共查询到20条相似文献，搜索用时 31 毫秒
1.
Kuwait was exposed to a severe dust storm on 19 March 2003, the eve of operation ??Iraqi Freedom??. Three days of dust events (19, 26, 27 March) were analyzed for their aerosol optical and physical properties using ground-based and satellite-retrieved measurements. Ground-based measurements of aerosol optical depth (or thickness; AOD or AOT) at 675?nm, ?? 657, ?ngstrom coefficient ?? 936/657, particulate matter of diameter 10???m or less, PM10 (??g/m3), and meteorological parameters were analyzed for March 2003. AOT exceeded 3 for the 3?days of interest and PM10 concentrations reached as high value as 2,457???g/m3 on 19 March dust storm day. Retrieved aerosol characteristics from space using Moderate Resolution Imaging Spectrometer (MODIS) on board Terra and Aqua satellite were examined against ground-based measurements. A strong correlation was found between ground-based measurements of ?? 675 and the Terra-MODIS retrieved AOD550. The synoptic of the dust storm were analyzed and source regions were identified using back trajectory analysis and Total Ozone Mapping Spectrometer Aerosol Index. 相似文献
2.
Aerosol optical depth (AOD) is a common indicator applied in monitoring aerosols in the atmosphere. The hilly landscape and rapid economic growth of the megacity Chongqing have facilitated increased aerosol concentration, and it is meaningful to accurately retrieve AOD over Chongqing. The HJ-1A/B satellite of China carries a sensor/camera called the Charge Coupled Device (CCD), the spatial resolution of which meets the requirement for retrieving high resolution AOD. In this paper, analysis of the AOD retrievals from different methods using the HJ-1 satellite data revealed the most suitable algorithm. Through comparison with the AOD product of Moderate Resolution Imaging Spectroradiometer (MODIS), the AOD retrieval results using enhanced vegetation index (EVI) to estimate dark pixels showed the highest correlation. The continental aerosol model was used to build a lookup table that was able to facilitate a good AOD retrieval for both city and rural areas. Finally, the algorithm that combined dark pixels, buffer areas, and the deep blue algorithm was found to be most suitable for AOD retrieval. The AOD retrieval results based on the HJ-1 data were consistent with MODIS products, and our algorithm yields reasonable results in most cases. The results were also compared with ground-based PM10 measurements synchronized with the overpass time of the HJ-1 satellite, and high correlation was found. The findings are relevant to other Chinese satellite data used for retrieving AOD on the same channels. 相似文献
3.
K. V. S. Badarinath Shailesh Kumar Kharol T. R. Kiran Chand K. Madhavi Latha 《Meteorology and Atmospheric Physics》2011,111(1-2):65-73
Every year during winter months (December?CJanuary) fog formation over Indo-Gangetic plains (IGP) of Indian region is believed to create numerous hazards. The present study addresses variations in aerosol optical properties, aerosol mass concentration and their impact on solar irradiance for pre-during-post fog conditions of December 2004 over IGP, India. Continuous measurements on aerosol optical depth (AOD), total aerosol mass concentration, black carbon (BC) aerosols, UVery and UVA were carried out for pre, during and post fog periods over study site of Allahabad, India, during December 2004 as a part of Aerosol Land Campaign-II conducted by Indian Space Research Organization (ISRO). High aerosol mass concentrations were observed during fog and post-fog periods. Accumulation mode particle loading was found to be high during pre-fog period and coarse mode particle loading was observed to be high during fog and post-fog periods. Considerable reduction in UVery and UVA irradiance was observed during fog period compared with pre and post-fog periods. Analysis of NOAA-HYSPLIT model runs suggested that enhanced biomass burning episodes down-wind to the study area increased the concentration of AOD and BC. 相似文献
4.
