Trend analysis of atmospheric aerosols enhances confidence in the evaluation of both direct and indirect effects of aerosols on regional climate change. To comprehensively achieve this over East Africa, it’s importan...Trend analysis of atmospheric aerosols enhances confidence in the evaluation of both direct and indirect effects of aerosols on regional climate change. To comprehensively achieve this over East Africa, it’s important to understand aerosols temporal characteristics over well selected sites namely Nairobi (1°S, 36°E), Mbita (0°S, 34°E), Mau Forest (0.0°S - 0.6°S;35.1°E - 35.7°E), Malindi (2°S, 40°E), Mount Kilimanjaro (3°S, 37°E) and Kampala (0°N, 32.1°E). In this context, trend analysis (annual (in Aerosol Optical Depth (AOD) at 550 nm and Ångström Exponent Anomaly (ÅEA) at 470 - 660 nm) and seasonal (AOD)) from Moderate Resolution Imaging Spectroradiometer (MODIS) were performed following the weighted least squares (WLS) fitting method for the period 2000 to 2013. The MODIS AOD annual trends were ground-truthed by AErosol RObotic NETwork (AERONET) data. Tropical Rainfall Measurement Mission (TRMM) was utilized to derive rainfall rates (RR) in order to assess its influence on the observed aerosol temporal characteristics. The derived annual AOD trends utilizing MODIS and AERONET data were consistent with each other. However, monthly AOD and RR were found to be negatively correlated over Nairobi, Mbita, Mau forest complex and Malindi. There was no clear relationship between the two trends over Kampala and Mount Kilimanjaro, which may imply the role of aerosols in cloud modulation and hence RR received. Seasonality is evident between AOD and ÅEA annual trends as these quantities were observed to be modulated by RR. AOD was observed to decrease over East Africa except Nairobi during the study period as a result of RR during the study period. Unlike the other study sites, Nairobi shows positive trends in AOD that may be attributed to increasing populace and fossil fuel, vehicular-industrial emission and biomass and refuse burning during the study period. Negative trends over the rest of the study sites were associated to rain washout. The AOD and ÅEA derived annual trends were found to meet the statistical significance of 95% confidence level over each study site.展开更多
The atmospheric aerosol absorption capacity is a critical parameter determining its direct and indirect effects on cli- mate. Accurate measurement is highly desired for the study of the radiative budget of the Earth. ...The atmospheric aerosol absorption capacity is a critical parameter determining its direct and indirect effects on cli- mate. Accurate measurement is highly desired for the study of the radiative budget of the Earth. A multi-wavelength （405 rim, 532 nm, 780 nm） aerosol absorption meter based on photoacoustic spectroscopy （PAS） invovling a single cylin- drical acoustic resonator is developed for measuring the aerosol optical absorption coefficients （OACs）. A sensitivity of 1.3 Mm-l （at 532 nm） is demonstrated. The aerosol absorption meter is successfully tested through measuring the OACs of atmospheric nigrosin and ambient aerosols in the suburbs of Hefei city. The absorption cross section and absorption Angstrom exponent （AAE） for ambient aerosol are determined for characterizing the component of the ambient aerosol.展开更多
Seasonal variation of the Tianjin coastal atmospheric aerosol opticalproperties are important for improving the atmosphere correction precision of marinesatellite and learning the environment of the boundary between t...Seasonal variation of the Tianjin coastal atmospheric aerosol opticalproperties are important for improving the atmosphere correction precision of marinesatellite and learning the environment of the boundary between the Bohai Sea and theland. In this paper, the aerosol optical data of Tianjin coastal area from April 2010 toMay 2011 were observed by using the CE317 Solar Photometer, and the aerosol opticalproperties were analyzed. The results show that: Aerosol Optical Thickness (AOT)spectra are basically in accord with Angstrom relationship; there are three basic typesof AOT daily variations, which are rising type, levelling type, and declining type; inTianjin Coastland, the mean value of AOT is highest in autumn, which is 0.686. Thevalue is lower in spring and summer, and hits the lowest point in winter. Angstromexponent α increases successively from spring, summer, autumn to winter. Due to thedusty, the angstrom exponent α in spring is lowest, the mean of which is 0.854.Compared with Qingdao Coastland, the atmospheric aerosol optical properties presentcharacteristics of regionality.展开更多
