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1.
In this study, we systematically document the link between dust episodes and local scale regional aerosol optical properties over Jaipur located in the vicinity of Thar Desert in the northwestern state of Rajasthan. The seasonal variation of AOT500 nm (aerosol optical thickness) shows high values (0.51?±?0.18) during pre-monsoon (dust dominant) season while low values (0.36?±?0.14) are exhibited during winter. The Ångström wavelength exponent has been found to exhibit low value (<0.25) indicating relative dominance of coarse-mode particles during pre-monsoon season. The AOT increased from 0.36 (Aprilmean) to 0.575 (May–Junemean). Consequently, volume concentration range increases from April through May–June followed by a sharp decline in July during the first active phase of the monsoon. Significantly high dust storms were observed over Jaipur as indicated by high values of single scattering albedo (SSA440 nm?=?0.89, SSA675 nm?=?0.95, SSA870 nm?=?0.97, SSA1,020 nm?=?0.976) than the previously reported values over IGP region sites. The larger SSA values (more scattering aerosol), especially at longer wavelengths, is due to the abundant dust loading, and is attributed to the measurement site’s proximity to the Thar Desert. The mean and standard deviation in SSA and asymmetry parameter during pre-monsoon season over Jaipur is 0.938?±?0.023 and 0.712?±?0.017 at 675 nm wavelength, respectively. Back-trajectory air mass simulations suggest Thar Desert in northwestern India as the primary source of high aerosols dust loading over Jaipur region as well as contribution by long-range transport from the Arabian Peninsula and Middle East gulf regions, during pre-monsoon season.  相似文献   

2.
Satellite-retrieved data on aerosol optical depth (AOD) and Ångström exponent (AE) using a moderate resolution imaging spectrometer (MODIS) were used to analyze large-scale distributions of atmospheric aerosols in East Asia. AOD was relatively high in March (0.44?±?0.25) and low in September (0.24?±?0.21) in the East Asian region in 2009. Sandstorms originating from the deserts and dry areas in northern China and Mongolia were transported on a massive scale during the springtime, thus contributing to the high AOD in East Asia. However, whereas PM10 with diameters ≤10 μm was the highest in February at Anmyon, Cheongwon, and Ulleung, located leeward about halfway through the Korean Peninsula, AOD rose to its highest in May. The growth of hygroscopic aerosols attendant on increases in relative humidity prior to the Asian monsoon season contributed to a high AOD level in May. AE typically appears at high levels (1.30?±?0.37) in August due to anthropogenic aerosols originating from the industrial areas in eastern China, while AOD stays low in summer due to the removal process caused by rainfall. The linear correlation coefficients of the MODIS AOD and ground-based mass concentrations of PM10 at Anmyon, Cheongwon, and Ulleung were measured at 0.4~0.6. Four cases (6 days) of mineral dustfall from sandstorms and six cases (12 days) of anthropogenically polluted particles were observed in the central area of the Korean Peninsula in 2009. PM10 mass concentrations increased at both Anmyon and Cheongwon in the cases of mineral dustfall and anthropogenically polluted particles. Cases of dustfall from sandstorms and anthropogenic polluted particles, with increasing PM10 mass concentrations, showed higher AOD values in the Yellow Sea region.  相似文献   

3.
In order to investigate the characteristic of optical properties of Asian dust particles, the atmospheric aerosol vertical profile was measured with the multi-wavelength LIDAR system, at the Gosan super site (33 degrees 17'N, 126 degrees 10'E) in Jeju Island, Korea, during the ACE-Asia intensive observation period, 11 March-4 May 2001. An air mass backward trajectory analysis, using Hysplit-4, was carried out to track the aerosol plume, with high mass loading, from the Chinese desert regions during the period of Asian dust storm events. Vertical atmospheric aerosol profiles on three major Asian dust storm event days, 22 March and 13 and 26 April 2001, have been analyzed. The LIDAR-derived aerosol optical depth values were compared with those measured by a collocated sunphotometer.  相似文献   