Singh Shishir Kumar Radhakrishnan S. R. Jaswant Mishra Sumit Kumar Shukla Devesh Kumar Ranjan Ashish Sharma Chhemendra 《Journal of Atmospheric Chemistry》2022,79(2):117-139
A Raman lidar system was operated along with the Microtops sunphotometer measurements to carry out the study of the variation of the optical properties of aerosols over Palampur (32.11° N and 76.53° E), India from 17th April to 11th May 2019. The lidar system is furnished with Raman (N2) channel and depolarization channel allowing independent measurement of Lidar Ratio (LR) and linear depolarization ratio. The study reveals that the majority of the aerosols approximately were restricted within the planetary boundary layer (PBL) and very less loading was present in the free troposphere over the study location. The particle loading over the study period was found to be very less with aerosol backscatter coefficient (at 355 nm) ranging from ～0.13 Mm?1sr?1 to ～7.25 Mm?1sr?1 with mean value of 2.67?±?0.82 Mm?1sr?1 and it is well supplemented by the mean aerosol optical depth (AOD) of 0.37?±?0.13 obtained from Microtops Sunphotometer. The average lidar ratio values for 0-1 km altitude (L1) 72?±?13sr, for 1-2 km (L2) altitude 55?±?8sr, for 2-3 km (L3) 54?±?15sr were observed as suggesting dominance of the biomass burning aerosols and anthropogenic aerosols. The particle depolarization ratio (355 nm) values were found from approximately 4.8?±?2.7% to 11.5?±?1.9% with the mean value of 7?±?1.3% suggesting the presence of non-spherical particles. To trace the sources of the pollution, we derived the HYSPLIT trajectory which shows the majority of the movement was from local sources.
相似文献5.
D. Ganguly R. Ray N. Majumdar C. Chowdhury T. K. Jana 《Journal of Atmospheric Chemistry》2018,75(3):319-333
Temporal variations in atmospheric hydrogen sulphide concentrations and its biosphere-atmosphere exchanges were studied in the World’s largest mangrove ecosystem, Sundarbans, India. The results were used to understand the possible contribution of H2S fluxes in the formation of atmospheric aerosol of different size classes (e.g. accumulation, nucleation and coarse mode). The mixing ratio of hydrogen sulphide (H2S) over the Sundarban mangrove atmosphere was found maximum during the post-monsoon season (October to January) with a mean value of 0.59?±?0.02 ppb and the minimum during pre-monsoon (February to May) with a mean value of 0.26?±?0.01 ppb. This forest acted as a perennial source of H2S and the sediment-air emission flux ranged between 1213?±?276 μg S m?2 d?1(December) and 457?±?114 μg S m?2 d?1 (August) with an annual mean of 768?±?240 μg S m?2d?1. The total annual emissions of H2S from the Indian Sundarban were estimated to be 1.2?±?0.6 Tg S. The accumulation mode of aerosols was found to be more enriched with non-sea salt sulfate with an average loading of 5.74 μg m?3 followed by the coarse mode (5.18 μg m?3) and nucleation mode (1.18 μg m?3). However, the relative contribution of Non-sea salt sulfate aerosol to total sulfate aerosol was highest in the nucleation mode (83%) followed by the accumulation (73%) and coarse mode (58%). Significant positive relations between H2S flux and different modes of NSS indicated the likely link between H2S, a dominant precursor for the non-sea salt sulfate, and non-sea sulfate aerosol particles. An increase in H2S emissions from the mangrove could result in an increase in enhanced NSS in aerosol and associated cloud albedo, and a decrease in the amount of incoming solar radiation reaching the Sundarban mangrove forest. 相似文献
6.
Manoj Kumar Anil Kumar Chinmay Mallik N. C. Mahanti A. M. Shekh 《Meteorology and Atmospheric Physics》2011,111(1-2):55-64
The annual variation in planetary boundary layer (PBL) height is determined from the profiles of conserved thermodynamic variables, i.e., virtual potential temperature ?? v and equivalent potential temperature ?? e, using radiosonde data at per-humid climate region, Ranchi (23°42??N, 85°33??E, 610?m asl) and semi-arid region, Anand (23°35??N, 72°55??E, 45.1?m asl), India. Of all the variables, the ?? v profile seems to provide the most reasonable estimate of the PBL height. This has been supplemented by T-Phi gram analysis for specific days. It has been found that in winter the height of boundary layer is very low due to subsidence and radiational cooling, while pre-monsoon months exhibit the most variable convection. It may be inferred that synoptic conditions accompanied by a variety of weather phenomena such as thunderstorms, onset and withdrawal of monsoons, etc. control the ABL over Ranchi, while daytime solar insolation and nighttime radiative cooling mainly control the ABL over Anand. 相似文献
7.
