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1.
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
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.
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. 相似文献
4.
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
5.
Xiaoyan WU Jinyuan XIN Wenyu ZHANG Chongshui GONG Yining MA Yongjing MA Tianxue WEN Zirui LIU Shili TIAN Yuesi WANG Fangkun WU 《大气科学进展》2020,37(12):1310-1322
Industrial pollution has a significant effect on aerosol properties in Changsha City, a typical city of central China. Therefore, year-round measurements of aerosol optical, radiative and chemical properties from 2012 to 2014 at an urban site in Changsha were analyzed. During the observation period, the energy structure was continuously optimized, which was characterized by the reduction of coal combustion. The aerosol properties have obvious seasonal variations. The seasonal average aerosol optical depth (AOD) at 500 nm ranged from 0.49 to 1.00, single scattering albedo (SSA) ranged from 0.93 to 0.97, and aerosol radiative forcing at the top of the atmosphere (TOA) ranged from ?24.0 to 3.8 W m?2. The chemical components also showed seasonal variations. Meanwhile, the scattering aerosol, such as organic carbon, SO42?, NO3?, and NH4+ showed a decrease, and elemental carbon increased. Compared with observation in winter 2012, AOD and TOA decreased by 0.14 and ?1.49 W m?2 in winter 2014. The scattering components, SO42?, NO3? and NH4+, decreased by 12.8 μg m?3 (56.8%), 9.2 μg m?3 (48.8%) and 6.4 μg m?3 (45.2%), respectively. The atmospheric visibility and pollution diffusion conditions improved. The extinction and radiative forcing of aerosol were significantly controlled by the scattering aerosol. The results indicate that Changsha is an industrial city with strong scattering aerosol. The energy structure optimization had a marked effect on controlling pollution, especially in winter (strong scattering aerosol). 相似文献
6.
利用MODIS卫星资料对中国中东部和印度次大陆气溶胶特性的分析 总被引：1，自引：1，他引：0
利用Terra和Aqua卫星上的MODIS探测反演气溶胶产品,比较分析了中国中东部和印度次大陆地区的气溶胶物理特性的异同。研究结果表明:中国中东部气溶胶类型以烟尘为主,印度次大陆地区东、西部分别以烟尘和沙尘为主。两地气溶胶光学厚度均有明显的年际变化,冬季低,夏季高。在夏季,两地烟尘所占比例都很大,且光学厚度也大,故两地污染状况都比较严重。总体来说,中国中东部地区污染程度要高于印度次大陆地区。 相似文献
7.
东亚夏季风环流对气溶胶分布的影响 总被引：2，自引：1，他引：1
用2001—2012年逐月的MODIS-TERRA卫星观测气溶胶光学厚度(AOD)资料和NCEP/NCAR风场资料,分析了5—8月东亚地区AOD的时-空分布特征,研究东亚夏季风环流对气溶胶时-空分布的影响。主要结论如下:5—8月的中国东部及邻近海洋上AOD有着显著的季节演变特征,尤其是32.5 °N附近的AOD高值区,其强度和范围在5—8月逐渐增强然后又减弱。东亚夏季风通过环流输送作用对各地的AOD产生了不同程度的影响,使中国南部AOD减少,而华北和东北地区AOD增加。在强、弱季风年背景下,7月观测的AOD差异与环流输送作用差异的分布特征有着一定的相似性,体现出东亚夏季风年际变化对气溶胶分布的影响。在东亚夏季风演变的不同阶段,季风环流对气溶胶输送大部分情况下,可解释局地气溶胶变化10%~20%的方差。 相似文献
8.
A Modeling Study of the Effects of Direct Radiative Forcing
Due to Carbonaceous Aerosol on the Climate in East Asia 总被引：6，自引：0，他引：6
The study investigated the effects of global direct radiative forcing due to carbonaceous
aerosol on the climate in East Asia, using the CAM3 developed by NCAR. The results showed that
carbonaceous aerosols cause negative forcing at the top of the atmosphere (TOA) and surface under
clear sky conditions, but positive forcing at the TOA and weak negative forcing at the surface under
all sky conditions. Hence, clouds could change the sign of the direct radiative forcing at the TOA,
and weaken the forcing at the surface. Carbonaceous aerosols have distinct effects on the summer
climate in East Asia. In southern China and India, it caused the surface temperature to increase,
but the total cloud cover and precipitation to decrease. However, the opposite effects are caused
for most of northern China and Bangladesh. Given the changes in temperature, vertical velocity,
and surface streamflow caused by carbonaceous aerosol in this simulation, carbonaceous aerosol
could also induce summer precipitation to decrease in southern China but increase in northern China. 相似文献
9.
