Influences of Climate Change on the Uptake and Storage of Anthropogenic CO2 in the Global Ocean

A global ocean general circulation model, called LASG/IAP Climate system ocean model (LICOM), is employed to study the influence of climate change on the uptake and storage of anthropogenic CO 2 in the global ocean. Two simulations were made: the control run (RUN1) with the climatological daily mean forcing data, and the climate change run (RUN2) with the interannually varying daily mean forcing data from the NCEP (National Centers for Environmental Prediction) of the US. The results show that the simulated distributions and storages of anthropogenic dissolved inorganic carbon (anDIC) from both runs are consistent with the data-based results. Compared with the data-based results, the simulations generate higher anDIC concentrations in the upper layer and lower storage amount of anDIC between the subsurface and 1000-m depth, especially in RUN1. A comparison of the two runs shows that the interannually varying forcing can enhance the transport of main water masses, so the rate of interior transport of anDIC is increased. The higher transfer rate of anDIC in RUN2 decreases its high concentration in the upper layer and increases its storage amount below the subsurface, which leads to closer distributions of anDIC in RUN2 to the data-based results than in RUN1. The higher transfer rate in RUN2 also induces larger exchange flux than in RUN1. It is estimated that the global oceanic anthropogenic CO 2 uptake was 1.83 and 2.16 Pg C yr 1 in the two runs in 1995, respectively, and as of 1994, the global ocean contained 99 Pg C in RUN1 and 107 Pg C in RUN2 of anDIC, indicating that the model under the interannually varying forcing could take up 8.1% more anthropogenic carbon than the model under the climatological forcing. These values are within the range of other estimates based on observation and model simulation, while the estimates in RUN1 are near the low bound of other works. It is estimated that the variability of root mean square of the global air-sea anthropogenic carbon flux from the simulated monthly mean results of RUN2 with its seasonal cycle and long-term trend removed is 0.1 Pg C yr 1 . The most distinct anomalies appear to be in the tropical Pacific Ocean and the Southern Ocean.     

Modeling of the Second Indirect Effect of Anthropogenic Aerosols in East Asia

This study investigated the second indirect climatic effect of anthropogenic aerosols,including sulfate,organic carbon(OC) ,and black carbon(BC) ,over East Asia.The seasonal variation of the climatic response to the second indirect effect was also characterized.The simulation period for this study was 2006.Due to a decrease in autoconversion rate from cloud water to rain as a result of aerosols,the cloud liquid water path(LWP) ,and radiative flux(RF) at the top of the atmosphere(TOA) changed dramatically,increasing by 14.3 g m-2 and decreasing by-4.1 W m-2 in terms of domain and annual average.Both LWP and RF changed most in autumn. There were strong decreases in ground temperature in Southwest China,the middle reaches of the Yangtze River in spring and autumn,while maximum cooling of up to-1.5 K occurred in the Chongqing district.The regional and annual mean change in ground temperature reached-0.2 K over eastern China.In all seasons except summer,precipitation generally decreased in most areas north of the Yangtze River,whereas precipitation changed little in South China.Precipitation changed most in summer,with alternating bands of increasing(～40 mm) and decreasing(～40 mm) precipitation appearing in eastern China.Precipitation decreased by 1.5-40 mm over large areas of Northeast China and the Huabei Plain.The domain and annual mean change in precipitation was approximately-0.3 mm over eastern China.The maximum reduction in precipitation occurred in summer,with mean absolute and relative changes of-1.2 mm and-3.8%over eastern China.This study revealed considerable climate responses to the second indirect effect of aerosols over specific regions of China.     

Numerical Study of the Effect of Anthropogenic Aerosols on Spring Persistent Rain over Eastern China

The eff ect of anthropogenic aerosols on the spring persistent rain （SPR） over eastern China is investigated by using a high-resolution Community Atmosphere Model version 5.1 （CAM5.1）. The results show that the SPR starts later due to anthropogenic aerosols, with a shortened duration and reduced rainfall amount. A reduction in air temperature over the low latitudes in East Asia is linked to anthropogenic aerosols;so is a weakened southwesterly on the north side of the subtropical high. Meanwhile, air temperature increases signifi cantly over the high latitudes. This north-south asymmetrical thermal eff ect acts to reduce the meridional temperature gradient, weakening the upper-level westerly jet over East Asia and the vertical motion over southeastern China. As a result, the SPR is reduced and has a much shorter duration. The indirect eff ect of anthropogenic aerosols also plays an important role in changing the SPR. Cloud droplet number concentration increases due to anthropogenic aerosols acting as cloud condensation nuclei, leading to a reduction in cloud eff ective radius over eastern China and a reduced precipitation effi ciency there.     