4.
The column-integrated optical and radiative properties of aerosols in the downwind area of East Asia were investigated based on sun/sky radiometer measurements performed from February 2004 to June 2005 at Gwangju (35.23° N, 126.84° E) and Anmyeon (36.54° N, 126.33° E), Korea. The observed aerosol data were analyzed for differences among three seasons: spring (March-May), summer (June-August), and autumn/winter (September-February). The data were also categorized into five types depending on the air mass origin in arriving in the measurement sites: (a) from a northerly direction in spring (S(N)), (b) from a westerly direction in spring (S(W)), (c) cases with a low ?ngstr?m exponent (<0.8) in spring (dust), (d) from a northerly direction in autumn/winter (AW(N)), and (e) from a westerly direction during other seasons (AW(W)). The highest ?ngstr?m exponents (α) at Gwangju and Anmyeon were 1.43?±?0.30 and 1.49?±?0.20, respectively, observed in summer. The lowest column-mean single-scattering albedo (ω) at 440 nm observed at Gwangju and Anmyeon were 0.89?±?0.02 and 0.88?±?0.02, respectively, during a period marked by the advection of dust from the Asian continent. The highest ω values at Gwangju and Anmyeon were 0.95?±?0.02 and 0.96?±?0.02, respectively, observed in summer. Variations in the aerosol radiative-forcing efficiency (β) were related to the conditions of the air mass origin. The forcing efficiency in summer was -131.7 and -125.6 W?m(-2) at the surface in Gwangju and Anmyeon, respectively. These values are lower than those under the atmospheric conditions of spring and autumn/winter. The highest forcing efficiencies in autumn/winter were -214.3 and -255.9 W?m(-2) at the surface in Gwangju and Anmyeon, respectively, when the air mass was transported from westerly directions.  相似文献   

5.
Episodes of large-scale transport of airborne dust and anthropogenic pollutant particles from different sources in the East Asian continent in 2008 were identified by National Oceanic and Atmospheric Administration satellite RGB (red, green, and blue)-composite images and the mass concentrations of ground level particulate matter. These particles were divided into dust, sea salt, smoke plume, and sulfate by an aerosol classification algorithm. To analyze the aerosol size distribution during large-scale transport of atmospheric aerosols, aerosol optical depth (AOD) and fine aerosol weighting (FW) of moderate imaging spectroradiometer aerosol products were used over the East Asian region. Six episodes of massive airborne dust particles, originating from sandstorms in northern China, Mongolia, and the Loess Plateau of China, were observed at Cheongwon. Classified dust aerosol types were distributed on a large-scale over the Yellow Sea region. The average PM10 and PM2.5 ratio to the total mass concentration TSP were 70% and 15%, respectively. However, the mass concentration of PM2.5 among TSP increased to as high as 23% in an episode where dust traveled in by way of an industrial area in eastern China. In the other five episodes of anthropogenic pollutant particles that flowed into the Korean Peninsula from eastern China, the anthropogenic pollutant particles were largely detected in the form of smoke over the Yellow Sea region. The average PM10 and PM2.5 ratios to TSP were 82% and 65%, respectively. The ratio of PM2.5 mass concentrations among TSP varied significantly depending on the origin and pathway of the airborne dust particles. The average AOD for the large-scale transport of anthropogenic pollutant particles in the East Asian region was measured to be 0.42 ± 0.17, which is higher in terms of the rate against atmospheric aerosols as compared with the AOD (0.36 ± 0.13) for airborne dust particles with sandstorms. In particular, the region ranging from eastern China, the Yellow Sea, and the Korean Peninsula to the Korea East Sea was characterized by high AOD distributions. In the episode of anthropogenic polluted aerosols, FW averaged 0.63 ± 0.16, a value higher than that in the episode of airborne dust particles (0.52 ± 0.13) with sandstorms, showing that fine anthropogenic pollutant particles contribute greatly to atmospheric aerosols in East Asia.  相似文献   