The understanding of aerosol properties in troposphere, especially their behavior near the ground level, is indispensable for precise evaluation of their impact on the Earth’s radiation studies. Although a sunphotome...The understanding of aerosol properties in troposphere, especially their behavior near the ground level, is indispensable for precise evaluation of their impact on the Earth’s radiation studies. Although a sunphotometer or a skyradiometer can provide the aerosol optical thickness (AOT), their application is limited to daytime under near cloud free conditions. In order to attain the multi-wavelength observation for both day- and night-time including cloudy conditions, here we propose a novel monitoring technique by means of simultaneous measurement using a nephelometer (450, 550, and 700 nm), an aethalometer (370, 470, 520, 590, 660, 880, and 950 nm), and a visibility meter (550 nm). On the basis of the multi-wavelength data of scattering and absorption coefficients from the nephelometer and aethalometer, respectively, first we calculate the real-time values of aerosol extinction coefficient in addition to the Angstrom exponent (AE). Then, correction of these values is carried out by comparing the resulting extinction coefficient with the corresponding value obtained from the optical data of visibility-meter. The major reason for this correction is the loss of relatively coarse particles due to the aerodynamic effect as well as evaporation of water content from particles during the sampling procedure. Then, with the ancillary data of vertical aerosol profile obtained with a lidar (532 nm), the temporal change of AOT is estimated. In this way, information from the sampling can be converted to the ambient properties in the atmospheric boundary layer. Furthermore, daytime data from a sunphotometer (368, 500, 675, and 778 nm) and a skyradiometer (340, 380, 400, 500, 675, 870, and 1020 nm) are used to validate the resulting AOT values. From the overall procedure, we can estimate the AE and AOT values from the sampling data, with uncertainties of approximately 5% for AE and 10% for AOT. Such a capability will be useful for studying aerosol properties throughout 24 hours regardless of the solar radiation and cloud coverage.展开更多
The uncertainty in the quantification of aerosol properties such as concentration, size, and composition, spatially and temporally makes regional studies important. Therefore, this study presents seasonal variations o...The uncertainty in the quantification of aerosol properties such as concentration, size, and composition, spatially and temporally makes regional studies important. Therefore, this study presents seasonal variations of aerosol optical properties over Ilorin (8䓠'N, 4䓢'E), Nigeria. Long-term (1998-2013) records of aerosol optical depth (AOD) and angstrom exponent α, from ground-based Aerosol Robotic Network (AERONET) are used to study the seasonal variability, characteristics and types of aerosol. The study showed that seasonal variations (Harmattan and Summer) result in different aerosol concentration, characteristics, and types. The magnitude and sensitivity of AOD to wavelength are found low in Summer with significant increase during Saharan dust transport season (Harmattan). The average mean AODs are 0.73 ± 0.50, 0.97 ± 0.52 and 0.46 ± 0.29 with corresponding mean angstrom of 0.66 ± 0.36, 0.68 ± 0.34, and 0.64 ± 0.37 for the entire period, Harmattan and Summer seasons. High frequency of occurrence of angstrom exponent below 1 (78% and 81%) which were observed during Harmattan and Summer indicates that the particles are generally coarse in mode. The results revealed that for both Harmattan and Summer seasons, the dominant aerosol was dust (DA) with frequency of occurrence of 82% and 79%. However, mixed aerosol (MIXA) (14.4%) is the second dominant case during Harmattan while in Summer maritime aerosol (MA) (9.1%) associated with transport due to southwesterly trade wind is the second dominant aerosol. This conclusion is supported by size distribution data for the study site which showed that large volume of aerosol particle size are enclosed in largely coarse mode range in all seasons. A 7-day back trajectory seasonal frequency plot sourced from the Hysplit Single Particles Lagrangian Integrated Trajectory model (Hysplit_4 model) shows that dust are transported from the Sahara during north-easterly trade wind flow while the observed marine aerosols are conveyed by the southwesterly trade wind influences to the study site.展开更多