Seasonal variation features of aerosol optical depth (AOD) over East China and India in association with the Asian monsoon system are investigated, based on the latest AOD data derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Terra satellite, the NCEP Final (FNL) Operational Global Analysis data, the Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP) data, and the NCEP/NCAR reanalysis data from March 2000 to February 2017. The results indicate that AOD in East China is significantly larger than that in India, especially in spring. The seasonal mean AOD in East China is high in both spring and summer but low in fall and winter. However, the AOD averaged over India is highest in summer and lower in spring, fall, and winter. Analysis reveals that AOD is more closely related to changes in surface wind speed in East China, while no obvious relation is found between precipitation and the AOD distribution on the seasonal timescale. As aerosols are mainly distributed in the atmospheric boundary layer (ABL), the stability of the ABL represented by Richardson number (Ri) is closely correlated with spatial distribution of AOD. The upper and lower tropospheric circulation patterns significantly differ between East China and India, resulting in different effects on the AOD. The effect of advection associated with lower tropospheric circulation on the AOD and the influence of convergence and divergence on the AOD distribution play different roles in maintaining the AOD in East China and India. These results improve our understanding of the mechanism responsible for and differences among the aerosol changes in East China and India. 相似文献
10.
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
11.
利用2000年3月—2017年3月Terra卫星反演的MODIS气溶胶光学厚度(Aerosol Optical Depth,AOD)资料、NCEP的fnl全球业务分析数据、CMAP降水资料、CERES SYN1deg Ed 4月平均资料以及NCEP/NCAR再分析资料等,依据中国东部冬季区域平均AOD距平具有显著的年际变化特征,将历年冬季AOD划分为5个不同的污染等级,并探讨了不同污染等级的局地成因及其与冬季风环流的联系。结果表明,中国东部冬季AOD区域平均值与气候要素场有很好的相关关系,即AOD异常偏高(低)时,入射到地面的太阳短波辐射通量减小(增加),地面气温降低(增加),地气系统冷却(加热),地面降水呈现华北与江淮内陆少、江淮东南多(华北与江淮西南部多、江淮地区东部少)的分布特征。中国东部AOD值异常偏高与风速异常偏小有关,且这种负相关关系在华北表现最明显:即AOD异常偏高(低)时,华北地面风速偏小(大),江淮地面风速偏大(小)。个例分析表明,纬向风速异常偏小、东风异常及阿留申低压偏弱是2013年AOD异常偏高的主要原因。 相似文献
12.
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
13.
利用MODIS光学厚度遥感产品研究北京及周边地区的大气污染 总被引：53，自引：2，他引：53
对2001年在北京地区利用太阳光度计观测的气溶胶光学厚度和NASA发布的MODIS气溶胶产品进行了比较,验证了这一卫星遥感产品的可靠性;比较了2001年MODIS气溶胶光学厚度(AOD)产品和由空气污染指数(API)计算的每日平均可吸入颗粒物(PM10)浓度,得到了比较高的相关系数,证实该气溶胶产品可用于污染分析.将北京地区AOD与气象能见度观测资料进行比较,得到了不同季节的气溶胶"标高".利用统计的不同季节的气溶胶标高,从光学厚度的季节分布得到了能见度(能见距离)的季节分布.气溶胶光学厚度图像的个例分析表明,除局地排放外,周边区域(主要为西南和南向)的输送对北京市区的空气污染贡献份额较大.卫星遥感气溶胶可以比较直观地再现污染物的区域分布和输送,不仅为研究全球气候变化也为研究区域环境的空气质量提供了一种有效手段. 相似文献
14.
