全球冰—海洋耦合模式的海冰模拟

海冰是全球气候系统的重要分量,与大气和海洋的相互作用,直接影响大气环流和海洋环流,对气假及其变化及具有重要影响,文中依据冰、海洋间的热力、动力耦合相互作用,改进冰－海洋热力耦合方案,利用由中国科学院大气物理研究所的３０层海洋模式和基于Ｆｌａｔｏ空化流体流变学的海冰动力模式和Ｈｉｂｌｅｒ表面热收支平衡的零层少冰热力模式,建立全球冰－海洋耦合模式,利用大月平均气候资料,模拟的南半球少冰分布及海冰的分布及其季节性变化、海冰漂移进行了耦合模拟和分析,模拟的南半球海冰分布及季节变化与实际分析资料非常接近,比２０层冰－海洋耦合模式的结果有显著改进,北半球海冰范围偏小,但季节变化的量值与实际相当一致,模拟的海冰速度场反映了南、北半球海冰漂移的主要特征,如北极的穿极漂流和南大洋的绕极环流等,对海冰密集度的分析表明,模拟结果得以     

全球冰-海洋耦合模式的海冰模拟

海冰是全球气候系统的重要分量 ,与大气和海洋的相互作用 ,直接影响大气环流和海洋环流 ,对气候及其变化具有重要影响。文中依据冰、海洋间的热力、动力耦合相互作用 ,改进冰海洋热力耦合方案 ,利用由中国科学院大气物理研究所的 30层海洋模式和基于Flato空化流体流变学的海冰动力模式和Hibler表面热收支平衡的零层海冰热力模式 ,建立全球冰海洋耦合模式。利用大气月平均气候资料 ,利用冰海洋耦合模式对全球海冰的分布及其季节性变化、海冰漂移进行了耦合模拟和分析。模拟的南半球海冰分布及季节变化与实际分析资料非常接近 ,比 2 0层冰海洋耦合模式的结果有显著改进。北半球海冰范围偏小 ,但季节变化的量值与实际相当一致。模拟的海冰速度场反映了南、北半球海冰漂移的主要特征 ,如北极的穿极漂流和南大洋的绕极环流等。对海冰密集度的分析表明 ,模拟结果得以改进原因在于改进的冰海洋热力耦合方案增强了融冰期冰海洋耦合系统海洋热通量增加—密集度减小—能量收支增加的正反馈机制。     

大气水文模式耦合研究综述

首先阐明大气水文模式耦合的必要性，总结作为二者耦合的共同界面——陆面模式的发展过程。在此基础上，从耦合研究方法和目的出发，分4个类别详细论述当前国内外大气水文模式耦合研究的现状。指出了单向耦合不足和进行双向耦合所面临的几个关键问题包括：尺度问题、次网格分布非均匀性、降水模拟等。未来要求充分利用“3S”、四维变分同化等新技术和新方法，加强多学科的联合研究，深入开展大气水文模式的双向耦合试验和敏感性分析，研究大气—植被—土壤—水文系统的交互影响，从根本上提高大气和水文模式的模拟和预报水平。     

低纬大气热源与环流变异规律的研究

低纬大气热源与环流变异规律的研究南京大学大气科学系黄士松教授等在国家自然科学基金重点项目（批准号：４９１３５１２０）的资助下，开展了低纬大气环流变化的物理过程、低纬热源和热汇的时空变化规律及其与低纬环流关系、中国低纬环流区海气耦合模式的研制和试验等三...     

冻土过程参数化方案与中尺度大气模式的耦合

将发展的冻土过程参数化方案与耦合了NCARLSM陆面过程模式的中尺度大气模式MM5相耦合,对包括我国北方,蒙古国,东西伯利亚的高纬度地区进行了模拟.模拟时间选为北半球季节冻土生成的10月份.模拟结果表明,模式能够较好地模拟出该区域的冻土分布,并且对大气模式中海平面气压场、气温场的模拟改进显著.     

