Indirect Radiative and Climatic Effects of Sulfate and Organic Carbon Aerosols over East Asia Investigated by RIEMS

The indirect radiative and climatic effects of sulfate and organic carbon aerosols over East Asia were investigated using a Regional Integrated Environment Model System (RIEMS) with an empirical aerosol-cloud parameterization.The first indirect radiative forcing was negative and ranged from-9-0 W m-2 in the domain.The maximum cooling,up to-9 W m-2,occurred in the Chongqing District in winter,whereas the cooling areas were larger during summer than in winter.Organic carbon (OC) aerosols were more abundant in winter than in summer,whereas the sulfate concentration during summer was much higher than during winter.The concentrations of sulfate and OC were comparable in winter,and sulfate played a dominant role in determining indirect radiative forcing in summer,whereas in winter,both sulfate and OC were important.The regional mean indirect radiative forcings were-0.73 W m-2 and-0.41 W m-2 in summer and winter,respectively.The surface cooling caused by indirect effects was more obvious in winter than that in summer.The ground temperature decreased by ～1.2 K in most areas of eastern China in winter,whereas in summer,the temperature decreased (～-1.5 K) in some regions,such as the Yangtze River region,but increased (～0.9 K) in the areas between the Yellow and Yangtze Rivers.In winter,the precipitation decreased by 0-6 mm in most areas of eastern China,but in summer,alternating bands of increasing (up to 80 mm) and decreasing (～-80 mm) precipitation appeared in eastern China.     

Influence of aerosol-radiative forcings on the diurnal and seasonal cycles of rainfall over West Africa and Eastern Atlantic Ocean using GCM simulations

Effects of aerosol radiative forcing on the diurnal and seasonal cycles of precipitation over West Africa and eastern Atlantic Ocean are investigated for the boreal summer season: June–July–August. An eight year (2000–2007) average of GCM simulated rainfall data is compared with the corresponding TRMM rainfall data. The comparison shows that the amplitude of the diurnal cycles of rainfall over land and ocean are reasonably well simulated. Over land, the phase of the simulated diurnal cycle of precipitation peaks several hours earlier than that of the TRMM data. Corresponding differences over the ocean(s) are relatively smaller. Some of the key features of the aerosol induced model simulated field anomalies are: (a) aerosol direct radiative forcing which increases the atmospheric stability and reduces the daytime moist convection and convective precipitation; (b) the aerosol induced changes in the diurnal cycle of precipitation are out of phase with those of the TRMM data over land, but are in-phase over the ocean; (c) aerosols reduce the amplitude of the diurnal cycle of precipitation over land and enhance it over ocean. However, the phase of the diurnal cycle is not affected much by the aerosol radiative forcing both over land and ocean. During the boreal summer, aerosol radiative forcing and induced circulation and precipitation cool the Sahel and the southern part of Sahara desert more than the adjacent areas to the north and south, thereby shifting the peak meridional temperature gradient northward. Consequently, an anomalous easterly jet is found north of its climatological location. This anomalous jet is associated with increased cyclonic circulation to the south of its axis, resulting in an anomalous monsoon rain belt in the Sahel.     

Simulation of the radiative effect of black carbon aerosols and the regional climate responses over China

As part of the development work of the Chinese new regional climate model (RIEMS), the radiative process of black carbon (BC) aerosols has been introduced into the original radiative procedures of RIEMS,and the transport model of BC aerosols has also been established and combined with the RIEMS model.Using the new model system, the distribution of black carbon aerosols and their radiative effect over the China region are investigated. The influences of BC aerosole on the atmospheric radiative transfer and on the air temperature, land surface temperature, and total rainfall are analyzed. It is found that BC aerosols induce a positive radiative forcing at the top of the atmosphere (TOA), which is dominated by shortwave radiative forcing. The maximum radiative forcing occurs in North China in July and in South China in April. At the same time, negative radiative forcing is observed on the surface. Based on the radiative forcing comparison between clear sky and cloudy sky, it is found that cloud can enforce the TOA positive radiative forcing and decrease the negative surface radiative forcing. The responses of the climate system in July to the radiative forcing due to BC aerosols are the decrease in the air temperature in the middle and lower reaches of the Changjiang River and Huaihe area and most areas of South China, and the weak increase or decrease in air temperature over North China. The total rainfall in the middle and lower reaches of the Changjiang River area is increased, but it decreased in North China in July.     