An extensive aerosol sampling program was conducted during January-December 2006 over Kolkata (22o33?? N and 88o20?? E), a mega-city in eastern India in order to understand the sources, distributions and properties of atmospheric fine mode aerosol (PM2.5). The primary focus of this study is to determine the relative contribution of natural and anthropogenic as well as local and transported components to the total fine mode aerosol loading and their seasonal distributions over the metropolis. The average concentrations of fine mode aerosol was found to be 71.2?±?25.2???gm-3 varying between 34.5???gm-3 in monsoon and 112.6???gm-3 in winter. The formation pathways of major secondary aerosol components like nitrate and sulphate in different seasons are discussed. A long range transport of dust aerosol from arid and semi-arid regions of western India and beyond was observed during pre-monsoon which significantly enriched the total aerosol concentration. Vehicular emissions, biomass burning and transported dust particles were the major sources of PM2.5 from local and continental regions whereas sea-salt aerosol was the major source of PM2.5 from marine source regions. 相似文献
8.
Measurements of the broadband global solar radiation (R S) and total ultraviolet radiation (the sum of UV-A and UV-B) were conducted from 2005 to 2010 at 9 sites in arid and semi-arid regions of China. These data were used to determine the temporal variability of UV and UV/R S and their dependence on the water vapor content and clearness index. The dependence of UV/R S on aerosol optical depth (AOD) and water vapor content was also investigated. In addition, a simple and efficient empirically model suited for all-weather conditions was developed to estimate UV from R s. The annual average daily UV level in arid and semi-arid areas is 0.61 and 0.59 MJ m?2 d?1, respectively. The highest value (0.66?±?0.25 MJ m?2 d?1) was recorded at an arid area at Linze. The lowest value (0.53?±?0.22 MJ m?2 d?1) was recorded at a semi-arid area at Ansai. The highest daily value of UV radiation was measured in May, whereas the lowest value was measured in December. The monthly variation of the UV/R s ratio ranged from 0.41 in Aksu to 0.35 in Qira. The monthly mean value of UV/R s gradually increased from November and then decreased in August. A small decreasing trend of UV/R s was observed in the arid and semi-arid regions due to recently increasing amounts of fine aerosol. A simple and efficient empirically model suit for all-weather condition was developed to estimate UV from R s. The slope a and intercept b of the regression line between the estimated and measured values were close to 1 and zero, respectively. The relative error between the estimated and measured values was less than 11.5%. Application of the model to data collected from different locations in this region also resulted in reasonable estimates of UV. 相似文献
9.
塔克拉玛干沙漠地区气溶胶光学厚度卫星遥感产品验证 总被引：2，自引：0，他引：2
基于塔克拉玛干沙漠地区地基太阳光度计数据,系统验证2007～2008年星载多角度成像光谱仪(MISR)、中分辨率成像光谱仪(MODIS)和臭氧监测仪(OMI)气溶胶反演产品,旨在定量评估这些产品在我国沙漠地区的气溶胶光学厚度(AOD)反演精度。结果表明:MODIS/AOD的相关系数在4种产品中最高(0.91),OMI/AOD次之(0.87),其次为MISR/AOD(0.84),OMI/UVAI相关系数偏低(0.51)。MISR/AOD均方根误差(0.14)和平均偏差(-0.06)在4种反演产品中最低。与地基观测相比,MISR/AOD、MODIS/AOD系统偏低,OMI/AOD、OMI/UVAI系统偏高。在相同比较条件下(地基观测气溶胶光学厚度值限定在2.0以内),MISR的均方根误差和平均偏差在4种反演产品中最低,且相关系数也较高(0.84)。尽管存在诸多不同,但3种探测器气溶胶反演产品均能较好地展示该地区的气溶胶季节变化。塔克拉玛干沙漠春、夏季AOD较大,秋、冬季AOD相对较小。ngstrm波长指数的结果表明,春季(3～5月)最小(均值为0.11),夏季(6～8月)次之,秋季(9～11月)和冬季(12月至次年2月)较大(均值达到0.61),这表明在春、夏季气溶胶粒子偏大,秋、冬季气溶胶粒子偏小。此外,通过研究2000～2010年AOD年际变化表明,由于塔克拉玛干沙漠地区属于沙尘源区,气溶胶类型较为单一,所以总体来说,变化趋势不是较为明显。从反演结果来看,2003年的气溶胶含量为此10年中最高,年均值达到0.32;2005年的气溶胶含量在这10年中最低,年均值为0.28。 相似文献
10.