Responsibility for Past and Future Global Warming: Uncertainties in Attributing Anthropogenic Climate Change

During the negotiations on the Kyoto Protocol, Brazil proposed a methodology to link the relative contribution of Annex I Parties to emission reductions with the relative contributions of Parties to the global-mean temperature increase. The proposal was not adopted during the negotiations but referred to the Subsidiary Body for Scientific and Technological Advice for consideration of its methodological aspects. In this context we analyze the impact of model uncertainties and methodological choices on the regionally attributed global-mean temperature increase. A climate assessment model has been developed to calculate changes in greenhouse gas concentrations, global-mean temperature and sea-level rise attributable to individual regions. The analysis shows the impact of the different choices in methodological aspects to be as important as the impact of model uncertainties on a region's contribution to present and future global temperature increases. Choices may be the inclusion of the anthropogenic non-CO₂ greenhouse gas emissions and/or theCO₂ emissions associated with land-use changes. When responsibility to global temperature change is attributed to all emitting Parties, the impacts of modeling uncertainties and methodological choices on contributions of individual Parties are considerable. However, if relative contributions are calculated only within the group of Annex I countries, the results are less sensitive to the uncertainty aspects considered here.     

人为气溶胶的直接辐射效应及其对南亚冬季风的影响

运用区域气候模式RegCM4.0(Regional Climate Model Verson 4.0)耦合入一个化学过程,对硫酸盐、黑碳、有机碳这3种人为气溶胶的时空分布特征和直接辐射效应进行了数值模拟,进而研究了气溶胶对南亚冬季风的影响。结果表明:光学厚度和地表短波辐射强迫的时空变化可能主要受硫酸盐气溶胶的影响。在南亚夏季风向冬季风转换时期和南亚冬季风盛行时期,大气层顶和地表的负短波辐射强迫分布与气溶胶分布基本一致,地表辐射强迫强度绝对值比大气层顶辐射强迫强度绝对值大得多。相关分析和合成分析表明:在南亚夏季风向冬季风转换时期和南亚冬季风盛行时期,南亚人为气溶胶主要分布区中的气溶胶柱浓度含量与南亚冬季风的建立和强度有反相关关系。这与气溶胶吸收太阳辐射,从而引起气温和位势高度的变化有关。     

Modeling Study of the Effect of Anthropogenic Aerosols on Late Spring Drought in South China

In this study,the mechanisms underlying the decadal variability of late spring precipitation in South China are investigated by using the latest Community Earth System Model version 1 （CESM1）.We aim to unravel the effects of different climate forcing agents such as aerosols and greenhouse gases （GHGs） on the decadal variation of precipitation,based on transient experiments from pre-industry （for year 1850） to present-day （for year 2000）.Our results reveal that：（1） CESM1 can reproduce the climatological features of atmospheric circulation and precipitation for the late spring in South China; （2） only simulations including the forcing of anthropogenic aerosols can reproduce the observed decreasing trend of late spring precipitation from 1950-2000 in South China; （3） aerosols affect the decadal change of precipitation mainly by altering the large-scale atmospheric circulation,and to a less extent by increasing the lower-tropospheric stability to inhibit the convective precipitation; and （4） in comparison,other climate forcing agents such as GHGs have much smaller effects on the decadal change of spring precipitation in South China.     

