部到格陵兰一带高度场偏低 ) ,在欧亚大陆为出现 EU型遥相关 (贝加尔湖及其以东和西欧高度场偏高 ) ,西伯利亚高压减弱 ,致使东亚冬季风偏弱 ,我国东北、西北和华北地区偏暖 ;而冬季该区海冰偏少时 ,情况正好相反。     

Mean climatic characteristics in high northern latitudes in an ocean-sea ice-atmosphere coupled model

Emphasizing the model‘s ability in mean climate reproduction in high northern latitudes, resultsfrom an ocean-sea ice-atmosphere coupled model are analyzed. It is shown that the coupled model cansimulate the main characteristics of annual mean global sea surface temperature and sea level pressurewell, but the extent of ice coverage produced in the Southern Hemisphere is not large enough. The maindistribution characteristics of simulated sea level pressure and temperature at 850 hPa in high northernlatitudes agree well with their counterparts in the NCEP reanalysis dataset, and the model can reproducethe Arctic Oscillation (AO) mode successfully. The simulated seasonal variation of sea ice in the NorthernHemisphere is rational and its main distribution features in winter agree well with those from observations.But the ice concentration in the sea ice edge area close to the Eurasian continent in the inner Arctic Oceanis much larger than the observation. There are significant interannual variation signals in the simulated seaice concentration in winter in high northern latitudes and the most significant area lies in the GreenlandSea, followed by the Barents Sea. All of these features agree well with the results from observations.     

Stratospheric climate and variability from a general circulation model and observations

The climate and natural variability of the large-scale stratospheric circulation simulated by a newly developed general circulation model are evaluated against available global observations. The simulation consisted of a 30-year annual cycle integration performed with a comprehensive model of the troposphere and stratosphere. The observations consisted of a 15-year dataset from global operational analyses of the troposphere and stratosphere. The model evaluation concentrates on the simulation of the evolution of the extratropical stratospheric circulation in both hemispheres. The December–February climatology of the observed zonal mean winter circulation is found to be reasonably well captured by the model, although in the Northern Hemisphere upper stratosphere the simulated westerly winds are systematically stronger and a cold bias is apparent in the polar stratosphere. This Northern Hemisphere stratospheric cold bias virtually disappears during spring (March–May), consistent with a realistic simulation of the spring weakening of the mean westerly winds in the model. A considerable amount of monthly interannual variability is also found in the simulation in the Northern Hemisphere in late winter and early spring. The simulated interannual variability is predominantly caused by polar warmings of the stratosphere, in agreement with observations. The breakdown of the Northern Hemisphere stratospheric polar vortex appears therefore to occur in a realistic way in the model. However, in early winter the model severely underestimates the interannual variability, especially in the upper troposphere. The Southern Hemisphere winter (June–August) zonal mean temperature is systematically colder in the model, and the simulated winds are somewhat too strong in the upper stratosphere. Contrary to the results for the Northern Hemisphere spring, this model cold bias worsens during the Southern Hemisphere spring (September–November). Significant discrepancies between the model results and the observations are therefore found during the breakdown of the Southern Hemisphere polar vortex. For instance, the simulated Southern Hemisphere stratosphere westerly jet continuously decreases in intensity more or less in situ from June to November, while the observed stratospheric jet moves downward and poleward.This paper was presented at the Third International Conference on Modelling of Global Climate Change and Variability, held in Hamburg 4–8 Sept. 1995 under the auspice of the Max Planck Institute for Meteorology, Hamburg. Editor for these papers is L. Dümenil.     

