气候变化背景下进一步开展高污染地区气溶胶直接辐射效应的研究,对于该地区的大气环境监测、气候变化评估以及农业生产布局等具有重要意义。利用全球气溶胶监测网(AERONET)多年观测资料以及MODIS地表反照率数据,借助6S(Second Simulatio...气候变化背景下进一步开展高污染地区气溶胶直接辐射效应的研究,对于该地区的大气环境监测、气候变化评估以及农业生产布局等具有重要意义。利用全球气溶胶监测网(AERONET)多年观测资料以及MODIS地表反照率数据,借助6S(Second Simulation of a Satellite Signal in the Solar Spectrum)辐射传输模式,定量评估2001年1月-2016年12月中国AERONET北京、香河和太湖3个典型高污染站点多年晴空条件下的气溶胶直接辐射效应。结果表明:(1)各个高污染站点气溶胶PM2.5质量浓度季节变化特征差异明显,秋冬污染较为严重,其中高值主要集中在1月、2月、11月和12月;(2)与无气溶胶影响相比,气溶胶致使各站点地表直接辐射年际变化较明显。在气溶胶影响下,北京、香河和太湖3个站点2001-2016年地表日平均直接辐射年际变化较明显,均呈波动增加趋势,且香河站日平均直接辐射增加最大(621.14W·m-2),太湖站次之(743.29W·m-2),北京站最小(488.14W·m-2)。(3)气溶胶影响下各站点地表直接辐射明显降低,且气溶胶对各站点影响差异较大。2001-2016年,北京、太湖和香河站年平均地表直接辐射分别降低32.29%、24.01%和15.07%。其中,气溶胶对北京站的地表直接辐射影响最大,香河站最小。(4)近15a来,北京、香河和太湖3个站点气溶胶地表辐射效应均呈现增加趋势。展开更多
Taking winter and summer in eastern China as an example application, a grid-cell method of aerosol direct radiative forcing（ADRF） calculation is examined using the Santa Barbara DISORT Atmospheric Radiative Transfer...Taking winter and summer in eastern China as an example application, a grid-cell method of aerosol direct radiative forcing（ADRF） calculation is examined using the Santa Barbara DISORT Atmospheric Radiative Transfer（SBDART） model with inputs from MODIS and AERONET observations and reanalysis data. Results show that there are significant seasonal and regional differences in climatological mean aerosol optical parameters and ADRF. Higher aerosol optical depth（AOD）occurs in summer and two prominent high aerosol loading centers are observed. Higher single scattering albedo（SSA） in summer is likely associated with the weak absorbing secondary aerosols. SSA is higher in North China during summer but higher in South China during winter. Aerosols induce negative forcing at the top of the atmosphere（TOA） and surface during both winter and summer, which may be responsible for the decrease in temperature and the increase in relative humidity.Values of ADRF at the surface are four times stronger than those at the TOA. Both AOD and ADRF present strong interannual variations; however, their amplitudes are larger in summer. Moreover, patterns and trends of ADRF do not always correspond well to those of AOD. Differences in the spatial distributions of ADRF between strong and weak monsoon years are captured effectively. Generally, the present results justify that to calculate grid-cell ADRF at a large scale using the SBDART model with observational aerosol optical properties and reanalysis data is an effective approach.展开更多
This paper presents a study using in situ measurements (AERONET data) to characterize the intra-seasonal variability of aerosols and their shortwave radiative impacts on Sahel (11N - 18N and 20W - 15E) climate using a...This paper presents a study using in situ measurements (AERONET data) to characterize the intra-seasonal variability of aerosols and their shortwave radiative impacts on Sahel (11N - 18N and 20W - 15E) climate using a long time series (2000 to 2010) from AERONET data. We first used the MISR aerosol optical depth (AOD) averaged between 2000 and 2010 to identify dust maxima regions. They are mainly located over Eastern Mauritania-Northern Mali and Eastern Niger-Western Tchad (near the Bodele depression). Moreover the aerosol loading is stronger during the spring (MAM) and particularly during the summer (JJA). The analysis of AERONET data at 4 Sahelian stations (Dakar, Agoufou, Banizoumbou and Ouagadougou) shows that Sahel is under dust influence all year long. The dust season is mainly located between March and October, with two peaks of AOD recorded in March and June;while the maximum of biomass burning activity is recorded in winter (December to February). The radiative forcing of aerosols on the Sahelian climate results mainly in a cooling as well as at the surface than at the top of the atmosphere (TOA) but the forcing is stronger at the surface and particularly during the summer (JJA) and spring (MAM) periods. Although there is not a sharp difference between DJF and SON periods from a station to another one when considering the aerosol loading (AOD), the radiative forcing is stronger at the surface and weaker at the TOA during DJF for most stations. The analysis of the force effectiveness (ratio between AOD and the radiative forcing) suggests that the BOA radiative forcing is mainly influenced by the nature of aerosols.展开更多