Recent vigorous industrialization and urbanization in Shandong Peninsula,China,have resulted in the emission of heavy anthropogenic aerosols over the region.The annual means of aerosol optical depth(AOD),Angstrom expo...Recent vigorous industrialization and urbanization in Shandong Peninsula,China,have resulted in the emission of heavy anthropogenic aerosols over the region.The annual means of aerosol optical depth(AOD),Angstrom exponent(α),single-scattering albedo(SSA),aerosol direct radiative forcing(ARF),surface radiative forcing(SRF),and top-of-the atmospheric radiative forcing(TOA) recorded during 2004–2011 were respectively 0.67±0.19,1.25±0.24,0.93±0.03,47±9 W m-2,-61±9 W m-2,and-14±8 W m-2.The aerosol optical properties and ARF characteristics showed remarkable seasonal variations due to cycle changes in the aerosol components and dominance type.The atmosphere-surface system was cooled by ARF in all years of the study due to anthropogenic sulfate and nitrate emission and sea salt aerosols.The magnitude of TOA cooling was larger in summer(-15±17 W m-2) and autumn(-12±7 W m-2) than that in spring(-8±4 W m-2) and winter(-9±10 W m-2).展开更多
Neural network analysis based on Growing Hierarchical Self-Organizing Map (GHSOM) is used to examine Spatial-Temporal characteristics in Aerosol Optical Depth (AOD), Ångström Exponent (ÅE)...Neural network analysis based on Growing Hierarchical Self-Organizing Map (GHSOM) is used to examine Spatial-Temporal characteristics in Aerosol Optical Depth (AOD), Ångström Exponent (ÅE) and Precipitation Rate (PR) over selected East African sites from 2000 to 2014. The selected sites of study are Nairobi (1°S, 36°E), Mbita (0°S, 34°E), Mau Forest (0.0° - 0.6°S;35.1°E - 35.7°E), Malindi (2°S, 40°E), Mount Kilimanjaro (3°S, 37°E) and Kampala (0°N, 32.1°E). GHSOM analysis reveals a marked spatial variability in AOD and ÅE that is associated to changing PR, urban heat islands, diffusion, direct emission, hygroscopic growth and their scavenging from the atmosphere specific to each site. Furthermore, spatial variability in AOD, ÅE and PR is distinct since each variable corresponds to a unique level of classification. On the other hand, GHSOM algorithm efficiently discriminated by means of clustering between AOD, ÅE and PR during Long and Short rain spells and dry spell over each variable emphasizing their temporal evolution. The utilization of GHSOM therefore confirms the fact that regional aerosol characteristics are highly variable be it spatially or temporally and as well modulated by PR received over each variable.展开更多
Lidar ratios and AngstrOm exponents of continental,maritime,and desert aerosols were calculated to evaluate the effects of aerosol composition on these parameters.Their correlation was assessed using correlation analy...Lidar ratios and AngstrOm exponents of continental,maritime,and desert aerosols were calculated to evaluate the effects of aerosol composition on these parameters.Their correlation was assessed using correlation analysis and curve fitting.The Pearson correlation coefficient between the lidar ratio and the AngstrOm exponent was larger than 0.95 in all cases.We verified the reliability of the Pearson correlation coefficient using the significance test.The relationship between the lidar ratio and the Angstrom expo- nent of continental aerosol can be described by a cubic polynomial model;thus,the function relation between the change in lidar ratios at different laser wavelengths depends on the fitting coefficients and the AngstrOm exponent.The relationship between the lidar ratio and the AngstrOm exponent of both maritime and desert aerosols can be described by a linear model.In these aerosols,the linear change in lidar ratios at different laser wavelengths remains unaffected by the AngstrOm exponent.The changes in the lidar ratio in maritime aerosol at 355nm and 532nm are -0.7times and -0.18times that at 1064nm, respectively.For desert aerosol,the changes in the lidar ratio at 355nm and 532nm are 0.37 times and 1.88times that at 1064nm,respectively.展开更多
为研究徐州冬季雾-霾天气形成过程中颗粒物粒径及气溶胶光学特性的变化特征,分析了2014年12月1日-2015年2月28日徐州大气颗粒物质量浓度（PM（10）、PM（2.5）、PM1）、数浓度（0-1μm、1-2.5μm、2.5-10μm）和气溶胶光学特性等数据....为研究徐州冬季雾-霾天气形成过程中颗粒物粒径及气溶胶光学特性的变化特征,分析了2014年12月1日-2015年2月28日徐州大气颗粒物质量浓度（PM（10）、PM（2.5）、PM1）、数浓度（0-1μm、1-2.5μm、2.5-10μm）和气溶胶光学特性等数据.结果表明：0-1μm粒径范围细颗粒物的大量增多是引发徐州冬季雾-霾天气的主要因素,徐州冬季地面风速小（静风或轻风天气）,较高的大气相对湿度对雾-霾的形成和维持起着重要影响作用.持续时间较长的雾霾天气,因颗粒物吸湿增长和水汽附着,1-10μm粒径范围大气颗粒物在雾霾时段易发生沉降而减少,后随相对湿度降低雾霾转为短时间的霾天气,1-10μm颗粒物数浓度大幅上升.徐州冬季500nm波段AOD total和AOD fine mode具有相同的变化趋势,雾-霾日AOD total和AOD fine mode显著高于非霾日.AOD fine mode与AOD coarse mode的比值雾-霾日亦明显高于非霾日,而且在雾-霾日Angstrom波长指数主要集中在1-1.6,表明徐州冬季雾-霾时段大气中细颗粒物为主控粒子.展开更多