Direct Radiative Forcing of Anthropogenic Aerosols over Oceans from Satellite Observations

Anthropogenic aerosols play an important role in the atmospheric energy balance. Anthropogenic aerosol optical depth (AOD) and its accompanying shortwave radiative forcing (RF) are usually simulated by nu- merical models. Recently, with the development of space-borne instruments and sophisticated retrieval algorithms, it has become possible to estimate aerosol radiative forcing based on satellite observations. In this study, we have estimated shortwave direct radiative forcing due to anthropogenic aerosols over oceans in all-sky conditions by combining clouds and the Single Scanner Footprint data of the Clouds and Earth’s Radiant Energy System (CERES/SSF) experiment, which provide measurements of upward shortwave fluxes at the top of atmosphere, with Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol and cloud products. We found that globally averaged aerosol radiative forcing over oceans in the clear-sky conditions and all-sky conditions were -1.03±0.48 W m-2 and -0.34 ±0.16 W m-2, respectively. Direct radiative forcing by anthropogenic aerosols shows large regional and seasonal variations. In some regions and in particular seasons, the magnitude of direct forcing by anthropogenic aerosols can be comparable to the forcing of greenhouse gases. However, it shows that aerosols caused the cooling effect, rather than warming effect from global scale, which is different from greenhouse gases.     

Comments on ``Direct Radiative Forcing of Anthropogenic Aerosols over Oceans from Satellite Observation"

Previous observational studies have estimated anthropogenic aerosol direct radiative forcing over oceans without due consideration of cloudy-sky aerosols.However,when interaction between clouds and aerosols located below or above the cloud level is taken into account,the aerosol direct radiative forcing is larger by as much as 5 W m-2 in most mid-latitude regions in the Northern Hemisphere.     

Estimation of the Distribution of Global Anthropogenic Heat Flux

The radiance lights data in 2006 from the National Oceanic and Atmospheric Administration Air Force Defense Meteorological Satellite Program/Operational Linescan System (DMSP/OLS) and authoritative energy data distributed by the United State Energy Information Administration were applied to estimate the global distribution of anthropogenic heat flux.A strong linear relationship was found to exist between the anthropogenic heat flux and the DMSP/OLS radiance data.On a global scale,the average value of anthropogenic heat flux is approximately 0.03 W m 2 and 0.10 W m 2 for global land area.The results indicate that global anthropogenic heat flux was geographically concentrated and distributed,fundamentally correlating to the economical activities.The anthropogenic heat flux concentrated in the economically developed areas including East Asia,Europe,and eastern North America.The anthropogenic heat flux in the concentrated regions,including the northeastern United States,Central Europe,United Kingdom,Japan,India,and East and South China is much larger than global average level,reaching a large enough value that could affect regional climate.In the center of the concentrated area,the anthropogenic heat flux density may exceed 100 W m 2,according to the results of the model.In developing areas,including South America,Central and North China,India,East Europe,and Middle East,the anthropogenic heat flux can reach a level of more than 10 W m 2 ;however,the anthropogenic heat flux in a vast area,including Africa,Central and North Asia,and South America,is low.With the development of global economy and urban agglomerations,the effect on climate of anthropogenic heat is essential for the research of climate change.     

基于干旱自然过程的干旱指数研究和应用

提出了"干旱自然过程"概念.取"干旱自然过程"长度、该过程和过程前60 d水份主要自然收支水平等要素综合成干旱指数,用逐步回归方法,按点、时段分别建立干旱预测模式群,采用非等权集成方法对模式集成,利用最优化理论,结合有关数学方法,求解了较优集成权重组合.结果表明,所得干旱指标与有关文献记载均吻合较好,模式集成效果良好,连续5 a试用均准确.     

Impacts of Internally and Externally Mixed Anthropogenic Sulfate and Carbonaceous Aerosols on East Asian Climate