Direct Climatic Effect of Aerosols and Interdecadal Variations over East Asia Investigated by a Regional Coupled Climate-chemistry/aerosol Model

The direct climatic effect of aerosols for the 1980-2000 period over East Asia was numerically investigated by a regional scale coupled climate-chemistry/aerosol model,which includes major anthropogenic aerosols(sulfate,black carbon,and organic carbon) and natural aerosols(soil dust and sea salt) .Anthropogenic emissions used in model simulation are from a global emission inventory prepared for the Intergovernmental Panel on Climate Change Fifth Assessment Report(IPCC AR5) ,whereas natural aerosols are calculated online in the model.The simulated 20-year average direct solar radiative effect due to aerosols at the surface was estimated to be in a range of-9--33 W m-2 over most areas of China,with maxima over the Gobi desert of West China,and-12 W m-2 to-24 W m-2 over the Sichuan Basin,the middle and lower reaches of the Yellow River and the Yangtze River.Aerosols caused surface cooling in most areas of East Asia,with maxima of-0.8-C to-1.6-C over the deserts of West China,the Sichuan Basin,portions of central China,and the middle reaches of the Yangtze River. Aerosols induced a precipitation decrease over almost the entire East China,with maxima of-90 mm/year to-150 mm/year over the Sichuan Basin,the middle reaches of the Yangtze River and the lower reaches of the Yellow River.Interdecadal variation of the climate response to the aerosol direct radiative effect is evident,indicating larger decrease in surface air temperature and stronger perturbation to precipitation in the 1990s than that in the 1980s,which could be due to the interdecadal variation of anthropogenic emissions.     

中国区域气溶胶对东亚夏季风的可能影响(Ⅱ)：黑碳气溶胶及其与硫酸盐气溶胶的综合影响

利用NCAR的新一代GCM CAM3.0模式耦合一个气溶胶同化系统,研究了中国区域黑碳气溶胶的直接气候效应。结果显示,中国区域黑碳气溶胶引起全球平均辐射强迫为0.13 W/m2,导致除了青藏高原和广西以外的中国大部分地区降温,其中东北、四川和内蒙古中北部降温最显著。由此造成海陆温差缩小,气压差降低,从而总体上使东亚夏季风减弱。但与硫酸盐气溶胶的影响相比,黑碳气溶胶使季风减弱的程度较小,长江中下游地区的降水有所增加。黑碳气溶胶加强了中国东南部地区的对流活动,这与硫酸盐气溶胶的作用相反。同时,探讨了中国区域硫酸盐和黑碳气溶胶的综合直接气候效应。结果表明,硫酸盐和黑碳气溶胶的综合作用与仅有硫酸盐气溶胶的情形十分相似,降水变化的区域也和硫酸盐的保持一致。     

中国区域气溶胶对东亚夏季风的可能影响(Ⅱ)：黑碳气溶胶及其与硫酸盐气溶胶的综合影响

 利用NCAR的新一代GCM CAM3.0模式耦合一个气溶胶同化系统,研究了中国区域黑碳气溶胶的直接气候效应。结果显示,中国区域黑碳气溶胶引起全球平均辐射强迫为0.13 W/m2,导致除了青藏高原和广西以外的中国大部分地区降温,其中东北、四川和内蒙古中北部降温最显著。由此造成海陆温差缩小,气压差降低,从而总体上使东亚夏季风减弱。但与硫酸盐气溶胶的影响相比,黑碳气溶胶使季风减弱的程度较小,长江中下游地区的降水有所增加。黑碳气溶胶加强了中国东南部地区的对流活动,这与硫酸盐气溶胶的作用相反。同时,探讨了中国区域硫酸盐和黑碳气溶胶的综合直接气候效应。结果表明,硫酸盐和黑碳气溶胶的综合作用与仅有硫酸盐气溶胶的情形十分相似,降水变化的区域也和硫酸盐的保持一致。     