6.
Soil dust particles transported from loess regions of the Asian continent, called Asian dust, highly influences the air quality of north-eastern Asia and the northern Pacific Ocean. In order to investigate the effects of these dust storms on the chemical composition of atmospheric aerosol particles with different size, measurements of size distributions of total aerosol and major ion species were carried out on Jeju Island, Korea during April 2001. Juju Island was chosen for the study because the levels of emissions of anthropogenic air pollutants are very low. A 5-stage cascade impactor was used to sample size-fractionated aerosol particles. Samples were analyzed for major water-soluble ions using Dionex DX-120 ion chromatograph. The average mass concentration of total aerosol was found to be 24.4 and 108.3 microg m(-3) for non-Asian dust and Asian dust periods, respectively. The total aerosol size distribution, measured during the non-Asian dust period, was bimodal, whereas the coarse particles dominated the size distribution of total aerosol during the Asian dust period. It was found that SO4(2-), NH4+ and K+ were mainly distributed in fine particles, while Cl-, NO3-, Na+, Mg2+ and Ca2+ were in coarse particles. Although SO4(2-) was mainly distributed in fine particles, during the Asian dust period, the concentrations in coarse particles were significantly increased. This indicates heterogeneous oxidation of SO2 on wet surfaces of basic soil dust particles. The NH4+ was found to exist as (NH4)2SO4 in fine particles, with a molar ratio of NH4+ to SO4(2-) of 2.37 and 1.52 for non-Asian dust and Asian dust periods, respectively. Taking into account the proximity of the sampling site to the sea, and the observed chloride depletion, coarse mode nitrate, during the non-Asian dust period, is assumed to originate from the reaction of nitric acid with sodium chloride on the surfaces of sea-salt particles although the chloride depletion was not shown to be large enough to prove this assumption. During the Asian dust period, however, chloride depletion was much smaller, indicating coarse nitrate particles were mainly produced by the reaction of nitric acid with surfaces of basic soil particles. Most chloride and sodium components were shown to originate from sea-salt particles. Asian dust aerosols, arriving at Jeju Island, contained considerable amounts of sea-salt particles as they passed over the Yellow Sea. Ca2+ was shown to be the most abundant species in Asian dust particles.  相似文献   

7.
Atmospheric surface aerosol radiative forcing (SARF) ΔF, forcing efficiency ΔFe and fractional forcing efficiency ΔFFe evaluated from cloud-screened narrowband spectral and thermal-offset-corrected radiometric observations during the Asia dust outbreak episodes in Gwangju, Republic of Korea are reported in this study. Columnar aerosol optical properties (aerosol optical depth (AOD), τ , Angstrom exponent α, mass concentration of fine and coarse mode particles) were also reported for the station between January 2000 and May 2001 consisting of 211cloud-free days. Results indicate that majority of the AOD were within the range 0.25–0.45 while some high aerosol events in which AODs ≥ 0.6 were observed during the severe dust episodes. For example, AOD increases from annual average value of 0.34 ± 0.13 at 501 nm to values >0.60 during the major dust events of March 27–30 and April 7–9, 2000, respectively. The α 501–870 nm which is often used as a qualitative indicator of aerosol particle size had values ranging from 0.01 to 1.77. The diurnal forcing efficiency ΔDFe at Gwangju was estimated to be −81.10 ± 5.14 W m −2/τ 501 nm and −47.09 ± 2.20 W m −2/τ 501 nm for the total solar broadband and visible band pass, respectively while the fractional diurnal forcing efficiency ΔFDFe were −15.8 ± 0.64%/τ 501 nm and −22.87 ± 1.13%/τ 501 nm for the same band passes. Analyses of the 5-day air-mass back trajectories were further developed for Gwangju in order to classify the air-mass and types of aerosol reaching the site during the Asia dust episodes.  相似文献   

