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1.
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. 相似文献
2.
利用SBDART（Santa Barbara DISORT Atmospheric Radiative Transfer）辐射传输模式,结合AERONET（Aerosol Robotic Network）北京站观测的气溶胶光学特性数据,评估北京地区近十年气溶胶以及黑碳气溶胶的辐射强迫,主要研究结果如下:北京近十年气溶胶平均光学厚度（aerosol optical depth, AOD440nm）为0.61±0.56,?ngstr?m波长指数均值为1.09,单次散射反照率（single scattering albedo, SSA440nm）的均值为0.888±0.045;AOD呈现下降趋势,SSA呈上升趋势,表明该区域气溶胶污染有所改善。晴空条件下,大气层顶、地面和大气的气溶胶直接辐射强迫多年均值分别为?24.91±19.80 W m?2、?65.52±43.78 W m?2、40.61±28.62 W m?2,即气溶胶对大气层顶和地表为冷却效应,对大气产生加热作用。气溶胶和黑碳气溶胶的直接辐射强迫绝对值的年际变化表现为微弱的下降趋势,季节变化特征为春夏季高,冬季低,这与AOD的变化规律一致。并且黑碳气溶胶的直接辐射强迫下降趋势与SSA的上升趋势呈现较好的反位相关系。 相似文献
3.
不同污染条件下气溶胶对短波辐射通量影响的模拟研究 总被引：1，自引：0，他引：1
将高光谱分辨率的气溶胶光学参数化方案应用于高精度的辐射传输模式BCC_RAD（974带）中,研究不同污染状况下气溶胶在地表与近地层大气中造成的直接辐射强迫与辐射强迫效率。发现气溶胶在地表产生的直接辐射强迫为负,在近地层大气中产生的直接辐射强迫为正,且随气溶胶浓度的升高变大,说明大气气溶胶的含量越高,单位气溶胶光学厚度产生的直接辐射强迫越大。将短波划分为3个波段:紫外、可见光和近红外,发现在紫外、可见光和近红外波段中,不同污染状况下气溶胶在地表造成的直接辐射强迫范围分别为:-1.36—-13.66、-3.03—-32.41和-2.74—-28.62 W/m2,在近地层大气中产生的直接辐射强迫范围分别为0.44—4.26、0.99—9.80和0.93—8.87 W/m2。通过进一步对比自然和人为气溶胶的影响,发现人为气溶胶在地表和大气层顶产生的负直接辐射强迫以及对整层和近地面大气造成的正直接辐射强迫均大于自然气溶胶的影响,且上述两种排放源的气溶胶对整层大气辐射收支的影响主要集中在800 hPa高度以下的大气中。按照地表直接辐射强迫大小来分析不同种类气溶胶的影响,结果为硫酸盐>有机碳>黑碳>海盐>沙尘;按照近地层大气直接辐射强迫大小排序则为黑碳>有机碳>沙尘>海盐>硫酸盐。最后,通过分析散射型气溶胶与吸收型气溶胶对辐射通量的影响,还探究了大气中散射与吸收过程的异同。 相似文献
4.
西北地区气溶胶光学特性及辐射影响 总被引：3，自引：1，他引：2
利用SACOL（兰州大学半干旱气候与环境观测站）2006~2012年AERONET（全球气溶胶自动监测网）level 2.0和太阳短波辐射计资料,分析了中国西北地区气溶胶的光学特性与辐射影响。利用辐射传输模式SBDART（平面平行大气辐射传输模式）检验TOA（大气层顶）处辐射强迫为正的原因。BOA（地表）、TOA、Atmosphere（大气）的辐射强迫年均值分别是-59.43 W m-2、-17.03 W m-2、42.40 W m-2,AOD（光学厚度,550 nm）年均值0.37,α（波段的波长指数,440~675 nm）年均值0.91,变化趋势与AOD位相相反,当AOD为0.3~2.2时,α很小（0.0~0.2）,表明粒子尺度很大。SSA（单次散射反照率,675 nm）年均值0.93,g（不对称因子,675 nm）年均值0.68,复折射指数（675 nm）实部年均值1.48,虚部0.007。复折射指数实部的年变化趋势与AOD一致,虚部与AOD反位相,所以西北地区多为粗模态散射性气溶胶。气溶胶对大气的加热率最大值出现在0~2 km,随高度递减。冬、夏半年在地表加热率分别是2.6 K d-1和0.6 K d-1;季节变化中,冬季、秋季、春季和夏季,在地表的加热率依次是2.5 K d-1、1.4 K d-1、1.2 K d-1和0.2 K d-1,主要因为秋季气溶胶的吸收性大于春季。地表反照率和SSA对TOA正辐射强迫贡献率分别是22.5%和77.5%。 相似文献
5.