Identification of Aerosol Types and Their Optical Properties in the North China Plain Based on Long-Term AERONET Data 
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下载免费PDF全文 SUN Li XIA Xiang-Ao WANG Pu-Cai CHEN Hong-Bin Philippe GOLOUB ZHANG Wen-Xing 《大气和海洋科学快报》2013,(4):216-222
Characterization of aerosols is required to reduce uncertainties in satellite retrievals of global aerosols and for modeling the effects of these aerosols on climate.Aerosols in the North China Plain(NCP) are complex,which provides a good opportunity to study key aerosol optical properties for various aerosol types.A cluster analysis of key optical properties obtained from Aerosol Robotic Network(AERONET) data in Beijing and Xianghe during 2001-11 was performed to identify dominant aerosol types and their associated optical properties.Five dominant aerosol types were identified.The results show that the urban/industrial aerosol of moderate absorption was dominant in the region and that this type varied little with season.Urban/industrial aerosol of weak absorption was the next most common type and mainly occurs in summer,followed by that strong aerosols occurring mainly in winter.All were predominantly fine mode particles.Mineral dust(MD) and polluted dust(PD) occurred mainly in spring,followed by winter,and their absorption decreased with wavelength.In addition,aerosol dynamics and optical parameters such as refractive index and asymmetry factor were examined.Results show that the size of coarse mode particles decreased with AOD indicating the domination of external mixing between aerosols. 相似文献
15.
Snow/Rainfall Anomaly in Winter of Northern China and Associated Atmospheric Circulation and Aerosol Distribution Features 下载免费PDF全文
下载免费PDF全文 Based on the NCEP/NCAR reanalysis data,China station precipitation data from 1960 to 2008,and aerosol optical depth (AOD) data in northern China from 1980 to 2004,this paper investigates the variability of winter snow/rainfall in northern China and the associated atmospheric circulation and aerosol distribution characteristics by using composite analysis.The results show that winter precipitation in northern China has been generally increasing since the 1960s.Among the winters of 1990-2008,the years with more rain/snow (MRSYs) are 1998,2003,and 2006,while the years with less rain/snow (LRSYs) are 2005,1997,and 2001.Composite analysis finds that the main differences of atmospheric circulation in East Asia between MRSYs and LRSYs are as follows.1) In MRSYs,strong low-level cold air over the northern polar region and Taymyr Peninsula migrates southward to northern China (Northwest,North,and Northeast China),establishing a channel favoring continuous southward transport of cold air.In LRSYs,however,this cold air channel does not exist.2) In MRSYs,the frontal zone and westerlies are over North China,and the low-level geopotential height field from eastern China to West Pacific exhibits an "east high,west low" pattern,which is conducive to easterly and southerly airflows moving northward along 110 E.In LRSYs,the 500-hPa prevailing westerly winds stay far away from China and the low-level southeasterlies move to higher latitudes,which are disadvantageous to the development of precipitation in northern China.3) In MRSYs,large-scale upward motions combined with local-scale updrafts develop into strong slanted climbing airflows,forming a vertical circulation that favors the generation of heavy snows in eastern China.In LRSYs,the vertical circulation moves eastward into the Pacific Ocean.Furthermore,the correlation analysis on AOD and winter precipitation during the period 1980-2004 in northern China reveals that AOD differs significantly between MRSYs and LRSYs and the annual variation of winter rain/snow is positively correlated to the annual variation of AOD with a correlation coefficient of 0.415 at the 0.001 significance level. 相似文献
16.
华东区域夏季行星边界层大气稳定度的气候特征及其与气溶胶的联系 总被引：2，自引：1，他引：1
利用1979-2008年夏季（6—8月）逐日NCEP／NACR再分析资料、MODIS卫星的气溶胶资料等,研究了华东区域夏季行星边界层大气稳定度的气候特征与年际变化,分析了大气稳定度和相应的加热场与气溶胶光学厚度（aerosol optical depth,AOD）的联系。结果表明：华东区域夏季行星边界层大气稳定度在空间上分布不均匀,时间上具有明显的年际变化。边界层中的非绝热加热率、大气稳定度及气溶胶光学厚度三者之间可能存在密切联系。利用经验正交函数分析了华东区域总体理查森数Rib的距平场,得到了边界层稳定度分布的3个主要模态,这3个模态所代表的边界层大气稳定度异常与夏季风环流异常密切相关,特别是P-J型遥相关波列和西太平洋副热带高压在中国东部大气边界层稳定度变化中可能起着非常重要的作用。 相似文献
17.