末次盛冰期太平洋赤道辐合带对暖池外热带海表温度变化的敏感性

利用美国NCAR CAM3大气环流模式,分析了末次盛冰期（LGM）两个不同的热带海表温度重建方案中,北半球冬季热带中、西太平洋对流活动及大气环流对暖池外（赤道东太平洋和热带大西洋）热带SST异常的敏感性。结果表明：  1）SST异常首先引起大气环流的改变。  赤道东太平洋对流层下沉增强,而作为经向补偿,副热带东太平洋上升运动增强,其中南半球尤为明显,同时南半球热带中、西太平洋上升运动增强,加剧了该区纬向逆时针环流,说明冰期热带海气耦合过程受气候背景场（如SST）影响很大;   2）大气环流格局改变引起热带中西太平洋的大气加热、对流活动、表层风场及降雨的巨大变化。  140°E以西的婆罗洲和菲律宾区域,总的大气加热减少是由于对流与辐射加热减少所致,对应于该区风场辐散和降雨减少;   而140°E以东的南半球热带中、西太平洋,大气吸收热量增加,对流与辐射加热均增强,总降雨量也随之增加,反映该区赤道辐合带南移并增强。该项研究为探索热带太平洋在冰期/间冰期旋回中的古海洋学变化提供了新的数据支撑。此外,不同重建SST对赤道辐合带的影响比较大,因此利用重建SST进行数值模拟或者利用耦合模式研究LGM热带海气相互作用时,应该十分重视全球热带SST分布特征。     

上层海洋-低层大气科学研究计划

海洋和大气是地球系统的重要组成部分，其在全球气候变化中具有重要作用。上层海洋与低层大气研究（SOLAS）作为IGBPII第一个新的核心计划，以海洋中深度在100 m以上的水层和 1 000 m以下的大气边界层为主要研究对象，通过多学科的交叉研究，以揭示海洋与大气相互作用的物理和生物地球化学过程耦合及其在气候变化中的作用。SOLAS科学计划得到了世界各国的积极响应，已有16个国家向国际SOLAS科学委员会提交了SOLAS进展状况的国家报告。我国也制定了自己的科学研究计划重点研究中国近海的大气物质入海、海洋温室气体排放、海-气界面上的物质和能量交换过程及其对气候和环境的影响和反馈。     

海洋碳循环模式的研究进展

从最简单的三箱模式开始简要回顾了海洋碳循环模式的发展历史，讨论了不同发展时期各种模式的特点，并指出了海洋吸收大气CO2的能力。近年来全球海洋环流碳循环模式经常使用简单生化过程，而在过程模式和一维模式中较详尽探讨生态系统在海洋碳循环的作用。最新的全球环流碳循模式估计海洋在20世纪80年代每年吸收大气CO2为1.5~2.2 GtC。还讨论了模拟海洋碳循环的现状和存在的问题。使用含显式生态系统的碳循环模式是研究CO2生物地球循环及其对全球变化响应的发展趋势。     

区域海气耦合模式研究进展

区域海气耦合模式是进行区域尺度气候模拟和预估的重要工具,近年来得到快速发展。在阐述区域海气耦合过程重要性的基础上,对当今国内外主要的区域海气耦合模式研究进展进行总结,归纳区域海气耦合模拟所关注的核心科学问题,介绍区域海气耦合模式的技术特点。发展基于耦合器且无通量订正的区域海气耦合模式是区域海气耦合模式发展的主流方向。当前国际上区域海气耦合模拟所关注的主要科学问题,包括区域海气耦合模式对区域海洋过程的模拟、区域海气耦合模式对区域大气过程的模拟、亚洲—西北太平洋季风模拟及其耦合模拟海表面温度(SST)冷偏差问题、热带海气相互作用过程模拟,以及区域海气耦合模式对未来气候变化的预估研究等。对上述5个方面科学问题的研究思路和主要科学结论进行总结,重点关注针对亚洲—西北太平洋季风区的区域海气耦合模拟研究,对区域海气耦合过程改进亚洲—西北太平洋地区降水模拟的物理机制,及在该区域模拟SST冷偏差的成因亦进行相关归纳和总结。最后提出当前区域海气耦合模拟亟待解决的关键科学问题。     