结合Cloud Sat对云的主动观测和MODIS(MODerate-Resolution Imaging Spectroradiometer)对气溶胶的被动反演,研究了典型站点气溶胶对云的宏观、微观和辐射特性的影响。结果表明,气溶胶对大陆性和海洋性站点的云均有显著影响。1)随气溶胶光学厚度(Aerosol Optical Depth,AOD)增加,水汽含量较弱站点的低层(高层)云量呈减小(增加)趋势,而水汽条件较强站点的各层云量均增大,且具有较高(较低)云顶的云层发生概率在各个站点都呈增加(减小)趋势。2)AOD的增大导致各站点云滴和冰晶粒子的有效半径均减小、大气层顶的短波和长波云辐射强迫均增强、短波云辐射强迫绝对值的加强更显著、长波云辐射强迫增加的幅度相对更大。3)气象要素在AOD大(小)值情况下的变化表明,大尺度动力条件并不能解释云的上述特性随AOD的显著改变。 相似文献
6.
Modeling Study of the Impact of Heterogeneous Reactions on Dust Surfaces on Aerosol Optical Depth and Direct Radiative Forcing over East Asia in Springtime 
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下载免费PDF全文 The spatial distributions and interannual variations of aerosol concentrations,aerosol optical depth(AOD) ,aerosol direct radiative forcings,and their responses to heterogeneous reactions on dust surfaces over East Asia in March 2006-10 were investigated by utilizing a regional coupled climate-chemistry/aerosol model. Anthropogenic aerosol concentrations(inorganic+carbonaceous) were higher in March 2006 and 2008,whereas soil dust reached its highest levels in March 2006 and 2010,resulting in stronger aerosol radiative forcings in these periods.The domain and five-year(2006-10) monthly mean concentrations of anthropogenic and dust aerosols,AOD,and radiative forcings at the surface(SURF) and at the top of the atmosphere(TOA) in March were 2.4μg m-3,13.1μg m-3,0.18,-19.0 W m-2,and-7.4 W m-2,respectively.Heterogeneous reactions led to an increase of total inorganic aerosol concentration;however,the ambient inorganic aerosol concentration decreased,resulting in a smaller AOD and weaker aerosol radiative forcings.In March 2006 and 2010,the changes in ambient inorganic aerosols,AOD,and aerosol radiative forcings were more evident.In terms of the domain and five-year averages,the total inorganic aerosol concentrations increased by 13.7%(0.17μg m-3) due to heterogeneous reactions,but the ambient inorganic aerosol concentrations were reduced by 10.5%(0.13μg m-3) .As a result,the changes in AOD,SURF and TOA radiative forcings were estimated to be-3.9%(-0.007) ,-1.7%(0.34 W m-2) ,and-4.3%(0.34 W m-2) ,respectively,in March over East Asia. 相似文献
7.
Muhammad Ali Salman Tariq Khalid Mahmood Asim Daud Adila Batool Zia-ul-Haq 《Asia-Pacific Journal of Atmospheric Sciences》2014,50(2):153-162
It is well established that aerosols affect the climate in a variety of ways. In order to understand these effects, we require an insight into the properties of aerosols. In this paper we present a study of aerosol properties such as aerosol optical depth (AOD), single scattering albedo (SSA) and aerosol radiative forcing (ARF) over mega city of Lahore (Pakistan). The data from Aerosol Robotic Network (AERONET) have been used for the period December 2009 to October 2011. The seasonal average values of AOD, asymmetry parameter (ASY) and volume size distribution in coarse mode were observed to be highest in summer. On the other hand, the average values of Angstrom exponent (AE) and imaginary part of refractive index (RI) were found to be maximum in winter. The average value of real part of RI was found to be higher in spring than in all other seasons. The SSA exhibited an increasing trend with wavelength in the range 440 nm–1020 nm in spring, summer and fall indicating the dominance of coarse particles (usually dust). However, a decreasing trend was found in winter in the range 675 nm–1020 nm pointing towards the dominance of biomass and urban/industrial aerosols. As far as aerosol radiative forcing (ARF) is concerned, we have found that during the spring season ARF was lowest at the surface of Earth and highest at top of the atmosphere (TOA). This indicates that the atmosphere was warmer in spring than in all the remaining seasons. 相似文献
8.