A coupled regional climate and aerosol-chemistry model, RIEMS 2.0 (Regional Integrated Environmental Model System for Asia), in which anthropogenic sulfate, black carbon, and organic carbon were assumed to be externally mixed (EM), internally mixed (IM) or partially internally mixed (IEM), was used to simulate the impacts of these anthropogenic aerosols on East Asian climate for the entire year of 2006. The distributions of aerosol mass concentration, radiative forcing and hence the surface air temperature and precipitation variations under three mixing assumptions of aerosols were analyzed. The results indicated that the mass concentration of sulfate was sensitive to mixing assumptions, but carbonaceous aerosols were much less sensitive to the mixing types. Modeled results were compared with observations in a variety of sites in East Asia. It was found that the simulated concentrations of sulfate and carbonaceous aerosols were in accord with the observations in terms of magnitude. The simulated aerosol concentrations in IM case were closest to observation results. The regional average column burdens of sulfate, black carbon, and organic carbon, if internally mixed, were 11.49, 0.47, and 2.17 mg m⁻², respectively. The radiative forcing of anthropogenic aerosols at the top of the atmosphere increased from −1.27 (EM) to −1.97 W m⁻² (IM) while the normalized radiative forcing (NRF) decreased from −0.145 (EM) to −0.139 W mg⁻¹ (IM). The radiative forcing and NRF were −1.82 W m⁻² and −0.141 W mg⁻¹ for IEM, respectively. The surface air temperature changes over the domain due to the anthropogenic sulfate and carbonaceous aerosols were −0.067, −0.078, and −0.072 K, with maxima of −0.47, −0.50, and −0.49 K, for EM, IM, and IEM, respectively. Meanwhile, the annual precipitation variations were −8.0 (EM), −20.6 (IM), and −21.9 mm (IEM), with maxima of 148, 122, and 102 mm, respectively, indicating that the climate effects were stronger if the sulfate and carbonaceous aerosols were internally mixed.     

RCPs情景下中国北方地区干旱气候变化特征

利用水平分辨率为50 km×50 km的区域气候模式RegCM4,单向嵌套BCC_CSM1.1全球气候系统模式输出结果,以中国西北东部到华北地区为研究区域,对该区域的气候特征以及干旱趋势进行了预估。结果表明:(1)RegCM4模式对研究区域气温和降水的模拟能力可信度较高,能较好地模拟它们的空间分布特征及时间变化趋势,但由于模式存在一些系统性误差,因此部分区域模拟结果比实际略偏高。(2)2041—2050年相较于2006—2010年来讲,RCP4.5情景下研究区域气温将增加1.0℃左右,RCP8.5情景下增加约1.4℃;两种情景下研究区域降水表现为波动变化,一致性趋势不明显,但2041年以后均进入降水减少期。(3)总体来讲,两种情景下2041-2050年研究区域均可能出现较明显的干旱;RCP4.5情景下,夏、秋季2041—2050年干旱情况比前期严重,其中秋季从2042年开始,SPI值普遍偏低,有可能出现连旱现象;RCP8.5情景下,夏季干旱总体呈增加趋势,秋季则呈波动减少趋势,但2045年以后秋季又转为较干期。     

利用WRF-Chem模式模拟分析人为气溶胶对台风Fitow(1323)强度及降水的影响

利用气象与化学模块在线耦合的模式WRF-Chem V3.5(Weather Research and Forecasting Model coupled to Chemistry Version 3.5) 对1323号台风Fitow进行了模拟,设计无人为排放源、含人为排放源和人为排放源增加的三组模拟试验,对比分析了人为气溶胶对台风的影响。结果表明:人为气溶胶对台风移动路径影响较小。人为气溶胶增加,台风强度减弱,台风主体总累积降水量减少,靠近陆地阶段台风主体降水率减少。气溶胶的增多可提供更多的凝结核,台风外围云水增加,更多的云水可上升至冻结层以上形成过冷水,促进冰相粒子的形成,释放的潜热增加,使外围对流增强,降水增加。台风外围对流的发展,使低层入流的暖湿空气更多的在外围上升,向台风中心的入流减弱,眼墙的发展减弱,降水减少,台风强度减弱。台风外围的对流发展弱于眼墙的对流,降水仍以眼墙区为主,使累积降水量和降水率整体上表现为减少。     

Impact of Direct Radiative Forcing of Anthropogenic Aerosols on Diurnal Temperature Range in January in Eastern China