耦合冻土方案的大气模式对祁连山区春季土壤状况的模拟

对黑河流域上游山区水源涵养林区2003年春季土壤温度、湿度变化进行分析,运用耦合冻土参数化和没有耦合冻土参数化的大气模式MM5对该区春季过程进行了模拟,并与观测值进行对比,对模拟的产流量做了初步分析.结果显示:考虑冻土参数化方案对土壤温度模拟的改进主要体现在表层土壤,对深层土壤温度的模拟没有大的改进;考虑冻土参数化方案改进了对100 cm深度以内的土壤含水量的模拟,很大程度上缩小了模拟值与观测值之间的绝对误差.总体来讲,考虑了冻土参数化的模拟结果在一定程度上改进了模式对黑河流域上游季节冻土区土壤温、湿状况的模拟,在一定程度上逼近祁连山区的春季土壤状况.考虑冻土参数化和没有考虑冻土参数化对产流量的模拟表明,冻土参数化对产流量模拟有很大影响,冻土形成的不透水层可以产生更多的地表径流.尽管考虑冻土参数化过程对模拟结果有一定程度的改进,但模拟结果与实测结果还是有一定差距的.因此,进行寒区冻土过程模拟时,还需要进一步对土壤信息、模式物理过程,大气背景场驱动数据以及局地因素进行详细而精确的考虑,以期进一步提高模式在寒区的模拟性能,特别是为高寒山区无观测地带陆气相互作用研究提供依据.     

The relationship between intraseasonal tropical variability and ENSO and its modulation at seasonal to decadal timescales

The intraseasonal tropical variability (ITV) patterns in the tropical troposphere are documented using double space-time Fourier analysis. Madden and Julian oscillations (MJO) as well as equatorial coupled waves (Kelvin and Rossby) are investigated based on the NCEP/NCAR Reanalysis data for the 1977–2006 period and the outputs of an intermediate ocean-atmosphere coupled model named LODCA-OTCM. A strong seasonal dependence of the ITV/ENSO relationship is evidenced. The leading relationship for equatorial Rossby waves (with the correlation of the same order than for the MJO) is documented; namely, it is shown that intensification of Rossby waves in the central Pacific during boreal summer precedes by half a year the peak of El Niño. The fact that MJO activity in spring-summer is associated to the strength of subsequent El Niño is confirmed. It is shown that LODCA-QTCM is capable of simulating the convectively coupled equatorial waves in outgoing long wave radiation and zonal wind at 850 hPa fields with skill comparable to other Coupled General Circulation Models. The ITV/ENSO relationship is modulated at low frequency. In particular the periods of low ENSO amplitude are associated with weaker MJO activity and a cancellation of MJO at the ENSO development phase. In opposition, during the decaying phase, MJO signal is strong. The periods of strong ENSO activity are associated with a marked coupling between MJO, Kelvin and equatorially Rossby waves and ENSO; the precursor signal of MJO (Rossby waves) in the western (central) Pacific is obvious. The results provide material for the observed change in ENSO characteristics in recent years and question whether the characteristics of the ITV/ENSO relationship may be sensitive to the observed warming in the central tropical Pacific.     

A non-steady-state compartmental model of global-scale mercury biogeochemistry with interhemispheric atmospheric gradients

A box model of mercury (Hg) cycling between the atmosphere and ocean is described and used to estimate Hg fluxes on a global scale (The Global/Regional Interhemispheric Mercury Model, GRIMM). Unlike previous simulations of this system, few assumptions are made concerning the rate of prominent marine biogeochemical processes affecting Hg (e.g., evasion, particle scavenging, and deep ocean burial). Instead, consistency with two observed atmospheric distributions was required: the interhemispheric gradient in total atmospheric Hg and the value for changes in the deposition of Hg from the atmosphere since industrialization observed in both hemispheres. Sensitivity analyses underscore the importance to modeling of the atmospheric lifetime of Hg, the magnitude of the interhemispheric gradient, the historical changes in Hg concentrations of various reservoirs, and vertical exchange between the surface ocean and the permanent thermocline. Results of the model indicate: lower evasional fluxes of Hg from the global ocean than previous estimates; a prominent role for particle scavenging as a removal mechanism from the surface ocean; a modest influence of dry processes (dust and gas) on Hg removal from the atmosphere; and an estimate of natural land-based sources of Hg to the atmosphere that is no more than about half that of anthropogenic sources.     