Yunfei FU Jiachen ZHU Yuanjian YANG Renmin YUAN Guosheng LIU Tao XIAN Peng LIU 《大气科学进展》2017,34(8):952-964
Taking winter and summer in eastern China as an example application, a grid-cell method of aerosol direct radiative forcing(ADRF) calculation is examined using the Santa Barbara DISORT Atmospheric Radiative Transfer(SBDART) model with inputs from MODIS and AERONET observations and reanalysis data. Results show that there are significant seasonal and regional differences in climatological mean aerosol optical parameters and ADRF. Higher aerosol optical depth(AOD)occurs in summer and two prominent high aerosol loading centers are observed. Higher single scattering albedo(SSA) in summer is likely associated with the weak absorbing secondary aerosols. SSA is higher in North China during summer but higher in South China during winter. Aerosols induce negative forcing at the top of the atmosphere(TOA) and surface during both winter and summer, which may be responsible for the decrease in temperature and the increase in relative humidity.Values of ADRF at the surface are four times stronger than those at the TOA. Both AOD and ADRF present strong interannual variations; however, their amplitudes are larger in summer. Moreover, patterns and trends of ADRF do not always correspond well to those of AOD. Differences in the spatial distributions of ADRF between strong and weak monsoon years are captured effectively. Generally, the present results justify that to calculate grid-cell ADRF at a large scale using the SBDART model with observational aerosol optical properties and reanalysis data is an effective approach. 相似文献
9.
中国东部气溶胶在天气尺度上的辐射强迫和对地面气温的影响 总被引：7，自引：0，他引：7
本文应用WRF-Chem(Weather Research and Forecasting—Chemistry)模式研究中国东部地区气溶胶及其部分组分(硫酸盐、硝酸盐和黑碳气溶胶)在天气尺度下的辐射强迫和对地面气温的影响。5个无明显降水时间段(2006年8月23～25日、2008年11月10～12日、2008年12月16～18日、2009年1月15～17日和2009年4月27～29日)的模拟显示,气溶胶浓度呈现显著的白天低,夜间高的日变化特征,且北方区域(29.8°～42.6°N,110.2°～120.3°E)平均PM2.5近地面浓度(40～80 μg m-3)高于南方区域(22.3°～29.9°N,109.7°～120.2°E,30～47 μg m-3)。气溶胶对地面2 m温度(地面气温)有明显的降温效果,在早上08:00(北京时,下同)和下午17:00左右最为显著,最高可降低约0.2～1 K,同时气溶胶的参与改善了模式对地面气温的模拟。本文还通过对2006年8月23～25日一次个例的模拟,定量分析了气溶胶及其部分组分(硫酸盐、硝酸盐和黑碳气溶胶)的总天气效应(直接效应+间接效应)、直接效应和间接效应分别对到达地面的短波辐射和地面气温的影响。北方区域平均气溶胶直接效应所造成的短波辐射强迫要高于南方区域,分别为-11.3 W m-2和-5.8 W m-2,导致地面气温分别降低了0.074 K和0.039 K。南方区域平均气溶胶间接效应所产的短波辐射强迫高于北方区域,分别为-14.4 W m-2和-12.4 W m-2,引起的地面气温的改变分别为-0.094 K和-0.035 K。对于气溶胶组分,硫酸盐气溶胶的直接效应和间接效应的作用相当,其总效应在北方和南方区域平均短波辐射强迫分别为-7.0 W m-2和-10.5 W m-2,对地面气温的影响为-0.062 K和-0.074 K,而硝酸盐气溶胶的作用略小。黑碳气溶胶使得北方和南方区域平均到达地表的太阳短波辐射分别减少了6.5 W m-2和5.8 W m-2,而地表气温则分别增加了0.053 K和0.017 K,相比于间接效应,黑碳气溶胶的直接效应的影响更加显著。 相似文献
10.