This study investigates the changes in January diurnal temperature range(DTR) in China during 1961-2000.The observed DTR changes during 1981-2000 relative to 1961-80 are first analyzed based on the daily temperature data at 546 weather stations.These observed DTR changes are classified into six cases depending on the changes in daily maximum and minimum temperatures,and then the occurrence frequency and magnitude of DTR change in each case are presented.Three transient simulations are then performed to understand the impact of greenhouse gases(GHGs) and aerosol direct forcing on DTR change:one without anthropogenic radiative forcing,one with anthropogenic GHGs,and another one with the combined forcing of GHGs and five species of anthropogenic aerosols.The predicted daily DTR changes during the years 1981-2000 are also classified into six cases and are compared with the observations.Results show that the previously proposed reason for DTR reduction,a stronger nocturnal warming than a daytime warming,explains only 19.8%of the observed DTR reduction days.DTR reductions are found to generally occur in northeastern China,coinciding with significant regional warming.The simulation with GHG forcing alone reproduces this type of DTR reduction with an occurrence frequency of 32.9%,which is larger than the observed value.Aerosol direct forcing reduces DTR mainly by daytime cooling.Consideration of aerosol cooling improves the simulation of occurrence frequencies of different types of DTR changes as compared to the simulation with GHGs alone,but it cannot improve the prediction of the magnitude of DTR changes.     

Characteristics of Anthropogenic Sulfate and Carbonaceous Aerosols over East Asia： Regional Modeling and Observation

The authors present spatial and temporal characteristics of anthropogenic sulfate and carbonaceous aerosols over East Asia using a 3-D coupled regional climate-chemistry-aerosol model, and compare the simulation with the limited aerosol observations over the region. The aerosol module consists of SO2, SO4^2-, hydrophobic and hydrophilic black carbon （BC） and organic carbon compounds （OC）, including emission, advections, dry and wet deposition, and chemical production and conversion. The simulated patterns of SO2 are closely tied to its emission rate, with sharp gradients between the highly polluted regions and more rural areas. Chemical conversion （especially in the aqueous phase） and dry deposition remove 60% and 30% of the total SO2 emission, respectively. The SO4^2- shows less horizontal gradient and seasonality than SO2, with wet deposition （60%） and export （27%） being two major sinks. Carbonaceous aerosols are spatially smoother than sulfur species. The aging process transforms more than 80% of hydrophobic BC and OC to hydrophilic components, which are removed by wet deposition （60%） and export （30%）. The simulated spatial and seasonal SO4^2-, BC and OC aerosol concentrations and total aerosol optical depth are generally consistent with the observations in rural areas over East Asia, with lower bias in simulated OC aerosols, likely due to the underestimation of anthropogenic OC emissions and missing treatment of secondary organic carbon. The results suggest that our model is a useful tool for characterizing the anthropogenic aerosol cycle and for assessing its potential climatic and environmental effects in future studies.     

对IPCC第五次评估报告气溶胶-云对气候变化影响与响应结论的解读

<正>在气候变化的驱动因子中,气溶胶和云对气候变化的影响程度仍然是不确定性最大的部分。政府间气候变化专门委员会(IPCC)第一工作组(WG1)第五次评估报告(AR5)总结了有关云和气溶胶对气候变化影响的研究,从观测、理论以及模式角度评估了其对气候变化的影响与响应~([1]),得出以下主要结论。     

Internal Variability as a Cause of Qualitative Intermodel Disagreement on Anthropogenic Climate Changes

Summary The qualitative agreement of two climate models, HADCM2 and ECHAM3, on the response of surface climate to anthropogenic climate forcing in the period 2020 – 2049 is studied. Special attention is paid to the role of internal climate variability as a source of intermodel disagreement. After illustrating the methods in an intermodel comparison of simulated changes in June–August mean precipitation, some global statistics are presented. Excluding surface air temperature, the four-season mean proportion of areas in which the two models agree on the sign of the climatic response is only 53 – 60% both for increases in CO₂ alone and for increases in CO₂ together with direct radiative forcing by sulphate aerosols, but somewhat larger, 59 – 70% for the separate aerosol effect. In areas where the response is strong (at least twice the standard error associated with internal variability) in both models, the agreement is better and the contrast between the different forcings becomes more marked. The proportion of agreement in such areas is 57 – 75% for the response to increases in CO₂ alone, 64 – 84% for the response to combined CO₂ and aerosol forcing, and as high as 88 – 94% for the separate aerosol effect. The relatively good intermodel agreement for aerosol-induced climate changes is suggested to be associated with the uneven horizontal distribution of aerosol forcing. Received December 2, 1998 Revised May 5, 1999     