Performance of general circulation models and their ensembles for the prediction of drought indices over India during summer monsoon

The drought during the months of June to September (JJAS) results in significant deficiency in the annual rainfall and affects the hydrological planning, disaster management, and the agriculture sector of India. Advance information on drought characteristics over the space may help in risk assessment over the country. This issue motivated the present study which deals with the prediction of drought during JJAS through standardized precipitation index (SPI) using nine general circulation models (GCM) product. Among these GCMs, three are the atmospheric and six are atmosphere–ocean coupled models. The performance of these GCM’s predicted SPI is examined against the observed SPI for the time period of 1982–2010. After a rigorous analysis, it can be concluded that the skill of prediction by GCM is not satisfactory, whereas the ability of the coupled models is better than the atmospheric models. An attempt has been made to improve the accuracy of predicted SPI using two different multi-model ensemble (MME) schemes, viz., arithmetic mean and weighted mean using singular value decomposition-based multiple linear regressions (SVD-MLR) of GCMs. It is found that among these MME techniques, SVD-MLR-based MME has more skill as compared to simple MME as well as individual GCMs.     

Methyl bromide: ocean sources, ocean sinks, and climate sensitivity

The oceans play an important role in the geochemical cycle of methyl bromide (CH3Br), the major carrier of O3-destroying bromine to the stratosphere. The quantity of CH3Br produced annually in seawater is comparable to the amount entering the atmosphere each year from natural and anthropogenic sources. The production mechanism is unknown but may be biological. Most of this CH3Br is consumed in situ by hydrolysis or reaction with chloride. The size of the fraction which escapes to the atmosphere is poorly constrained; measurements in seawater and the atmosphere have been used to justify both a large oceanic CH3Br flux to the atmosphere and a small net ocean sink. Since the consumption reactions are extremely temperature-sensitive, small temperature variations have large effects on the CH3Br concentration in seawater, and therefore on the exchange between the atmosphere and the ocean. The net CH3Br flux is also sensitive to variations in the rate of CH3Br production. We have quantified these effects using a simple steady state mass balance model. When CH3Br production rates are linearly scaled with seawater chlorophyll content, this model reproduces the latitudinal variations in marine CH3Br concentrations observed in the east Pacific Ocean by Singh et al. [1983] and by Lobert et al. [1995]. The apparent correlation of CH3Br production with primary production explains the discrepancies between the two observational studies, strengthening recent suggestions that the open ocean is a small net sink for atmospheric CH3Br, rather than a large net source. The Southern Ocean is implicated as a possible large net source of CH3Br to the atmosphere. Since our model indicates that both the direction and magnitude of CH3Br exchange between the atmosphere and ocean are extremely sensitive to temperature and marine productivity, and since the rate of CH3Br production in the oceans is comparable to the rate at which this compound is introduced to the atmosphere, even small perturbations to temperature or productivity can modify atmospheric CH3Br. Therefore atmospheric CH3Br should be sensitive to climate conditions. Our modeling indicates that climate-induced CH3Br variations can be larger than those resulting from small (+/- 25%) changes in the anthropogenic source, assuming that this source comprises less than half of all inputs. Future measurements of marine CH3Br, temperature, and primary production should be combined with such models to determine the relationship between marine biological activity and CH3Br production. Better understanding of the biological term is especially important to assess the importance of non-anthropogenic sources to stratospheric ozone loss and the sensitivity of these sources to global climate change.     

The role of the ocean feedback on Asian and African monsoon variations at 6 kyr and 9.5 kyr BP