Direct Climatic Effect of Dust Aerosol in the NCAR Community Atmosphere Model Version 3 （CAM3） 总被引：3，自引：0，他引：3
Direct climate responses to dust shortwave and longwave radiative forcing (RF) are studied using the NCAR Community Atmosphere Model Version 3 (CAM3). The simulated RF at the top of the atmosphere (TOA) is-0.45 W m-2 in the solar spectrum and +0.09 W m-2 in the thermal spectrum on a global average. The magnitude of surface RF is larger than the TOA forcing, with global mean shortwave forcing of-1.76 W m-2 and longwave forcing of +0.31 W m-2 . As a result, dust aerosol causes the absorption of 1.1 W m-2 in t... 相似文献
11.
Atmospheric aerosols influence the earth's radiative balance directly through scattering and absorbing solar radiation, and indirectly through affecting cloud properties. An understanding of aerosol optical properties is fundamental to studies of aerosol effects on climate. Although many such studies have been undertaken, large uncertainties in describing aerosol optical characteristics remain, especially regarding the absorption properties of different aerosols. Aerosol radiative effects are considered as either positive or negative perturbations to the radiation balance, and they include direct, indirect (albedo effect and cloud lifetime effect), and semi-direct effects. The total direct effect of anthropogenic aerosols is negative (cooling), although some components may contribute a positive effect (warming). Both the albedo effect and cloud lifetime effect cool the atmosphere by increasing cloud optical depth and cloud cover, respectively. Absorbing aerosols, such as carbonaceous aerosols and dust, exert a positive forcing at the top of atmosphere and a negative forcing at the surface, and they can directly warm the atmosphere. Internally mixed black carbon aerosols produce a stronger warming effect than externally mixed black carbon particles do. The semi-direct effect of absorbing aerosols could amplify this warming effect. Based on observational (ground-and satellite-based) and simulation studies, this paper reviews current progress in research regarding the optical properties and radiative effects of aerosols and also discusses several important issues to be addressed in future studies. 相似文献
12.
基于国际大气化学-气候模式比较计划模式数据评估中国沙尘气溶胶直接辐射强迫 总被引：2，自引：0，他引：2
目前气候模式对沙尘气溶胶直接辐射强迫模拟仍有很大不确定性,多模式对比有助于定量评估不确定范围。国际大气化学—气候模式比较计划（Atmospheric Chemistry and Climate Model Intercomparison Project,ACCMIP）旨在评估当前模式对短寿命大气成分辐射强迫和气候效应的模拟能力。基于7个ACCMIP模式模拟的中国地区沙尘气溶胶浓度,我们评估了中国区域沙尘气溶胶直接辐射强迫和不确定性范围。结果显示,中国区域沙尘气溶胶年排放总量为215±163 Tg a-1,区域年均地表浓度为41±27 μg m-3,柱浓度为9±4 kg m-2,光学厚度为0.09±0.05。中国区域年均沙尘气溶胶产生的大气顶短波、长波和总辐射强迫分别为-1.3±0.8 W m-2、0.7±0.4 W m-2和-0.5±0.7 W m-2;地表短波、长波和总的辐射强迫值为-1.5±1.0 W m-2、1.8±0.9 W m-2和0.2±0.2 W m-2。沙尘气溶胶长波辐射强迫对沙尘浓度的垂直分布敏感。高层沙尘气溶胶浓度越大,其在大气顶产生更强的正值长波辐射强迫。然而,沙尘气溶胶短波辐射强迫主要受整层沙尘柱浓度控制,对沙尘浓度的垂直分布较不敏感。本文结果可为中国沙尘气溶胶的气候模拟提供参考。 相似文献
13.