On the role of high latitude ice,snow, and vegetation feedbacks in the climatic response to external forcing changes

A seasonal energy balance climate model containing a detailed treatment of surface and planetary albedo, and in which seasonally varying land snow and sea ice amounts are simulated in terms of a number of explicit physical processes, is used to investigate the role of high latitude ice, snow, and vegetation feedback processes. Feedback processes are quantified by computing changes in radiative forcing and feedback factors associated with individual processes. Global sea ice albedo feedback is 5–8 times stronger than global land snowcover albedo feedback for a 2% solar constant increase or decrease, with Southern Hemisphere cryosphere feedback being 2–5 times stronger than Northern Hemisphere cryosphere feedback.In the absence of changes in ice extent, changes in ice thickness in response to an increase in solar constant are associated with an increase in summer surface melting which is exactly balanced by increased basal winter freezing, and a reduction in the upward ocean-air flux in summer which is exactly balanced by an increased flux in winter, with no change in the annual mean ocean-air flux. Changes in the mean annual ocean-air heat flux require changes in mean annual ice extent, and are constrained to equal the change in meridional oceanic heat flux convergence in equilibrium. Feedback between ice extent and the meridional oceanic heat flux obtained by scaling the oceanic heat diffusion coefficient by the ice-free fraction regulates the feedback between ice extent and mean annual air-sea heat fluxes in polar regions, and has a modest effect on model-simulated high latitude temperature change.Accounting for the partial masking effect of vegetation on snow-covered land reduces the Northern Hemisphere mean temperature response to a 2% solar constant decrease or increase by 20% and 10%, respectively, even though the radiative forcing change caused by land snowcover changes is about 3 times larger in the absence of vegetational masking. Two parameterizations of the tundra fraction are tested: one based on mean annual land air temperature, and the other based on July land air temperature. The enhancement of the mean Northern Hemisphere temperature response to solar constant changes when the forest-tundra ecotone is allowed to shift with climate is only 1/3 to 1/2 that obtained by Otterman et al. (1984) when the mean annual parameterization is used here, and only 1/4 to 1/3 as large using the July parameterization.The parameterized temperature dependence of ice and snow albedo is found to enhance the global mean temperature response to a 2% solar constant increase by only 0.04 °C, in sharp contrast to the results of Washington and Meehl (1986) obtained with a mean annual model. However, there are significant differences in the method used here and in Washington and Meehl to estimate the importance of this feedback process. When their approach is used in a mean annual version of the present model, closer agreement to their results is obtained.     

Evaluation of Surface Air Temperature Change over China and the Globe during the Twentieth Century in IAP AGCM4.0

Based on time series and linear trend analysis, the authors evaluated the performance of the fourth generation atmospheric general circulation model developed at the Institute of Atmospheric Physics, Chinese Academy of Sciences (IAP AGCM4.0), in simulating surface air temperature (SAT) during the twentieth century over China and the globe. The numerical experiment is conducted by driving the model with the observed sea surface temperature and sea ice. It is shown that IAP AGCM4.0 can simulate the warming trend of the global SAT, with the major warming regions in the high latitudes of the Northern Hemisphere and the mid-latitudes of the Southern Hemisphere. While the simulated trend over the whole globe is close to the observation, the model under-estimates the observed trend over the continents. More-over, the model simulates the spatial distribution of SAT in China, with a bias of approximately-2°C in eastern China, but with a more serious bias in western China. Compared with the global mean, however, the correlation coefficient between the simulation and observation in China is significantly lower, indicating that there is large uncertainty in simulating regional climate change.     

BCC_CSM对全球海表温度和混合层深度的模拟评估

为了定量评估北京气候中心(BCC)发展的BCC_CSM对当代全球海表温度和混合层深度的模拟能力,以WOA09(World Ocean Atlas 2009)观测资料作为检验模式的气候态实况场,提取包括BCC_CSM在内的CMIP5中的17个海气耦合模式的模拟结果,评估BCC_CSM模拟的全球海表温度和混合层深度的气候平均态并分析造成偏差的可能原因。结果表明:BCC_CSM模拟的海表温度在北半球中高纬的误差较大,而在其余纬度的模拟性能较佳。偏差的产生主要归因于海洋环流偏差。BCC_CSM模拟的最深混合层在北半球中高纬和南半球高纬地区的误差较大,同时这些区域也是多模式模拟差异最大的区域;其模拟的最浅混合层在南半球中高纬的偏差较大。冬季大西洋经向翻转环流的模拟在北大西洋下沉的位置偏南导致北半球高纬地区海表温度偏冷。由此认为包括BCC_CSM在内的许多海气耦合模式需重点改进对南、北半球深对流海域物理过程的描述,以提高气候预测的可信度。     