The role of ocean feedback on monsoon variations at 6 and 9.5 kyr Before Present (BP) compared to present-day is investigated by using sets of simulations computed with the IPSL–CM4 ocean–atmosphere coupled model and simulations with the atmospheric model only with the SST prescribed to the present-day simulation for the coupled model. This work is complementary to the study by Marzin and Braconnot (2009) who have analyzed in detail the response of Indian and African monsoons to changes in insolation at 6 and 9.5 kyr BP using the IPSL–CM4 coupled model. The monsoon rainfall was intensified at 6 and 9.5 kyr BP compared to 0 kyr BP as a result of the intensified seasonal cycle of insolation in the Northern Hemisphere. In this paper, the impact of the ocean feedback is analysed for the Indian, East-Asian and African monsoons. The response of the ocean to the 6 and 9.5 kyr BP insolation forcing shares similarities between the two periods, but we highlight local differences and a delay in the response of the surface ocean between 6 and 9.5 kyr BP. The ocean feedback is shown to be positive for the early stage of the African monsoon. A dipole of SST in the tropical Atlantic favouring the earlier build-up of the monsoon in the 6 and 9.5 kyr BP coupled simulations. However, it is strongly negative for the Indian and East Asian monsoons, and of stronger amplitude at 9.5 than at 6 kyr BP over India. In these Asian regions, the convection is more active over the ocean than over the continent during the late monsoon season due to the ocean feedback. The results are consistent with previous studies about 6 kyr BP climate. In addition, it is shown that the ocean feedback is not sufficient to explain the relative amplifications of the different monsoon systems within the three periods of the Holocene, but that the mechanisms such as the effect of the precession on the seasonal cycle of monsoons as discussed in Marzin and Braconnot (2009) are more plausible.     

古海水pH值代用指标——海洋碳酸盐硼同位素研究进展

仪器测量的海水pH记录太短，无法评估海水pH自然变化的频率和幅度,并预测未来大气CO₂急剧增加后海水酸度的响应。海相碳酸盐的硼同位素是目前恢复古海洋pH的有效途径，倍受古气候—环境学家的重视。评述了近年来海洋碳酸盐的硼同位素的最新研究成果和研究现状，重点探讨了海相碳酸盐的硼同位素的测定方法、硼同位素—pH模型和古海水pH恢复等前沿内容，旨在提供一个系统的海洋碳酸盐硼同位素—pH系统的基本概念及研究思路，以利于气候学、地质学界了解这一交叉领域的发展动态。     

On the stability of a coupled ocean atmosphere system in the presence of wave-CISK

The stability of a simple coupled ocean-atmosphere system similar to the one studied by Hirst with general ocean thermodynamics is investigated in which the atmospheric heating is determined by sea surface temperature anomalies as well as the convergence feedback (low level moisture convergence by the waves themselves). It is shown that the unstable coupled mode found by Hirst (UH mode) is profoundly modified by the convergence feedback. The feedback increases the unstable range of the UH mode and can increase its growth rate several folds. The maximally growing UH mode can become westward propagating for certain strength of convergence feedback. If the convergence feedback strength exceeds a critical value, several new unstable intraseasonal modes are also introduced. These modes are basically ‘advective’ modes. For relatively weak strengths of the convergence feedback the growth rates of these modes are smaller than that of the UH mode. As the atmosphere approaches ‘moist neutral’ state, the growth rates of these modes could become comparable or even larger than that of the UH mode. It is argued that these results explain why the El Nino and Southern Oscillation (ENSO) signal is clear in the eastern Pacific but not so in the western Pacific and they may also explain some of the differences between individual ENSO events. Our results also explain the aperiodic behaviour of some coupled numerical models. Importance of this process in explaining the observed aperiodicity of the ENSO phenomenon is indicated.     

Advances in Studying the Sea-Air Dimethysulphide Exchange Process in the Southern Ocean

Dimethylsulphide (DMS) is an important marine biogenic gas and can be released into atmosphere through sea air gas exchange. The oxidants of DMS in atmosphere are the main compounds of pristine marine sulphate aerosols and would affect the global climate change finally. Almost all the atmospheric DMS, about 90%, comes from the ocean. The southern ocean, which consists about 20% of the whole ocean area, is one of the largest atmospheric DMS sources. In contrast with the other oceans, the Southern Ocean appears great spatial and temporal variability of surface seawater DMS. In addition, there are the complex hydrography system, variable sea ice condition and various biologic activities in the Southern Ocean as to make survey and understand DMS as well as its controlling factors most difficult. Moreover, it is significant to integrate the DMS sea ice exchange processes and its controlling factors studies. In order to develop survey and research on the sea air DMS exchange and biogeochemistry processes, estimate methods of the sea air DMS fluxes will be reviewed, characteristics of the spatial and temporal distribution of surface seawater DMS will be discussed and the sea air DMS flux in the Southern Ocean will be assessed. Finally, major controlling factors of DMS sea air DMS processes will also be analyzed.