Photosynthetically active radiation (Q p ) is a key variable in models of net primary productivity and carbon cycle modelling. The relationship between broadband global solar radiation (R s) and Q p is investigated using 6?years of radiation data collected at 9 sites in arid and semi-arid regions of China. The dependence of Q p /R S on aerosol optical depth (AOD) and water vapour content are also discussed. A simple and efficient all-weather empirically derived model is developed to estimate Q p from R s. The annual average daily Q p in arid and semi-arid areas is 29.9?±?11.7 and 27.3?±?10.1?mol?m-2 d-1, respectively. The highest value (31.9?±?11.3?mol?m-2 d-1) appears at Linze in the arid area. The lowest value (24.3?±?9.7?mol?m-2 d-1) appears at Ansai in the semi-arid area. The results show that the monthly variation of the Q p /R s ratio ranges from 1.69?±?0.19?mol?MJ-1 in Aksu to 1.91?±?0.08?mol?MJ-1 in Fukang. There is a small decreasing trend of the ratio of Q p to R s (PAR fraction) in arid and semi-arid regions because of the recent increase in fine aerosols. A simple and efficient empirically model suit for all-weather condition was developed to estimate Q p from R s. The slope a and intercept b of the regression line between estimated and measured values is close to 1 and zero, respectively. The application of the model to data collected from different locations also results in reasonable estimates of Q p . 相似文献
11.
C. Viatte K. Strong C. Paton-Walsh J. Mendonca N. T. O'Neill J. R. Drummond 《大气与海洋》2013,51(5):522-531
In August 2010, simultaneous enhancements of aerosol optical depth and total columns of carbon monoxide (CO), hydrogen cyanide (HCN), and ethane (C2H6) were observed at the Polar Environment Atmospheric Research Laboratory (PEARL, 80.05°N, ?86.42°W, 0.61 km above sea level, Eureka, Nunavut, Canada). Moderate Resolution Imaging Spectroradiometer (MODIS) hot spots, Ozone Monitoring Instrument (OMI) aerosol index maps, and Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) back-trajectories were used to attribute these enhancements to an intense boreal fire event occurring in Russia. A ground-based Fourier Transform InfraRed (FTIR) spectrometer at PEARL provided vertically integrated measurements of trace gases transported in smoke plumes. We derived HCN and C2H6 equivalent emission ratios with respect to CO of 0.0054?±?0.0022 and 0.0108?±?0.0036, respectively, and converted them into equivalent emission factors of 0.66?±?0.27 g kg?1 and 1.47?±?0.50 g kg?1 (in grams of gas per kilogram of dry biomass burnt, with one-sigma uncertainties). These emission factors add new observations to the relatively sparse datasets available and can be used to improve the simulation of biomass burning fire emissions in chemical transport models. These emission factors for the boreal forest are in agreement with the mean values recently reported in a compilation study. 相似文献
12.