A modeling study of the effects of aerosols on clouds and precipitation over East Asia

The National Center for Atmospheric Research Community Atmosphere Model (version 3.5) coupled with the Morrison?CGettelman two-moment cloud microphysics scheme is employed to simulate the aerosol effects on clouds and precipitation in two numerical experiments, one representing present-day conditions (year?2000) and the other the pre-industrial conditions (year?1750) over East Asia by considering both direct and indirect aerosol effects. To isolate the aerosol effects, we used the same set of boundary conditions and only altered the aerosol emissions in both experiments. The simulated results show that the cloud microphysical properties are markedly affected by the increase in aerosols, especially for the column cloud droplet number concentration (DNC), liquid water path (LWP), and the cloud droplet effective radius (DER). With increased aerosols, DNC and LWP have been increased by 137% and 28%, respectively, while DER is reduced by 20%. Precipitation rates in East Asia and East China are reduced by 5.8% and 13%, respectively, by both the aerosol??s second indirect effect and the radiative forcing that enhanced atmospheric stability associated with the aerosol direct and first indirect effects. The significant reduction in summer precipitation in East Asia is also consistent with the weakening of the East Asian summer monsoon, resulting from the decreasing thermodynamic contrast between the Asian landmass and the surrounding oceans induced by the aerosol??s radiative effects. The increase in aerosols reduces the surface net shortwave radiative flux over the East Asia landmass, which leads to the reduction of the land surface temperature. With minimal changes in the sea surface temperature, hence, the weakening of the East Asian summer monsoon further enhances the reduction of summer precipitation over East Asia.     

近22 a人为气溶胶对东亚地区夏季风环流影响的数值模拟研究

运用区域气候模式RegCM3耦合入一个化学过程,对东亚地区三类人为排放气溶胶（硫酸盐、黑碳和有机碳）的时空分布特征及其对夏季风环流的影响进行了数值模拟研究。模拟结果显示,气溶胶的引入会引起东亚地区夏季850 hPa风场发生改变,我国江淮以东洋面上空出现了一个气旋式距平环流中心,中心以西的偏北风气流将削弱东亚地区夏季西南季风。通过讨论春季中国地区气溶胶浓度与夏季东亚地区850 hPa经向风的时滞关系,以及夏季中国地区气溶胶浓度与同期东亚地区850 hPa经向风的关系,可以发现,春、夏季中国地区气溶胶浓度均与夏季东亚地区850 hPa经向风有很好的负相关关系,当春季中国北方和夏季中国南方地区气溶胶浓度增加时,中国东部地区夏季偏南季风减弱。这可能与气溶胶改变了大气层顶和地表的辐射强迫,进而引起了海陆气压差异和位势高度场的变化有关。     

RegCM3引入气溶胶间接气候效应模拟效果对比

利用2006年区域气候模式RegCM3和Streets气溶胶排放源清单,在原模式中引入间接气候效应模块,改进云降水方案,对硫酸盐气溶胶的时空分布、辐射强迫效应进行了模拟研究。结果表明：硫酸盐气溶胶辐射强迫有明显季节变化;直接效应使地表温度降低,冬春季大值区出现在四川盆地,夏季大值区出现在华北平原。对降水的影响,主要表现在西南—东北水汽输送带上降水减少;其间接气候效应主要表现在使南方地区温度上升、北方地区温度下降;珠江流域和黄河流域降水减少,长江流域和东北地区降水增加。总的来说,直接效应大于间接效应。     