8.
Atmospheric aerosols are an important contributing factor to turbidity in urban areas besides having impact on health. Aerosol characteristics show a high degree of variability in space and time as anthropogenic share of total aerosol loading is quite substantial and is essential to monitor the aerosol features over long time scales. In the present study extensive observations of columnar aerosol optical depth (AOD), total columnar ozone (TCO) and precipitable water content (PWC) have been carried over a tropical urban city of Hyderabad, India. Significant variations of AOD have been observed during course of the day with low values of AOD during morning and evening hours and high values during afternoon hours. Spectral variation of AOD exhibits high AOD at smaller wavelengths and vice versa except a slight enhancement in AOD at 500 nm. Anomalies in AOD, particulate matter and black carbon concentrations have been observed during May, 2003. Back trajectory analysis of air mass during these episodes suggested variation in air mass trajectories. Analysis of the results suggests that air trajectories from land region north of study area cause high loading of atmospheric aerosols. The results are discussed in the paper.  相似文献   

9.
利用全自动太阳辐射计,对深圳世界大运会主场馆附近大气特性开展了连续观测(2011-08-11-2011-09-03)。获得了大运会期间(12 d)和大运会后(11 d),气溶胶光学厚度(AOD)等参数的变化情况,并对气溶胶光学和微物理特性进行了分析。结果表明,大运会期间440 nm处的AOD平均值为0.273,大运会之后的AOD平均值为0.983,大运会期间较大运会之后AOD平均值有显著降低。粒子谱分布等气溶胶微物理特性参数的分析还表明, AOD降低主要是由于细粒子含量的减少,说明环境控制措施对于空气质量产生了较好的改进效果。  相似文献   

10.
将MODIS数据反演得出的气溶胶光学厚度与无锡市区实测得到的PM2.5质量浓度进行相关性分析,结果两者的直接相关性较低,相关系数为0.283 4。气溶胶光学厚度经垂直分布和湿度修正后,两者相关性显著提高,相关系数为0.565 9。虽然修正过程存在误差,相关性未达预期程度,但该方法得到的气溶胶光学厚度可作为PM2.5监测的有效补充。  相似文献   

11.
碳酸盐碳测定在沙尘暴来源地识别中的应用   总被引:7,自引:0,他引:7  
根据中国大气颗粒物特点 ,在国内沙尘暴研究中首次尝试利用碳酸盐碳进行沙尘暴来源地识别。测定了一系列黄沙、大气颗粒物和沙尘暴源区土壤样品。初步了解了上述样品中碳酸盐碳含量情况 ,结合国外研究结果对影响北京的沙尘暴源区进行推测并与其他方法作了比较  相似文献   

12.
利用2000—2019年TERRA和AQUA相结合的气溶胶光学厚度(AOD)产品数据,从时间和空间角度分析了常州市AOD的变化特征。结果显示:(1)2012—2019年常州市PM2.5与AOD年均值的相关系数为0.898,表明AOD产品适用于常州市气溶胶污染年际变化研究。(2)2000—2019年常州市AOD年均值范围为0.463~0.688,平均值为0.627。其中,2000—2007年常州市AOD年均值整体呈上升趋势,2011—2019年呈下降趋势。常州市AOD的月变化趋势呈倒“U”形,特征最高值出现在6月,最低值出现在12月。常州市AOD有明显的季节变化特征,夏季最高,冬季最低。(3)常州市AOD高值主要分布在西部的溧阳市金坛区,北部的新北区也存在少量高值分布。(4)通过Moran指数发现,常州市Moran指数均大于零,表明各年份AOD均呈集聚状态。2000—2010年常州市AOD的空间集聚程度较高,2010年以后的空间集聚效应逐渐减弱。空间热点分析表明,2011—2019年常州市AOD高值集聚区域相比2000—2010年有所减少,冷点集聚区域有所增加,AO...  相似文献   

13.
Measurements of aerosols were made in 2001 and 2002 at Dunhuang (40 degrees 00'N, 94 degrees 30'E), China to understand the nature of atmospheric particles over the desert areas in the Asian continent. Balloon-borne measurements with an optical particle counter suggested that particle size and concentration had noticeable peaks in super micron size range not only in the boundary mixing layer but also in the free troposphere. Super-micron particle concentration largely decreased in the mid tropopause (from 5 to 10 km; above sea level, a.s.l.). Lidar measurements made during August 2002 at Dunhuang suggested the possibility that mixing of dust particles occurred from near the ground to about 6 km even under calm weather conditions, and a large depolarization ratio of particulate matter was found in the aerosol layer. The top of the aerosol layer was found at heights of nearly 6 km (a.s.l.). It is strongly suggested that nonspherical dust particles (Kosa particles) frequently diffused in the free atmosphere over the Taklamakan desert through small-scale turbulences and are possible sources of dust particles of weak Kosa events that have been identified in the free troposphere not only in spring but also in summer over Japanese archipelago. Electron microscopic experiments of the particles collected in the free troposphere confirmed that coarse and nonspherical particles observed by the mineral particle were major components of coarse mode (diameter larger than 1 microm) below about 5 km over Dunhuang, China.  相似文献   