Investigation on the direct radiative effect of fossil fuel black-carbon aerosol over China 总被引：2，自引：1，他引：1
Bingliang Zhuang Fei Jiang Tijian Wang Shu Li Bin Zhu 《Theoretical and Applied Climatology》2011,104(3-4):301-312
In China, due to lack of countrywide monitoring and coarse emission inventory of black carbon (BC) in early years, there are large uncertainties as to the estimations of its loading, direct radiative forcing (DRF) and climate response. Here, we apply an up-to-date emission inventory of BC in 2006 to investigate its loading, optical depth (AOD) at 550?nm and DRF using the coupled Regional Climate Chemistry Modeling System (RegCCMS). A state of the art air quality model (WRF/Chem) is also used to access surface BC concentration. Simulated surface concentrations of BC from these two models were compared with observations, while the AOD was compared with the results both from the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model and from satellite and ground-based simulations. Results show that RegCCMS presented similar patterns and levels of annual mean-surface BC concentration to those of WRF/Chem. The regional distributions and monthly variations of RegCCMS BC were reproduced well in comparison to observations. Simulated pattern of AODs are consistent to but lower than those from satellite (Omi-0.25°) and AERONET simulations. Annual mean DRFs mainly distribute in the area with high BC loadings, with regional mean of 0.75?W?m?C2 and predicted global mean of 0.343?W?m?C2. In general, the results are about 0.4?C5 times for regional column burden, about 2 times as high for regional mean DRFs, about 1.3?C1.8 times for global mean DRFs and about 3?C4 times for AOD at 550?nm as compared to those in previous studies in China. These increasing DRFs of BC imply that its warming effect and climate response should be stronger and the DRF of total aerosols should be weaker (less negative). 相似文献
13.
Sharma Sudhir Kumar Karapurkar Supriya G. Shenoy Damodar M. Mandal Tuhin Kumar 《Journal of Atmospheric Chemistry》2022,79(1):67-79
This study presents the chemical composition (carbonaceous and nitrogenous components) of aerosols (PM2.5 and PM10) along with stable isotopic composition (δ13C and δ15N) collected during winter and the summer months of 2015–16 to explore the possible sources of aerosols in megacity Delhi, India. The mean concentrations (mean?±?standard deviation at 1σ) of PM2.5 and PM10 were 223?±?69 µg m?3 and 328?±?65 µg m?3, respectively during winter season whereas the mean concentrations of PM2.5 and PM10 were 147?±?22 µg m?3 and 236?±?61 µg m?3, respectively during summer season. The mean value of δ13C (range: ??26.4 to ??23.4‰) and δ15N (range: 3.3 to 14.4‰) of PM2.5 were ??25.3?±?0.5‰ and 8.9?±?2.1‰, respectively during winter season whereas the mean value of δ13C (range: ??26.7 to ??25.3‰) and δ15N (range: 2.8 to 11.5‰) of PM2.5 were ??26.1?±?0.4‰ and 6.4?±?2.5‰, respectively during the summer season. Comparison of stable C and N isotopic fingerprints of major identical sources suggested that major portion of PM2.5 and PM10 at Delhi were mainly from fossil fuel combustion (FFC), biomass burning (BB) (C-3 and C-4 type vegitation), secondary aerosols (SAs) and road dust (SD). The correlation analysis of δ13C with other C (OC, TC, OC/EC and OC/WSOC) components and δ15N with other N components (TN, NH4+ and NO3?) are also support the source identification of isotopic signatures.
相似文献14.
Joonsuk Lee Won Jun Choi Deok Rae Kim Seung-Yeon Kim Chang-Keun Song Jun Suk Hong Youdeog Hong Sukjo Lee 《Asia-Pacific Journal of Atmospheric Sciences》2013,49(3):271-278
Surface erythemal UV radiation is mainly affected by total column ozone, aerosols, clouds, and solar zenith angle. The effect of ozone on the surface UV radiation has been explored many times in the previous studies due to the decrease of ozone layer. In this study, we calculated the effect of aerosols on the surface UV radiation as well as that of ozone using data acquired from Ozone Monitoring Instrument (OMI). First, ozone, aerosol optical depth (AOD), and surface erythemal UVB radiation measured from satellite are compared with those from ground measurements. The results showed that the comparison for ozone was good with r 2 of 0.92. For aerosol, there was difference between satellite measurements and surface measurements due to the insufficient information on aerosol in the retrieval algorithm. The r 2 for surface erythemal UV radiation was high (～0.94) but satellite measurements showed about 30% larger values than surface measurements on average by not considering the effect of absorbing aerosols in the retrieval process from satellite measurements. Radiative amplification factor (RAF) is used to access the effect of ozone and aerosol quantitatively. RAF for ozone was 0.97～1.49 with solar zenith angle. To evaluate the effect of aerosol on the surface UV radiation, only clear-sky pixel data were used and solar zenith angle and total column amount of ozone were fixed. Also, RAF for aerosol was assessed according to the single scattering albedo (SSA) of aerosols. The results showed that RAF for aerosol with smaller SSA (< 0.90) was larger than that for with larger SSA (> 0.90). The RAF for aerosol was 0.09～0.22 for the given conditions which was relatively small compared to that for ozone. However, considering the fact that aerosol optical depth can change largely in time and space while the total column amount of ozone does not change very much, it needs to include the effect of aerosol to predict the variations of surface UV radiation more correctly. 相似文献
15.