The air quality model system RAMS (Regional Atmospheric Modeling System)-CMAQ (Models-3 Community Multi-scale Air Quality) coupled with an aerosol optical/radiative module was applied to investigate the impact of different aerosol mixing states (i.e., externally mixed, half externally and half internally mixed, and internally mixed) on radiative forcing in East Asia. The simulation results show that the aerosol optical depth (AOD) generally increased when the aerosol mixing state changed from externally mixed to internally mixed, while the single scattering albedo (SSA) decreased. Therefore, the scattering and absorption properties of aerosols can be significantly affected by the change of aerosol mixing states. Comparison of simulated and observed SSAs at five AERONET (Aerosol Robotic Network) sites suggests that SSA could be better estimated by considering aerosol particles to be internally mixed. Model analysis indicates that the impact of aerosol mixing state upon aerosol direct radiative forcing (DRF) is complex. Generally, the cooling effect of aerosols over East Asia are enhanced in the northern part of East Asia (Northern China, Korean peninsula, and the surrounding area of Japan) and are reduced in the southern part of East Asia (Sichuan Basin and Southeast China) by internal mixing process, and the variation range can reach 5 W m－2. The analysis shows that the internal mixing between inorganic salt and dust is likely the main reason that the cooling effect strengthens. Conversely, the internal mixture of anthropogenic aerosols, including sulfate, nitrate, ammonium, black carbon, and organic carbon, could obviously weaken the cooling effect. 相似文献
14.
黄土高原半干旱区典型日吸收性气溶胶综合观测分析 总被引：2，自引：0，他引：2
利用兰州大学半干旱气候与环境观测站的太阳光度计、激光雷达、微波辐射计综合观测资料,结合辐射传输模式分析了该地区秋季典型日2012年9月3~4日、21日和28日气溶胶物理特性、垂直分布特征,及其与气象条件的关系。研究时期的气溶胶主要为局地沙尘与人为污染混合气溶胶,吸收性明显,尺度较小。其中,4日西北风增强,远距离传输沙尘气溶胶,气溶胶光学厚度最大,粒子尺度明显增大。尝试利用灰色关联度法确定参考高度,分别为7.41 km、8.47 km、7.13 km和7.66 km,反演气溶胶消光系数,由此积分得到的光学厚度与太阳光度计观测值相关性可达0.975,反演效果较好。研究时期气溶胶的抬升主要受白天热力湍流作用,边界层发展,气溶胶向上传输,每日12时（当地时间,下同）至14时传输至最大高度,气溶胶抬升的高度对应大气加热率的高值区,低层加热率可达1 K d-1。气溶胶在大气层顶和地面造成负辐射强迫,分别为-12.707 W m-2、-25.398 W m-2,大气中表现为正辐射强迫,为12.692 W m-2,大气层顶的辐射强迫对气溶胶的物理特性最为敏感,当气溶胶吸收性明显时,大气层顶的瞬时辐射强迫会出现正值。 相似文献
15.
Hyein Park Chul E. Chung Annica M. L. Ekman Jung-Ok Choi 《Asia-Pacific Journal of Atmospheric Sciences》2014,50(3):377-390
This study examines and evaluates simulated aerosol optical depth (AOD) and fine-mode AOD (fAOD) from the ACCMIP and CMIP5 global model archives. Satellite data nudged to AERONET data are used to construct reliable global observations of AOD and fAOD for validating the simulations. The difference in simulated global average AOD among models is of the order of a factor of 2, and the difference is even larger (～factor of 3) for fAOD. Compared to the observations, the models tend to underestimate AOD and fAOD significantly over eastern China. Another important discrepancy is that the models show larger fAOD over the Indus-Ganga Plain in summer than in winter, whereas the observations display an opposite feature. The models also overestimate the fAOD over the biomass burning regions of central Africa in DJF and underestimate the fAOD over the biomass burning regions of southern Africa in JJA. To evaluate the effect of the discrepancy between modeled and observed fAOD on aerosol direct radiative forcing, an offline radiation model is utilized. Comparing the model-fAODderived fine-mode forcing with the fine-mode forcing derived from the fAOD observation, the models tend to give too large (negative) value. This result implies that the calculated anthropogenic aerosol forcing in ACCMIP and CMIP5 models has a negative bias. 相似文献
16.