The probability distribution analysis is per-formed for multi-timescale aerosol optical depth (AOD) using AErosol RObotic NETwork (AERONET) level 2.0 data.The maximum likelihood estimation is employed to determine the...The probability distribution analysis is per-formed for multi-timescale aerosol optical depth (AOD) using AErosol RObotic NETwork (AERONET) level 2.0 data.The maximum likelihood estimation is employed to determine the best-fit probability density function (PDF),and the statement that the fitting Weibull distribution will be light-tailed is proved true for these AOD samples.The best-fit PDF results for multi-site data show that the PDF of AOD samples with longer timescale in most sites tends to be stably represented by lognormal distribution,while Weibull distribution is a better fit for AOD samples with short timescales.The reason for this difference is ana-lyzed through tail characteristics of the two distributions,and an indicator for the selection between Weibull and lognormal distributions is suggested and validated.The result of this research is helpful for determining the most accurate AOD statistics for a given site and a given time-scale and for validating the retrieved AOD through its PDF.展开更多
Collocated data of the moderate resolution imaging spectroradiometer (MO<span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">DIS) Collection 6.1 aerosol o...Collocated data of the moderate resolution imaging spectroradiometer (MO<span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">DIS) Collection 6.1 aerosol optical depths (AOD) at 3 km × 3 km north of 59.9</span><span style="font-family:Verdana;">°</span><span style="font-family:Verdana;">N over ocean were assessed at 550 nm by aerosol robotic network (AERONET) data from coastal sites and marine aerosol network (MAN) data from vessels during June to October 2006 to 2018. Typically, MODIS AOD w</span><span style="font-family:Verdana;">as</span><span style="font-family:Verdana;"> higher at low and lower at high values than the AERONET AOD. Discrepancies were largest for sites where the Earth’s surface around the site is very heterogeneous (Canadian Archipelago, coast of Greenland). Due to the higher likelihood for sea-ice, MAN and MODIS AOD differed stronger west of Greenland and over the Beaufort Sea than at location in the Greenland and Norwegian Seas and Atlantic. MODIS AOD well captured the inter-seasonal variability found in the AERONET AOD data (R = 0.933). At all sites, MO</span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">DIS and AERONET AOD agreement improved as time progressed in the shipping season, hinting at errors in sea-ice vs. open water classification. Overall 75.3% of the MODIS AOD data fell within the limits of the error envelops of the AERONET/MAN AOD data with MAN ranging between 87.5% and 100%. Changes in both MODIS and AERONET mean AOD between two periods of same length (2006-2011, 2013-2018) were explainable by changes in emissions for all sites</span><span style="font-family:Verdana;">.</span>展开更多
This study presents detailed analysis of spatiotemporal variations and trend of dust optical properties i.e., Aerosol Optical Depth(AOD) and Angstrom component over Asian desert regions using thirteen years of data(i....This study presents detailed analysis of spatiotemporal variations and trend of dust optical properties i.e., Aerosol Optical Depth(AOD) and Angstrom component over Asian desert regions using thirteen years of data(i.e., 2001–2013) retrieved from Aerosol Robotic Network(AERONET), Moderate Resolution Imaging Spectroradiometer(MODIS) and Multi-angle Imaging Spectroradiometer(MISR). These regions include Solar Village, Dunhuang and Dalangzadgad and are considered as origin of desert aerosols in Asia. Mann–Kendall trend test was used to show the trend of AOD. The relationship of AOD with weather parameters and general AOD trend over different wavelengths has also been shown. AOD's trend has been observed significant throughout the year in Solar Village, while in Dunhuang and Dalanzadgad the significant trend has been found only in peak period(March–June).Analysis show high values of AOD and low values of angstrom in Solar Village during peak period. In Chinese desert regions, high values of AOD have been found during peak period and low values in pre-peak period. Significant relationship has been observed between AOD and average temperature in Solar Village and Dalanzadgad whereas rainfall and wind speed showed no significant impact on AOD in all desert regions.展开更多