区域海气耦合模式模拟的2003年东亚夏季风季节内振荡

评估了一个区域海气耦合模式(由区域环境系统集成模式RIEMS和普林斯顿海洋模式POM组成)对2003年东亚夏季风季节内振荡(ISO)的模拟性能。通过与观测海温驱动单独大气模式结果的比较,分析了海气耦合过程对东亚夏季大气ISO模拟性能的影响。结果表明:耦合模式能够模拟出2003年中国东部地区夏季降水的气候态分布,模拟的中国东部尤其是江淮地区大气ISO活动较单独大气模式更为显著。同时,耦合模式能够较好地再现大气ISO经向上北传的传播特征,模拟的江淮流域降水处于活跃和中断期时西北太平洋地区低频降水和环流异常在强度和空间分布上较单独大气模式都更为合理。相比于单独大气模式,耦合模式对大气ISO模拟的改善,一方面与其对气候态西北太平洋副热带高压和相关对流层底层风场模拟的改善有关,另一方面与其包含海气相互作用,因而对低频降水与海温和水汽辐合位相关系模拟的改善有关。     

利用RIEMS-LRM对黄河河川径流的模拟研究

利用区域系统环境集成模式(RIEMS）和一个offline的大尺度汇流模型(LRM)对黄河的河川径流做了模拟。中国科学院大气物理所东亚中心从1991年开始建立和发展RIEMS，并验证RIEMS对东亚区域气候有较好的模拟能力。LRM是以线性时基不变假定为基础并能够计算水的水平传输的数学模型。RIEMS—LRM可以用来模拟和预测大尺度河流的河川径流。RIEMS—LRM在黄河上游河段的应用证实其有能力对大尺度河流的河川径流进行模拟。此外，作还分析了模拟误差产生的原因。     

区域气候模式与陆面模式的耦合及其对东亚气候模拟的影响

将大气—植被相互作用模式AVIM（Atmosphere-Vegetation Interaction Model）与区域环境系统集成模式 RIEMS2.0（Regional Integrated Environment Modeling System Version 2.0）耦合,利用耦合后的AVIM-RIEMS2.0模式在东亚区域选定典型年份进行积分试验,通过模拟结果与观测资料对比分析,从整体上评估耦合模式对东亚区域的模拟能力。结果表明:模式能够较好地模拟850 hPa风场、500 hPa位势高度、气温、降水以及地表热通量空间分布型和季节变化。双向耦合具有动态植被过程的AVIM模式后,RIEMS2.0模拟能力有一定程度的提高。850 hPa风场在冬季的中国东北、华北地区以及夏季的中国东部地区,模拟偏差都减小;500 hPa高度场模拟在中国北方地区改进明显,而在中国南方地区的夏季并没表现出明显的改进趋势。耦合模式改进了RIEMS2.0模式冬季气温模拟偏低而夏季偏高的现象。从区域平均看,耦合模式改善了降水模拟偏多的现象,并使得潜热通量的模拟效果有明显的改进,对感热通量模拟在大部分地区也有改进。总的来看,AVIM-RIEMS2.0耦合模式对中国北方地区模拟改进较为明显,而对中国南方地区,特别是华南地区没有明显的改进。     

Simulation of a Freezing Rain and Snow Storm Event over Southern China in January 2008 using RIEMS 2.0

The Regional Integrated Environmental Model System(RIEMS 2.0) with NCEP Reanalysis II is utilized to simulate the severe freezing rain and snow storm event over southern China in January 2008,which caused severe damage in the region.The relationships between the freezing rain process and the large-scale circulation,in terms of the westerly and low-level jets,water vapor transportation,and northerly wind area/intensity indices,were analyzed to understand the mechanisms of the freezing rain occurrence.The results indicate the following:(1) RIEMS 2.0 reproduced the pattern of precipitation in January 2008 well,especially for the temporal evolution of daily precipitation averaged over the Yangtze River valley and southern China;(2) RIEMS 2.0 reproduced the persistent trough in the South Branch of the westerlies,of which the southwesterly currents transported abundant moisture into southern China;(3) RIEMS 2.0 reasonably reproduced the pattern of frequencies of light and moderate rain,although it overestimated the frequency of rain in southern China.This study shows that RIEMS 2.0 can be feasibly applied to study extreme weather and climate events in East Asia.     