Data on aerosol optical thickness(AOT) and single scattering albedo(SSA) derived from Moderate Resolution Imaging Spectrometer(MODIS) and Ozone Monitoring Instrument(OMI) measurements,respectively,are used jointly to examine the seasonal variations of aerosols over East Asia.The seasonal signals of the total AOT are well defined and nearly similar over the land and over the ocean.These findings indicate a natural cycle of aerosols that originate primarily from natural emissions. In contrast,the small-sized aerosols represented by the fine-mode AOT,which are primarily generated over the land by human activities,do not have evident seasonalscale fluctuations.A persistent maximum of aerosol loadings centered over the Sichuan basin is associated with considerable amounts of fine-mode aerosols throughout the year.Most regions exhibit a general spring maximum. During the summer,however,the aerosol loadings are the most marked over north central China.This occurrence may result from anthropogenic fine particles,such as sulfate and nitrate.Four typical regions were selected to perform a covariation analysis of the monthly gridded AOT and SSA.Over southwestern and southeastern China,if the aerosol loadings are small to moderate they are composed primarily of the highly absorptive aerosols. However,more substantial aerosol loadings probably represent less-absorptive aerosols.The opposite covariation pattern occurring over the coastal-adjacent oceans suggests that the polluted oceanic atmosphere is closely correlated with the windward terrestrial aerosols.North central China is strongly affected by dust aerosols that show moderate absorption.This finding may explain the lower variability in the SSA that accompanies increasing aerosol loadings in this region. 相似文献
17.
A coupled meteorology and aerosol/chemistry model WRF-Chem(Weather Research and Forecast model coupled with Chemistry) was used to conduct a pair of simulations with present-day(PD) and preindustrial(PI) emissions over East Asia to examine the aerosol indirect effect on clouds.As a result of an increase in aerosols in January,the cloud droplet number increased by 650 cm-3 over the ocean and East China,400 cm-3 over Central and Southwest China,and less than 200 cm-3 over North China.The cloud liquid water path(LWP) increased by 40-60 g m-2 over the ocean and Southeast China and 30 g m-2 over Central China;the LWP increased less than 5 g m-2 or decreased by 5 g m-2 over North China.The effective radius(Re) decreased by more than 4 μm over Southwest,Central,and Southeast China and 2μm over North China.In July,variations in cloud properties were more uniform;the cloud droplet number increased by approximately 250-400 cm-3,the LWP increased by approximately 30-50 g m-2,and Re decreased by approximately 3 ?m over most regions of China.In response to cloud property changes from PI to PD,shortwave(SW) cloud radiative forcing strengthened by 30 W m-2 over the ocean and 10 W m-2 over Southeast China,and it weakened slightly by approximately 2-10 W m-2 over Central and Southwest China in January.In July,SW cloud radiative forcing strengthened by 15 W m-2 over Southeast and North China and weakened by 10 W m-2 over Central China.The different responses of SW cloud radiative forcing in different regions was related to cloud feedbacks and natural variability. 相似文献
18.
Development of RAMS-CMAQ to Simulate Aerosol Optical Depth and Aerosol Direct Radiative Forcing and Its Application to East Asia 下载免费PDF全文
下载免费PDF全文 HAN Xiao ZHANG Mei-Gen LIU Xiao-Hong Steven GHAN XIN Jin-Yuan WANG Li-Li 《大气和海洋科学快报》2009,2(6):368-375
The air quality modeling system RAMS （Regional Atmospheric Modeling System）-CMAQ （Models-3 Community Multi-scale Air Quality） is developed to simulate the aerosol optical depth （AOD） and aerosol direct forcing （DF）. The aerosol-specific extinction, single scattering albedo, and asymmetry factor are parameterized based on Mie theory taking into account the aerosol size distribution, composition, refractive index, and water uptake of solution particles. A two-stream solar radiative model considers all gaseous molecular absorption, Rayleigh scattering, and aerosols and clouds. RAMSCMAQ is applied to simulate all major aerosol concentrations （e.g., sulfate, nitrate, ammonium, organic carbon, black carbon, fine soil, and sea salt） and AOD and DF over East Asia in 2005. To evaluate its performance, the simulated AOD values were compared with ground-based in situ measurements. The comparison shows that RAMSCMAQ performed well in most of the model domain and generally captured the observed variations. High AOD values （0.2-1.0） mainly appear in the Sichuan Basin as well as in central and southeastern China. The geographic distribution of DF generally follows the AOD distribution patterns, and the DF at the top-of-the-atmosphere is less than -25 and -20 W m^-2 in clear-sky and all-sky over the Sichuan Basin. Both AOD and DF exhibit seasonal variations with lower values in July and higher ones in January. The DF could obviously be impacted by high cloud fractions. 相似文献
19.