Climate links and recent extremes in antarctic sea ice, high-latitude cyclones, Southern Annular Mode and ENSO

In this article, we study the climate link between the Southern Annular Mode (SAM) and the southern sea-ice extent (SIE), and discuss the possible role of stationary waves and synoptic eddies in establishing this link. In doing so, we have used a combination of techniques involving spatial correlations of SIE, eddy streamfunction and wind anomalies, and statistics of high-latitude cyclone strength. It is suggested that stationary waves may be amplified by eddy anomalies associated with high latitude cyclones, resulting in more sea ice when the SAM is in its positive phase for most, but not all, longitudes. A similar association is observed during ENSO (La Ni?a years). Although this synergy in the SAM/ENSO response may partially reflect preferential areas for wave amplification around Antarctica, the short extent of the climate records does not allow for a definite causality connection to be established with SIE. Stronger polar cyclones are observed over the areas where the stationary waves are amplified. These deeper cyclones will break up and export ice equatorward more efficiently, but the near-coastal regions are cold enough to allow for a rapid re-freeze of the resulting ice break-up. We speculate that if global warming continues this same effect could help reverse the current (positive) Antarctic SIE trends once the ice gets thinner, similarly to what has been observed in the Northern Hemisphere.     

一个海洋-海冰耦合模式的北极气候模拟

This paper evaluates the simulation of Arctic sea ice states using an ocean-ice coupled model that employs LASG/IAP(the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics/the Institute of Atmospheric Physics) Climate Ocean Model(LICOM) and the sea-ice model from the Bergen Climate Model(BCM).It is shown that the coupled model can reasonably reproduce the major characteristics of the mean state,annual cycle,and interannual variability of the Arctic sea ice concentration.The coupled model also shows biases that were generally presented in other models,such as the underestimation of summer sea ice concentration and thickness as well as the unsatisfactory sea ice velocity.Sensitivity experiments indicate that the insufficient performance of the ocean model at high latitudes may be the main reason for the biases in the coupled model.The smoother and the fake "island",which had to be used due to the model’s grid in the North Pole region,likely caused the ocean model’s weak performance.Sea ice model thermodynamics are also responsible for the sea ice simulation biases.Therefore,both the thermodynamic module of the sea ice component and the model grid of the ocean component need to be further improved.     

耦合模式中潮汐对北大西洋模拟的影响研究

将8个主要平衡分潮加入到耦合模式中,对比研究潮汐对北大西洋模拟影响。由于潮汐的引入,模式模拟SST在北大西洋中纬度区域偏差显著减小,高纬度区域SST降温明显。SST模拟的改变使潮汐试验的海表净热通量模拟误差下降了约30%,但高纬度海冰显著增加。模式中引入潮汐对北大西洋上层环流,尤其是西边界流的路径模拟改进显著,这是SST及海表净热通量模拟改变的主要原因。同时,北大西洋上层和深层西边界流在潮汐的作用下,都表现出环流减弱的特点,这也使得大西洋经向翻转环流在26.5°N处上层2 km的输送减弱,与观测数据更为接近。较弱的大西洋经向翻转环流导致海洋热量在中低纬度聚集而无法输送到高纬度区域,这是造成潮汐试验模拟的海温在中低纬度偏高、高纬度偏低的原因,较弱的热输送也同时导致了潮汐试验中北半球海冰面积增加。     

BCC_CSM北极海冰模拟性能的改进对东亚冬季气候模拟的影响

国家气候中心气候系统模式(BCC_CSM)将美国Los Alamos国家实验室发展的海冰模式CICE5.0替代原有的海冰模式SIS,形成一个新版本耦合模式,很好地提高了模式对北极海冰和北极气候的模拟能力.在此基础上,本文评估新耦合模式对1985-2014年东亚冬季气候的模拟性能,检验北极海冰模拟性能的改进对东亚冬季气候...