The photochemical activation of chlorine by dissolved iron in artificial sea-salt aerosol droplets and by highly dispersed iron oxide (Fe2O3) aerosol particles (mainly hematite, specific surface ~150 m2 g?1) exposed to gaseous HCl, was investigated in humidified air in a Teflon simulation chamber. Employing the radical-clock technique, we quantified the production of gaseous atomic chlorine (Cl) from the irradiated aerosol. When the salt aerosol contained Fe2O3 at pH 6, no significant Cl production was observed, even if the dissolution of iron was forced by “weathering” (repeatedly freezing and thawing for five times). Adjusting the pH in the stock suspension to 2.6, 2.2, and 1.9 and equilibrating for one week resulted in a quantifiable amount of dissolved iron (0.03, 0.2, and 0.6 mmol L?1, respectively) and in gaseous Cl production rates of ~1.6, 6, and 8?×?1021 atoms cm?2 h?1, respectively. In a further series of experiments, the pure Fe2O3 aerosol was exposed to various levels of gaseous hydrogen chloride (HCl). The resulting Cl production rates ranged from 8?×?1020 Cl atoms cm?2 h?1 (at ~4 ppb HCl) to 5?×?1022 Cl atoms cm?2 h?1 (at ~350 ppb HCl) and confirmed the uptake and conversion of HCl to atomic Cl (at HCl to Cl conversion yields of 2–5 %, depending on the relative humidity). The Fe2O3 experiments indicate that iron-induced Cl formation may be important for highly soluble combustion-aerosol particles in marine environments in the presence of gaseous HCl. 相似文献
16.
C. Di Biagio A. di Sarra P. Eriksen S. E. Ascanius G. Muscari B. Holben 《Climate Dynamics》2012,39(3-4):953-969
This study is based on ground-based measurements of downward surface shortwave irradiance (SW), columnar water vapour (wv), and aerosol optical depth (τ) obtained at Thule Air Base (Greenland) in 2007–2010, together with MODIS observations of the surface shortwave albedo (A). Radiative transfer model calculations are used in combination with measurements to separate the radiative effect of A (ΔSWA), wv (ΔSWwv), and aerosols (ΔSWτ) in modulating SW in cloud-free conditions. The shortwave radiation at the surface is mainly affected by water vapour absorption, which produces a reduction of SW as low as ?100 Wm?2 (?18%). The seasonal change of A produces an increase of SW by up to +25 Wm?2 (+4.5%). The annual mean radiative effect is estimated to be ?(21–22) Wm?2 for wv, and +(2–3) Wm?2 for A. An increase by +0.065 cm in the annual mean wv, to which corresponds an absolute increase in ΔSWwv by 0.93 Wm?2 (4.3%), has been observed to occur between 2007 and 2010. In the same period, the annual mean A has decreased by ?0.027, with a corresponding decrease in ΔSWA by 0.41 Wm?2 (?14.9%). Atmospheric aerosols produce a reduction of SW as low as ?32 Wm?2 (?6.7%). The instantaneous aerosol radiative forcing (RFτ) reaches values of ?28 Wm?2 and shows a strong dependency on surface albedo. The derived radiative forcing efficiency (FEτ) for solar zenith angles between 55° and 70° is estimated to be (?120.6 ± 4.3) for 0.1 < A < 0.2, and (?41.2 ± 1.6) Wm?2 for 0.5 < A < 0.6. 相似文献
17.