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。     

我国夏季降水与全球气温场的关系

用蒙特卡罗的相关方法研究我国夏季大尺度降水与全球气温场关系，发现我国夏季大尺度降水与全球气温场有密切相关，以同期相关为最密切；除与热带西太平洋、东太平洋等海域有密切相关外，还与欧洲东部、北美洲东北部以及东亚等内陆地区的不同季节气温场有关系。研究还表明，印度洋地区春季气温和北美洲北部及北太平洋西南部夏季气温偏高时，长江中下游夏季易涝。且它们与长江中下游夏季降水的相关均有阶段性，相关密切程度随时间有所增强。     

On the ability of the regional climate model RIEMS to simulate the present climate over Asia

A continuous 10-year simulation in Asia for the period of 1 July 1988 to 31 December 1998 was conducted using the Regional Integrated Environmental Model System (RIEMS) with NCEP Reanalysis II data as the driving fields. The model processes include surface physics state package (BATS 1e), a Holtslag explicit planetary boundary layer formulation, a Grell cumulus parameterization, and a modified radiation package (CCM3). Model-produced surface temperature and precipitation are compared with observations from 1001 meteorology stations distributed over Asia and with the 0.5 × 0.5 CRU gridded dataset. The analysis results show that: (1) RIEMS reproduces well the spatial pattern and the seasonal cycle of surface temperature and precipitation; (2) When regionally averaged, the seasonal mean temperature biases are within 1–2C. For precipitation, the model tends to give better simulation in winter than in summer, and seasonal precipitation biases are mostly in the range of ?12%–50%; (3) Spatial correlation coefficients between observed and simulated seasonal precipitation are higher in north of the Yangtze River than in the south and higher in winter than in summer; (4) RIEMS can well reproduce the spatial pattern of seasonal mean sea level pressure. In winter, the model-simulated Siberian high is stronger than the observed. In summer, the simulated subtropical high is shifted northwestwards; (5) The temporal evolution of the East Asia summer monsoon rain belt, with steady phases separated by more rapid transitions, is reproduced.     

澳大利亚东侧环流及海温异常与长江中下游夏季旱涝的关系

利用NCEP/NCAR再分析资料、NOAA的SST资料和1951～2005年中国160站月降水总量资料,研究了南极涛动,特别是澳大利亚东侧的环流及局地海温异常与长江中下游夏季旱涝的关系。研究发现,澳大利亚东侧位势高度异常与长江中下游夏季降水存在显著正相关,并由此定义了一个澳大利亚东侧位势高度指数（GHIEA）。当GHIEA指数偏大（小） 时,也即澳大利亚东侧位势高度偏高（偏低）,这种气压异常扰动可能通过Rossby波传播到北半球副热带地区,形成南北半球高度场的遥相关,使我国南海至菲律宾北部副热带地区位势高度增加（减小）,也即副高较强（弱）且偏南西伸（偏北偏东）,从而造成长江中下游地区降水偏多（少）。夏季南极涛动与长江中下游夏季降水的显著相关的原因主要是澳大利亚东侧局地位势高度异常造成的。澳大利亚东侧位势高度偏高（低）,南极涛动指数（IAO） 也随之偏大（小）,澳大利亚东侧位势高度异常通过南北半球高度场遥相关影响到北半球副热带地区的大气环流, 进而使长江中游夏季降水偏多（少）。另外,从局地海温异常角度也能部分解释澳大利亚东侧位势高度异常与长江中下游夏季降水存在显著正相关的可能成因:当澳大利亚东侧局地海域SST偏高（低）时,对应GHIEA指数偏高（低）,也即澳大利亚东侧位势高度偏高（低）。同时,当澳大利亚东侧局地海域SST偏高（低）时,南海地区SST也易于偏高（低）,使西太平洋副高较强并偏南西伸（较弱并偏北偏东）,从而造成长江中下游降水偏多（少）。     