利用地面激光雷达、太阳光度计观测反演气溶胶光学特性参数,结合PM2.5观测数据,分析了2018年1月25—28日北京一次完整污染过程中气溶胶光学特性变化。基于观测数据,利用短波辐射传输模式计算了不同程度污染日,晴空背景下气溶胶对辐射加热率的改变程度。结果表明:清洁日（25日）,PM2.5日平均质量浓度为19.00 μg·m-3,440 nm气溶胶光学厚度为0.13,单次散射反照率为0.87,整层气溶胶消光系数低于0.10 km-1,短波辐射均为增温效应;污染期间（26—27日）,PM2.5日平均质量浓度为83.21 μg·m-3,气溶胶光学厚度为2.48,气溶胶散射能力增强,单次散射反照率达到0.94,气溶胶主要消光层厚度提升至3.00 km高度,消光系数平均值为0.43 km-1,气溶胶在垂直方向的变化导致气溶胶中上层（1.50~3.00 km高度）加热作用强烈,短波辐射加热率平均值达到13.89 K·d-1,而低层（1.50 km高度以内）加热作用较弱,加热率平均值仅为0.99 K·d-1。气溶胶散射能力增强导致加热作用减弱,污染日加热率对于气溶胶散射能力变化更敏感。 相似文献
20.
The direct and semi-direct radiative effects of anthropogenic aerosols on the radiative transfer and cloud fields in the Western United States (WUS) according to seasonal aerosol optical depth (AOD) and regional climate are examined using a regional climate model (RCM) in conjunction with the aerosol fields from a GEOS-Chem chemical-transport model (CTM) simulation. The two radiative effects cannot be separated within the experimental design in this study, thus the combined direct- and semi-direct effects are called radiative effects hereafter. The CTM shows that the AOD associated with the anthropogenic aerosols is chiefly due to sulfates with minor contributions from black carbon (BC) and that the AOD of the anthropogenic aerosol varies according to local emissions and the seasonal low-level winds. The RCM-simulated anthropogenic aerosol radiative effects vary according to the characteristics of regional climate, in addition to the AOD. The effects on the top of the atmosphere (TOA) outgoing shortwave radiation (OSRT) range from ?0.2?Wm?2 to ?1?Wm?2. In Northwestern US (NWUS), the maximum and minimum impact of anthropogenic aerosols on OSRT occurs in summer and winter, respectively, following the seasonal AOD. In Arizona-New Mexico (AZNM), the effect of anthropogenic sulfates on OSRT shows a bimodal distribution with winter/summer minima and spring/fall maxima, while the effect of anthropogenic BC shows a single peak in summer. The anthropogenic aerosols affect surface insolation range from ?0.6?Wm?2 to ?2.4?Wm?2, with similar variations found for the effects on OSRT except that the radiative effects of anthropogenic BC over AZNM show a bimodal distribution with spring/fall maxima and summer/winter minima. The radiative effects of anthropogenic sulfates on TOA outgoing longwave radiation (OLR) and the surface downward longwave radiation (DLRS) are notable only in summer and are characterized by strong geographical contrasts; the summer OLR in NWUS (AZNM) is reduced (enhanced) by 0.52?Wm?2 (1.14?Wm?2). The anthropogenic sulfates enhance (reduce) summer DLRS by 0.2?Wm?2 (0.65?Wm?2) in NWUS (AZNM). The anthropogenic BC affect DLRS noticeably only in AZNM during summer. The anthropogenic aerosols affect the cloud water path (CWP) and the radiative transfer noticeably only in summer when convective clouds are dominant. Primarily shortwave-reflecting anthropogenic sulfates decrease and increase CWP in AZNM and NWUS, respectively, however, the shortwave-absorbing anthropogenic BC reduces CWP in both regions. Due to strong feedback via convective clouds, the radiative effects of anthropogenic aerosols on the summer radiation field are more closely correlated with the changes in CWP than the AOD. The radiative effect of the total anthropogenic aerosols is dominated by the anthropogenic sulfates that contribute more than 80% of the total AOD associated with the anthropogenic aerosols. 相似文献