14.
Lidar measurements of temperature for the upper troposphere and lower stratosphere are commonly derived by the Raman technique. Lidar signals derived from vibrational Raman processes have been subjected to numerous simulation tests to examine their sensitivity to the presence of aerosols and ozone in the atmosphere. The influence of aerosols characteristics (wavelength dependence of aerosol extinction and particle phase function) and of ozone concentration on Raman temperature profiles is estimated. Simulations indicate large temperature deviations for post-volcanic conditions. For a Raman backscatter at 607 nm, bias is below 1 K for a total optical depth less than 9 x 10(-3) in the case of a stratospheric contamination and less than 6 x 10(-3) for a tropospheric contamination. The effect of aerosols depends on phase function and a few parameters such as altitude, optical depth and the shape of the high-altitude cloud. The wavelength dependence of aerosol extinction has some influence only for severe post-volcanic conditions (Scattering Ratio, SR >2). For a Raman backscatter at 387 nm, bias is larger and can be significant even in background aerosol conditions. Changes in the ozone density profile lead to significant Raman temperature deviations only for some specific conditions. Results suggest that both aerosol and ozone corrections are necessary to obtain an accuracy better than the 1 K requested for most atmospheric applications.  相似文献   

15.
This study explored the use of satellite data to monitor carbon monoxide (CO) and particulate matter (PM) in Northern Thailand during the dry season when forest fires are known to be an important cause of air pollution. Satellite data, including Measurement of Pollution in the Troposphere (MOPITT) CO, Moderate Resolution Imaging Spectroradiometer aerosol optical depth (MODIS AOD), and MODIS fire hotspots, were analyzed with air pollution data measured at nine automatic air quality monitoring stations in the study area for February–April months of 2008–2010. The correlation analysis showed that daily CO and PM with size below 10 μm (PM10) were associated with the forest fire hotspot counts, especially in the rural areas with the maximum correlation coefficient (R) of 0.59 for CO and 0.65 for PM10. The correlations between MODIS AOD and PM10, between MOPITT CO and CO, and between MODIS AOD and MOPITT CO were also analyzed, confirming the association between these variables. Two forest fire episodes were selected, and the dispersion of pollution plumes was studied using the MOPITT CO total column and MODIS AOD data, together with the surface wind vectors. The results showed consistency between the plume dispersion, locations of dense hotspots, ground monitoring data, and prevalent winds. The satellite data were shown to be useful in monitoring the regional transport of forest fire plumes.  相似文献   

16.
选用2001年1月-2015年12月MODIS数据,运用线性趋势等方法研究华东地区气溶胶光学厚度(AOD)的变化特征及影响因素。结果表明,2001-2015年华东地区AOD平均值变化范围在0.4~0.7之间,且呈现递减趋势。山东省西部、安徽省北部及江苏省AOD相对较高;福建省、浙江省南部及江西省南部地区AOD较低。华东地区气溶胶最低值出现在12月,最高值出现在6月;虽然冬季AOD变化趋势增长较高,但最高值仍出现在夏季。AOD主要受地形、NDVI、风速及人类活动等因素的影响,地形、NDVI、风速均与AOD呈负相关。  相似文献   