文摘Trend analysis of atmospheric aerosols enhances confidence in the evaluation of both direct and indirect effects of aerosols on regional climate change. To comprehensively achieve this over East Africa, it’s important to understand aerosols temporal characteristics over well selected sites namely Nairobi (1°S, 36°E), Mbita (0°S, 34°E), Mau Forest (0.0°S - 0.6°S;35.1°E - 35.7°E), Malindi (2°S, 40°E), Mount Kilimanjaro (3°S, 37°E) and Kampala (0°N, 32.1°E). In this context, trend analysis (annual (in Aerosol Optical Depth (AOD) at 550 nm and Ångström Exponent Anomaly (ÅEA) at 470 - 660 nm) and seasonal (AOD)) from Moderate Resolution Imaging Spectroradiometer (MODIS) were performed following the weighted least squares (WLS) fitting method for the period 2000 to 2013. The MODIS AOD annual trends were ground-truthed by AErosol RObotic NETwork (AERONET) data. Tropical Rainfall Measurement Mission (TRMM) was utilized to derive rainfall rates (RR) in order to assess its influence on the observed aerosol temporal characteristics. The derived annual AOD trends utilizing MODIS and AERONET data were consistent with each other. However, monthly AOD and RR were found to be negatively correlated over Nairobi, Mbita, Mau forest complex and Malindi. There was no clear relationship between the two trends over Kampala and Mount Kilimanjaro, which may imply the role of aerosols in cloud modulation and hence RR received. Seasonality is evident between AOD and ÅEA annual trends as these quantities were observed to be modulated by RR. AOD was observed to decrease over East Africa except Nairobi during the study period as a result of RR during the study period. Unlike the other study sites, Nairobi shows positive trends in AOD that may be attributed to increasing populace and fossil fuel, vehicular-industrial emission and biomass and refuse burning during the study period. Negative trends over the rest of the study sites were associated to rain washout. The AOD and ÅEA derived annual trends were found to meet the statistical significance of 95% confidence level over each study site.
基金supported by the Open Research Fund of Key Laboratory of Atmospheric Composition and Optical Radiation,Chinese Academy of Sciencesthe National Natural Science Foundation of China(Grant Nos.41175036 and 41205120)
文摘The atmospheric aerosol absorption capacity is a critical parameter determining its direct and indirect effects on cli- mate. Accurate measurement is highly desired for the study of the radiative budget of the Earth. A multi-wavelength （405 rim, 532 nm, 780 nm） aerosol absorption meter based on photoacoustic spectroscopy （PAS） invovling a single cylin- drical acoustic resonator is developed for measuring the aerosol optical absorption coefficients （OACs）. A sensitivity of 1.3 Mm-l （at 532 nm） is demonstrated. The aerosol absorption meter is successfully tested through measuring the OACs of atmospheric nigrosin and ambient aerosols in the suburbs of Hefei city. The absorption cross section and absorption Angstrom exponent （AAE） for ambient aerosol are determined for characterizing the component of the ambient aerosol.
基金supported by Science Foundation for The Excellent Youth Scholars of Tianjin
文摘Seasonal variation of the Tianjin coastal atmospheric aerosol opticalproperties are important for improving the atmosphere correction precision of marinesatellite and learning the environment of the boundary between the Bohai Sea and theland. In this paper, the aerosol optical data of Tianjin coastal area from April 2010 toMay 2011 were observed by using the CE317 Solar Photometer, and the aerosol opticalproperties were analyzed. The results show that: Aerosol Optical Thickness (AOT)spectra are basically in accord with Angstrom relationship; there are three basic typesof AOT daily variations, which are rising type, levelling type, and declining type; inTianjin Coastland, the mean value of AOT is highest in autumn, which is 0.686. Thevalue is lower in spring and summer, and hits the lowest point in winter. Angstromexponent α increases successively from spring, summer, autumn to winter. Due to thedusty, the angstrom exponent α in spring is lowest, the mean of which is 0.854.Compared with Qingdao Coastland, the atmospheric aerosol optical properties presentcharacteristics of regionality.