A2和B2排放情景下气候变化对福建省水稻生产的阶段性影响

选择IPCC排放情景特别报告(SRES)中的A2和B2方案,利用区域气候模式PRECIS构建的气候变化情景文件与作物模型(CERES-Rice)耦合,采用雨养与灌溉两种方式,并综合考虑未来CO2浓度增加带来的直接增益效应,模拟了未来2020s及2040s两个时段气候变化对福建省水稻生育期与产量的影响。结果表明:无论是雨养方式还是灌溉方式,未来全省各稻区水稻生育期都将缩短,并且随着温度增高,2040s时段缩短的时间较2020s更长,单季稻生育期缩短时间最长,可达15~20 d。雨养条件下,除了闽东南双季稻区后季稻在2020s时段表现为2.3%(A2)和3.1%(B2)较小幅度的增产外,其他稻区各种稻作制度下的水稻产量较之BASE均出现了不同幅度的减产。闽西北稻区后季稻减产幅度最大,2020s时段A2和B2情景下减产幅度依次为6.9%和10.2%,2040s时段减产幅度进一步加大至14.1%和15.6%。闽东南稻区后季稻模拟结果较为乐观,尤其是在灌溉条件下表现为不同幅度的增产,两种情景下分别增产了1.7%、3.9%。双季稻种植区的后季稻产量稳定性均不如早稻和单季稻的,且随着温度升高,到2040s产量不稳定性有增加的趋势。灌溉在一定程度上可以缓解未来高温天气带来的产量波动。从全省的总产变化趋势来看,A2和B2两种排放情景模拟的结果都不容乐观,即使采用充分灌溉的方式,也依旧表现为减产。2020s时段,两种情景下分别减产0.74%与2.44%;2040s时段,两种情景下减产为3.50%与3.23%。未来早稻和单季稻生长季的土壤水分条件将变得不如目前湿润,与之相关的灌溉需要量均有所增加。     

Impacts of Climate Change on the Global Forest Sector

The path and magnitude of future anthropogenic emissions of carbon dioxide will likely influence changes in climate that may impact the global forest sector. These responses in the global forest sector may have implications for international efforts to stabilize the atmospheric concentration of carbon dioxide. This study takes a step toward including the role of global forest sector in integrated assessments of the global carbon cycle by linking global models of climate dynamics, ecosystem processes and forest economics to assess the potential responses of the global forest sector to different levels of greenhouse gas emissions. We utilize three climate scenarios and two economic scenarios to represent a range of greenhouse gas emissions and economic behavior. At the end of the analysis period (2040), the potential responses in regional forest growing stock simulated by the global ecosystem model range from decreases and increases for the low emissions climate scenario to increases in all regions for the high emissions climate scenario. The changes in vegetation are used to adjust timber supply in the softwood and hardwood sectors of the economic model. In general, the global changes in welfare are positive, but small across all scenarios. At the regional level, the changes in welfare can be large and either negative or positive. Markets and trade in forest products play important roles in whether a region realizes any gains associated with climate change. In general, regions with the lowest wood fiber production cost are able to expand harvests. Trade in forest products leads to lower prices elsewhere. The low-cost regions expand market shares and force higher-cost regions to decrease their harvests. Trade produces different economic gains and losses across the globe even though, globally, economic welfare increases. The results of this study indicate that assumptions within alternative climate scenarios and about trade in forest products are important factors that strongly influence the effects of climate change on the global forest sector.     

Estimates of Anthropogenic CO_2 Uptake in a Global Ocean Model

A global ocean general circulation model (L30T63) is employed to study the uptake and distribution of anthropogenic CO2 in the ocean. A subgrid-scale mixing scheme called GM90 is used in the model. There are two main GM90 parameters including isopycnal diffusivity and skew (thickness) diffusivity. Sensitivities of the ocean circulation and the redistribution of dissolved anthropogenic CO2 to these two parameters are examined. Two runs estimate the global oceanic anthropogenic CO2 uptake to be 1.64 and 1.73 ...