17.
利用长三角地区浦东、东滩、太湖3个测站的太阳光度计CE318地基遥感观测得到的气溶胶光学厚度(AOD)数据对风云三号气象卫星FY-3A/B MERSI反演的550 nm波长AOD进行有效性验证。结果表明,FY-3A的反演结果相关系数高于0.96,仅有20%的样本表现出较大的偏差。FY-3B的相关系数最高为0.77,均方根误差(RMSE)最大为0.35。太湖站点的相关系数比浦东大,说明MERSI的反演算法在太湖更适用。FY-3A/B MERSI反演结果总体上偏小,存在一定的系统偏差,主要由气溶胶模型的假设、设备标定、选择像素比例等原因造成。  相似文献   

18.
Land use affects the global climate through greenhouse gas and aerosol emissions, as well as through changes in biophysical properties of the surface. Anthropogenic land use change over time has caused substantial climate forcing related to albedo, i.e. the share of solar radiation reflected back off the ground. There is growing concern that albedo change may offset climate benefits provided by afforestation, bioenergy or other emission reduction measures that affect land cover. Conversely, land could be managed actively to increase albedo as a strategy to combat global warming.Albedo change can be directly linked to radiative forcing, which allows its climate impact to be compared with that of greenhouse gases in Life Cycle Assessment (LCA). However, the most common LCA methods are static and linear and thus fail to account for the spatial and temporal dependence of albedo change and its strength as a climate forcer. This study sought to develop analytical methods that better estimate radiative forcing from albedo change by accounting for spatial and temporal variations in albedo, solar irradiance and transmission through the atmosphere. Simplifications concerning the temporal resolution and aggregation procedures of input data were evaluated.The results highlight the importance of spatial and temporal variations in determining the climate impact of albedo change in LCA. Irradiance and atmospheric transmittance depend on season, latitude and climate zone, and they co-vary with instantaneous albedo. Ignoring these dependencies led to case-specific errors in radiative forcing. Extreme errors doubled the climate cooling of albedo change or resulted in warming rather than cooling in two Swedish cases considered. Further research is needed to understand how different land use strategies affect the climate due to albedo, and how this compares to the effect of greenhouse gases. Given that albedo change and greenhouse gases act on different time scales, LCAs can provide better information in relation to climate targets if the timing of flows is considered in life cycle inventory analysis and impact assessment.  相似文献   

19.
Atmospheric aerosols were collected during the scientific expedition to Mt. Qomolangma (Everest) in May–June, 2005. The elemental concentrations of the aerosols were determined by inductively coupled plasma mass spectrometry. This yielded data for the concentration of 14 elements: Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, and Pb. The mean elemental concentrations were generally comparable with those from central Asia and the Arctic, while much higher than those from Antarctic. Size, morphology, and chemical composition of 900 individual aerosol particles were determined by scanning electron microscopy and energy-dispersive X-ray microanalysis. Based on morphology and elemental composition, the particles were clustered into eight groups: soot (8%), tar ball (3%), alumosilicates/silica (55%), calcium sulfate (16%), Ca/Mg carbonate (2%), Fe/Ti-rich particles (3%), Pb-rich particles (1%), and biological particles (12%). The sampling site, located at 6,520 m in the Himalayas, is particularly remote and located at high altitude. Nonetheless, high aerosol enrichment factors for copper, chromium, lead, nickel, vanadium, and zinc all suggest the influence of long-range transported pollution, while enrichment in calcium and the presence of alumino-silicates in individual particle analyses indicates a distinct mineral dust influence. The backward air mass trajectories showed that the northwestern part of India may contribute to the atmospheric aerosol in the central high Himalayas.  相似文献   

20.
利用葵花8(Himawari-8,H8)16个波段数据、卫星、太阳角度数据和深度学习技术,提出一种基于深度全连接网络(Deep Neural Networks,DNN)模型的AOD遥感反演方法(Himawari-DNN)。该方法直接建立H8影像本身与AERONET站点AOD数据间的关系,可避免传统AOD遥感反演方法中复杂过程,得到精度较高的反演结果。通过有效数据对所构建的模型做精度测试,同时将反演结果和实测数据对比分析,结果表明,模型反演结果与研究区内所有站点的观测值均具有较高的一致性(R^2均>0.89)。可见,应用DNN对H8气象静止卫星开展AOD反演具有一定的可行性。  相似文献   

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