文摘The understanding of aerosol properties in troposphere, especially their behavior near the ground level, is indispensable for precise evaluation of their impact on the Earth’s radiation studies. Although a sunphotometer or a skyradiometer can provide the aerosol optical thickness (AOT), their application is limited to daytime under near cloud free conditions. In order to attain the multi-wavelength observation for both day- and night-time including cloudy conditions, here we propose a novel monitoring technique by means of simultaneous measurement using a nephelometer (450, 550, and 700 nm), an aethalometer (370, 470, 520, 590, 660, 880, and 950 nm), and a visibility meter (550 nm). On the basis of the multi-wavelength data of scattering and absorption coefficients from the nephelometer and aethalometer, respectively, first we calculate the real-time values of aerosol extinction coefficient in addition to the Angstrom exponent (AE). Then, correction of these values is carried out by comparing the resulting extinction coefficient with the corresponding value obtained from the optical data of visibility-meter. The major reason for this correction is the loss of relatively coarse particles due to the aerodynamic effect as well as evaporation of water content from particles during the sampling procedure. Then, with the ancillary data of vertical aerosol profile obtained with a lidar (532 nm), the temporal change of AOT is estimated. In this way, information from the sampling can be converted to the ambient properties in the atmospheric boundary layer. Furthermore, daytime data from a sunphotometer (368, 500, 675, and 778 nm) and a skyradiometer (340, 380, 400, 500, 675, 870, and 1020 nm) are used to validate the resulting AOT values. From the overall procedure, we can estimate the AE and AOT values from the sampling data, with uncertainties of approximately 5% for AE and 10% for AOT. Such a capability will be useful for studying aerosol properties throughout 24 hours regardless of the solar radiation and cloud coverage.
文摘The uncertainty in the quantification of aerosol properties such as concentration, size, and composition, spatially and temporally makes regional studies important. Therefore, this study presents seasonal variations of aerosol optical properties over Ilorin (8䓠'N, 4䓢'E), Nigeria. Long-term (1998-2013) records of aerosol optical depth (AOD) and angstrom exponent α, from ground-based Aerosol Robotic Network (AERONET) are used to study the seasonal variability, characteristics and types of aerosol. The study showed that seasonal variations (Harmattan and Summer) result in different aerosol concentration, characteristics, and types. The magnitude and sensitivity of AOD to wavelength are found low in Summer with significant increase during Saharan dust transport season (Harmattan). The average mean AODs are 0.73 ± 0.50, 0.97 ± 0.52 and 0.46 ± 0.29 with corresponding mean angstrom of 0.66 ± 0.36, 0.68 ± 0.34, and 0.64 ± 0.37 for the entire period, Harmattan and Summer seasons. High frequency of occurrence of angstrom exponent below 1 (78% and 81%) which were observed during Harmattan and Summer indicates that the particles are generally coarse in mode. The results revealed that for both Harmattan and Summer seasons, the dominant aerosol was dust (DA) with frequency of occurrence of 82% and 79%. However, mixed aerosol (MIXA) (14.4%) is the second dominant case during Harmattan while in Summer maritime aerosol (MA) (9.1%) associated with transport due to southwesterly trade wind is the second dominant aerosol. This conclusion is supported by size distribution data for the study site which showed that large volume of aerosol particle size are enclosed in largely coarse mode range in all seasons. A 7-day back trajectory seasonal frequency plot sourced from the Hysplit Single Particles Lagrangian Integrated Trajectory model (Hysplit_4 model) shows that dust are transported from the Sahara during north-easterly trade wind flow while the observed marine aerosols are conveyed by the southwesterly trade wind influences to the study site.
基金supported by the National Natural Science Foundation of China(41222033,41375036,and 41105103)and the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA05100102 and XDB05020103)
文摘Recent vigorous industrialization and urbanization in Shandong Peninsula,China,have resulted in the emission of heavy anthropogenic aerosols over the region.The annual means of aerosol optical depth(AOD),Angstrom exponent(α),single-scattering albedo(SSA),aerosol direct radiative forcing(ARF),surface radiative forcing(SRF),and top-of-the atmospheric radiative forcing(TOA) recorded during 2004–2011 were respectively 0.67±0.19,1.25±0.24,0.93±0.03,47±9 W m-2,-61±9 W m-2,and-14±8 W m-2.The aerosol optical properties and ARF characteristics showed remarkable seasonal variations due to cycle changes in the aerosol components and dominance type.The atmosphere-surface system was cooled by ARF in all years of the study due to anthropogenic sulfate and nitrate emission and sea salt aerosols.The magnitude of TOA cooling was larger in summer(-15±17 W m-2) and autumn(-12±7 W m-2) than that in spring(-8±4 W m-2) and winter(-9±10 W m-2).