Boru MAI Xuejiao DENG Zhanqing LI Jianjun LIU Xiang'ao XIA Huizheng CHE Xia LIU Fei LI Yu ZOU Maureen CRIBB 《大气科学进展》2018,35(2):195-208
Aerosol optical properties and direct radiative effects on surface irradiance were examined using seven years(2006–2012)of Cimel sunphotometer data collected at Panyu—the main atmospheric composition monitoring station in the Pearl River Delta(PRD) region of China. During the dry season(October to February), mean values of the aerosol optical depth(AOD)at 550 nm, the ?ngstr?m exponent, and the single scattering albedo at 440 nm(SSA) were 0.54, 1.33 and 0.87, respectively.About 90% of aerosols were dominated by fine-mode strongly absorbing particles. The size distribution was bimodal, with fine-mode particles dominating. The fine mode showed a peak at a radius of 0.12 μm in February and October(~0.10μm~3μm~(-2)). The mean diurnal shortwave direct radiative forcing at the surface, inside the atmosphere(FATM), and at the top of the atmosphere, was-33.4 ± 7.0, 26.1 ± 5.6 and-7.3 ± 2.7 W m~(-2), respectively. The corresponding mean values of aerosol direct shortwave radiative forcing per AOD were-60.0 ± 7.8, 47.3 ± 8.3 and-12.8 ± 3.1 W m~(-2), respectively. Moreover,during the study period, FATMshowed a significant decreasing trend(p 0.01) and SSA increased from 0.87 in 2006 to 0.91 in 2012, suggesting a decreasing trend of absorbing particles being released into the atmosphere. Optical properties and radiative impacts of the absorbing particles can be used to improve the accuracy of inversion algorithms for satellite-based aerosol retrievals in the PRD region and to better constrain the climate effect of aerosols in climate models. 相似文献
18.
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
19.
气溶胶已是东亚地区最主要的大气污染物之一,其时空分布会受到东亚季风气候的影响。利用2000～2014年MODIS/AOD（Moderate-resolution Imaging Spectroradiometer/Aerosol Optical Depth）和NCEP月平均气象场再分析资料,本研究分析了东亚冬季风长期变化趋势、气溶胶年际变化规律,探讨了东亚冬季风强度变化对气溶胶分布的影响。基于MODIS/AOD,发现近10年东亚地区冬季AOD呈现上升趋势,最大值为2007年的0.44,高值区覆盖四川盆地、华北平原及长江中下游大部分地区。风场特征类冬季风指数分析表明,东亚冬季风存在明显的年际和年代际差异,近年出现逐渐减弱的趋势。强冬季风年,海陆气压差增大、东亚大槽加深增强,东亚地区偏北风异常,风场的增强将引导更多冷空气南下,从而给东亚大部分地区带来明显的降温天气;弱年相反。气象场差异引起气溶胶分布变化,强年较强的偏北风将气溶胶向南方输送,东亚地区AOD出现“北低南高”的空间分布;弱年偏北风较弱,导致气溶胶集中在华北平原一带,AOD出现“北高南低”的空间分布。 相似文献
20.
Current global climate models cannot resolve the complex topography over the Tibetan Plateau (TP) due to their coarse resolution. This study investigates the impacts of horizontal resolution on simulating aerosol and its direct radiative effect (DRE) over the TP by applying two horizontal resolutions of about 100 km and 25 km to the Chinese Academy of Sciences Flexible Global Ocean-Atmosphere Land System (CAS FGOALS-f3) over a 10-year period. Compared to the AErosol RObotic NETwork observations, a high-resolution model (HRM) can better reproduce the spatial distribution and seasonal cycles of aerosol optical depth (AOD) compared to a low-resolution model (LRM). The HRM bias and RMSE of AOD decreased by 0.08 and 0.12, and the correlation coefficient increased by 0.22 compared to the LRM. An LRM is not sufficient to reproduce the aerosol variations associated with fine-scale topographic forcing, such as in the eastern marginal region of the TP. The difference between hydrophilic aerosols in an HRM and LRM is caused by the divergence of the simulated relative humidity (RH). More reasonable distributions and variations of RH are conducive to simulating hydrophilic aerosols. An increase of the 10-m wind speed in winter by an HRM leads to increased dust emissions. The simulated aerosol DREs at the top of the atmosphere (TOA) and at the surface by the HRM are –0.76 W m–2 and –8.72 W m–2 over the TP, respectively. Both resolution models can capture the key feature that dust TOA DRE transitions from positive in spring to negative in the other seasons. 相似文献