Kasturi Devi Kanniah Jason Beringer Nigel J. Tapper Chuck N. Long 《Theoretical and Applied Climatology》2010,100(3-4):423-438
Aerosols have been shown to affect the quantity and quality of solar radiation on the Earth’s surface. Savanna regions are subject to frequent burning and release of aerosols that may impact on radiation components and possibly vegetation productivity in this region. Therefore, in this study, we have analyzed the optical properties of aerosols (aerosol optical depth (AOD) and Angstrom coefficient) from the Atmospheric Radiation Measurement site in Darwin for the periods from April 2002 to June 2005 as measured by a multifilter rotating shadowband radiometer. The influence of aerosols and their effect on surface shortwave incoming solar radiation and savanna productivity were examined for the dry season using sky radiation collection of radiometers and eddy covariance measurements from the Howard Springs flux site. Results indicated that aerosol concentrations in the region were relatively low compared to other savanna regions with the maximum monthly average AOD over the period being the greatest in October (0.29?±?0.003 standard error at 500 nm). The highest monthly average Angstrom exponent was also found in October (1.38?±?0.008). The relatively low aerosol concentration in this region can be attributed to the mixture of smoke aerosols with humidity haze and local circulations. Over a range of AODs from 0.1 to 0.4, we found a modest increase in the fraction of diffuse radiation to total radiation from 11% to 21%. This small increase in diffuse fraction did not affect the carbon flux significantly. However, because the current range of AOD in the region is relatively low, the region could be sensitive to increases in aerosols and diffuse fraction in the future. 相似文献
18.
Himawari-8是由日本气象局发射的新一代静止气象卫星，其搭载的传感器AHI（Advanced Himawari Imager）可实现10 min/次的高时间分辨率对地观测。本文将2015年9月至2017年12月Himawari-8卫星Level-2气溶胶光学厚度（AOD）产品与AERONET（AErosol RObotic NETwork）70个站点的地基观测数据进行对比验证分析，结果表明Himawari-8卫星反演的气溶胶光学厚度产品的精度存在很大的空间上的差异性，其中有48个站点Himawari-8 AOD与AERONET AOD之间存在较好的相关性（R>0.5），有22个站点Himawari-8卫星反演气溶胶光学厚度产品存在明显的低估现象。在American_Samoa、Bandung、Birdsville、Bukit_Kototabang、Canberra、Fowlers_Gap、Jabiru以及QOMS_CAS等站点出现地基观测值很小而卫星反演的气溶胶光学厚度较大的情况。对绝对误差（Himawari-8 AOD与AERONET AOD的差）进行分析发现Himawari-8 AOD存在低估现象时绝对误差与AERONET AOD之间存在较好的相关性；在地基观测值很小而Himawari-8卫星反演AOD较大的地区绝对误差与Himawari-8 AOD之间存在较好的线性关系，这为Himawari-8 AOD反演算法的改进与完善提供了有用的研究发现。 相似文献
19.
《Atmospheric Research》2009,91(2-4):211-222
The microphysical structure, chemical composition and prehistory of aerosol are related to the aerosol optical properties and radiative effect in the UV spectral range. The aim of this work is the statistical mapping of typical aerosol scenarios and adjustment of regional aerosol parameters. The investigation is based on the in situ measurements in Preila (55.55° N, 21.00° E), Lithuania, and the AERONET data from the Gustav Dalen Tower (58 N, 17 E), Sweden.Clustering of multiple characteristics enabled to distinguish three aerosol types for clear-sky periods: 1) clean maritime–continental aerosol; 2) moderately polluted maritime–continental aerosol; 3) polluted continental aerosol. Differences between these types are due to significant differences in aerosol number and volume concentration, effective radius of volume distribution, content of SO4− ions and Black Carbon, as well as different vertical profiles of atmospheric relative humidity. The UV extinction, aerosol optical depth (AOD) and the Ångstrom coefficient α increased with the increasing pollution. The value α = 1.96 was observed in the polluted continental aerosol that has passed over central and eastern Europe and southern Russia. Reduction of the clear-sky UV index against the aerosol-free atmosphere was of 4.5%, 27% and 41% for the aerosol types 1, 2 and 3, respectively. 相似文献
20.
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