基金This work was supported by the National Council for Science and Technology Grant funded by the Government of Kenya(NCST/ST&I/RCD/4TH call PhD/201).
文摘Neural network analysis based on Growing Hierarchical Self-Organizing Map (GHSOM) is used to examine Spatial-Temporal characteristics in Aerosol Optical Depth (AOD), Ångström Exponent (ÅE) and Precipitation Rate (PR) over selected East African sites from 2000 to 2014. The selected sites of study are Nairobi (1°S, 36°E), Mbita (0°S, 34°E), Mau Forest (0.0° - 0.6°S;35.1°E - 35.7°E), Malindi (2°S, 40°E), Mount Kilimanjaro (3°S, 37°E) and Kampala (0°N, 32.1°E). GHSOM analysis reveals a marked spatial variability in AOD and ÅE that is associated to changing PR, urban heat islands, diffusion, direct emission, hygroscopic growth and their scavenging from the atmosphere specific to each site. Furthermore, spatial variability in AOD, ÅE and PR is distinct since each variable corresponds to a unique level of classification. On the other hand, GHSOM algorithm efficiently discriminated by means of clustering between AOD, ÅE and PR during Long and Short rain spells and dry spell over each variable emphasizing their temporal evolution. The utilization of GHSOM therefore confirms the fact that regional aerosol characteristics are highly variable be it spatially or temporally and as well modulated by PR received over each variable.
基金National Natural Science Foundation of China grants:No.61405158and No.41627807.
文摘Lidar ratios and AngstrOm exponents of continental,maritime,and desert aerosols were calculated to evaluate the effects of aerosol composition on these parameters.Their correlation was assessed using correlation analysis and curve fitting.The Pearson correlation coefficient between the lidar ratio and the AngstrOm exponent was larger than 0.95 in all cases.We verified the reliability of the Pearson correlation coefficient using the significance test.The relationship between the lidar ratio and the Angstrom expo- nent of continental aerosol can be described by a cubic polynomial model;thus,the function relation between the change in lidar ratios at different laser wavelengths depends on the fitting coefficients and the AngstrOm exponent.The relationship between the lidar ratio and the AngstrOm exponent of both maritime and desert aerosols can be described by a linear model.In these aerosols,the linear change in lidar ratios at different laser wavelengths remains unaffected by the AngstrOm exponent.The changes in the lidar ratio in maritime aerosol at 355nm and 532nm are -0.7times and -0.18times that at 1064nm, respectively.For desert aerosol,the changes in the lidar ratio at 355nm and 532nm are 0.37 times and 1.88times that at 1064nm,respectively.
文摘为研究徐州冬季雾-霾天气形成过程中颗粒物粒径及气溶胶光学特性的变化特征,分析了2014年12月1日-2015年2月28日徐州大气颗粒物质量浓度（PM（10）、PM（2.5）、PM1）、数浓度（0-1μm、1-2.5μm、2.5-10μm）和气溶胶光学特性等数据.结果表明：0-1μm粒径范围细颗粒物的大量增多是引发徐州冬季雾-霾天气的主要因素,徐州冬季地面风速小（静风或轻风天气）,较高的大气相对湿度对雾-霾的形成和维持起着重要影响作用.持续时间较长的雾霾天气,因颗粒物吸湿增长和水汽附着,1-10μm粒径范围大气颗粒物在雾霾时段易发生沉降而减少,后随相对湿度降低雾霾转为短时间的霾天气,1-10μm颗粒物数浓度大幅上升.徐州冬季500nm波段AOD total和AOD fine mode具有相同的变化趋势,雾-霾日AOD total和AOD fine mode显著高于非霾日.AOD fine mode与AOD coarse mode的比值雾-霾日亦明显高于非霾日,而且在雾-霾日Angstrom波长指数主要集中在1-1.6,表明徐州冬季雾-霾时段大气中细颗粒物为主控粒子.