2006年中国地区大气气溶胶浓度分布特征的模拟研究

结合2006年最新的气溶胶排放源资料,以NCEP/NCAR再分析资料为气象场,驱动大气化学传输模式MATCH（Model of Atmospheric Transport and Chemistry）,模拟了2006年中国地区硫酸盐、黑碳和沙尘气溶胶的质量浓度分布及其季节变化。模拟的气溶胶光学厚度（AOD）结果与CSHNET观测网数据比较分析后发现,基于21个观测站的61组月平均数据与相应模拟结果的相关系数为0.63。模拟结果表明：2006年中国地区硫酸盐气溶胶高值区主要分布在中国的四川盆地、华北及长江流域等工业较发达地区,而且具有明显的季节变化,四川盆地及长江以南地区,硫酸盐气溶胶1月份浓度高于7月份,长江以北的大部分地区,7月份浓度高于1月份;黑碳气溶胶主要分布在黄河、长江中下游地区及华南等地区,1月份浓度高于7月份;沙尘气溶胶主要分布在内蒙古中部沙漠地区,4月份浓度最高,7月份次之,其他月份较少。     

Direct Radiative Forcing and Climatic Effects of Aerosols over East Asia by RegCM3

The authors used a high-resolution regional climate model(RegCM3) coupled with a chemistry/aerosol module to simulate East Asian climate in 2006 and to test the climatic impacts of aerosols on regionalscale climate.The direct radiative forcing and climatic effects of aerosols(dust,sulfate,black carbon,and organic carbon) were discussed.The results indicated that aerosols generally produced negative radiative forcing at the top-of-the-atmosphere(TOA) over most areas of East Asia.The radiative forcing induced by aerosols exhibited significant seasonal and regional variations,with the strongest forcing occurring in summer.The aerosol feedbacks on surface air temperature and precipitation were clear.Surface cooling dominated features over the East Asian continental areas,which varied in the approximate range of-0.5 to-2°C with the maximum up to-3-C in summer over the deserts of West China.The aerosols induced complicated variations of precipitation.Except in summer,the rainfall generally varied in the range of-1 to 1 mm d-1 over most areas of China.     

Assessment of Individual Direct Radiative Effects of Major Aerosol Species in East Asia

To assess individual direct radiative effects of diverse aerosol species on a regional scale,the air quality modeling system RAMS-CMAQ(Regional Atmospheric Modeling System and Community Multiscale Air Quality) coupled with an aerosol optical properties/radiative transfer module was used to simulate the temporal and spatial distributions of their optical and radiative properties over East Asia throughout 2005.Annual and seasonal averaged aerosol direct radiative forcing(ADRF) of all important aerosols and individual components,such as sulfate,nitrate,ammonium,black carbon(BC),organic carbon(OC),and dust at top-of-atmosphere(TOA) in clear sky are analyzed.Analysis of the model results shows that the annual average ADRF of all important aerosols was in the range of 0 to-18 W m?2,with the maximum values mainly distributed over the Sichuan Basin.The direct radiative effects of sulfate,nitrate,and ammonium make up most of the total ADRF in East Asia,being concentrated mainly over North and Southeast China.The model domain is also divided into seven regions based on different administrative regions or countries to investigate detailed information about regional ADRF variations over East Asia.The model results show that the ADRFs of sulfate,ammonium,BC,and OC were stronger in summer and weaker in winter over most regions of East Asia,except over Southeast Asia.The seasonal variation in the ADRF of nitrate exhibited the opposite trend.A strong ADRF of dust mainly appeared in spring over Northwest China and Mongolia.