Aerosol Optical Thickness （AOT）, water vapor content and derived Angstrom exponent acquired by a CIMEL sun photometer in Beijing are analyzed. Monthly means computed from quality-assured daily means, seasonal trends...Aerosol Optical Thickness （AOT）, water vapor content and derived Angstrom exponent acquired by a CIMEL sun photometer in Beijing are analyzed. Monthly means computed from quality-assured daily means, seasonal trends and inter-annual variations are presented and discussed. Summer has the highest seasonal average AOT at 440 nm （τa440）, Angstrom exponent （α440-870） and water vapor content with the values 0.93, 1.34 and 3.0 cm, respectively. The second highest seasonal average τa440 appears in spring with the largest variation of α440-870 and minimum α440-870 0.99 due to the impact of coarse particles. The minimum seasonal average τa440 （0.44） and water vapor content （0.4 cm） appear in winter. The annual average τa440 , α440-870 and water vapor content for about 4-year observation period are 0.70, 1.19 and 1.4 cm, respectively. All monthly average Angstrom exponents are within 0.8-1.4. which indicates aerosol in Beijing is a very complex mixture of both fine- and coarse-mode particles （from anthropogenic influence and natural mineral dust）.展开更多
文摘气候变化背景下进一步开展高污染地区气溶胶直接辐射效应的研究,对于该地区的大气环境监测、气候变化评估以及农业生产布局等具有重要意义。利用全球气溶胶监测网(AERONET)多年观测资料以及MODIS地表反照率数据,借助6S(Second Simulation of a Satellite Signal in the Solar Spectrum)辐射传输模式,定量评估2001年1月-2016年12月中国AERONET北京、香河和太湖3个典型高污染站点多年晴空条件下的气溶胶直接辐射效应。结果表明:(1)各个高污染站点气溶胶PM2.5质量浓度季节变化特征差异明显,秋冬污染较为严重,其中高值主要集中在1月、2月、11月和12月;(2)与无气溶胶影响相比,气溶胶致使各站点地表直接辐射年际变化较明显。在气溶胶影响下,北京、香河和太湖3个站点2001-2016年地表日平均直接辐射年际变化较明显,均呈波动增加趋势,且香河站日平均直接辐射增加最大(621.14W·m-2),太湖站次之(743.29W·m-2),北京站最小(488.14W·m-2)。(3)气溶胶影响下各站点地表直接辐射明显降低,且气溶胶对各站点影响差异较大。2001-2016年,北京、太湖和香河站年平均地表直接辐射分别降低32.29%、24.01%和15.07%。其中,气溶胶对北京站的地表直接辐射影响最大,香河站最小。(4)近15a来,北京、香河和太湖3个站点气溶胶地表辐射效应均呈现增加趋势。
基金supported by the Chinese Academy of Sciences Strategic Priority Research Program(Grant No.XDA05100303)the National Natural Science Foundation of China(Grant Nos.41230419,91337213 and 41075041)the Special Funds for Public Welfare of China(Grant No.GYHY201306077)
文摘Taking winter and summer in eastern China as an example application, a grid-cell method of aerosol direct radiative forcing（ADRF） calculation is examined using the Santa Barbara DISORT Atmospheric Radiative Transfer（SBDART） model with inputs from MODIS and AERONET observations and reanalysis data. Results show that there are significant seasonal and regional differences in climatological mean aerosol optical parameters and ADRF. Higher aerosol optical depth（AOD）occurs in summer and two prominent high aerosol loading centers are observed. Higher single scattering albedo（SSA） in summer is likely associated with the weak absorbing secondary aerosols. SSA is higher in North China during summer but higher in South China during winter. Aerosols induce negative forcing at the top of the atmosphere（TOA） and surface during both winter and summer, which may be responsible for the decrease in temperature and the increase in relative humidity.Values of ADRF at the surface are four times stronger than those at the TOA. Both AOD and ADRF present strong interannual variations; however, their amplitudes are larger in summer. Moreover, patterns and trends of ADRF do not always correspond well to those of AOD. Differences in the spatial distributions of ADRF between strong and weak monsoon years are captured effectively. Generally, the present results justify that to calculate grid-cell ADRF at a large scale using the SBDART model with observational aerosol optical properties and reanalysis data is an effective approach.
文摘This paper presents a study using in situ measurements (AERONET data) to characterize the intra-seasonal variability of aerosols and their shortwave radiative impacts on Sahel (11N - 18N and 20W - 15E) climate using a long time series (2000 to 2010) from AERONET data. We first used the MISR aerosol optical depth (AOD) averaged between 2000 and 2010 to identify dust maxima regions. They are mainly located over Eastern Mauritania-Northern Mali and Eastern Niger-Western Tchad (near the Bodele depression). Moreover the aerosol loading is stronger during the spring (MAM) and particularly during the summer (JJA). The analysis of AERONET data at 4 Sahelian stations (Dakar, Agoufou, Banizoumbou and Ouagadougou) shows that Sahel is under dust influence all year long. The dust season is mainly located between March and October, with two peaks of AOD recorded in March and June;while the maximum of biomass burning activity is recorded in winter (December to February). The radiative forcing of aerosols on the Sahelian climate results mainly in a cooling as well as at the surface than at the top of the atmosphere (TOA) but the forcing is stronger at the surface and particularly during the summer (JJA) and spring (MAM) periods. Although there is not a sharp difference between DJF and SON periods from a station to another one when considering the aerosol loading (AOD), the radiative forcing is stronger at the surface and weaker at the TOA during DJF for most stations. The analysis of the force effectiveness (ratio between AOD and the radiative forcing) suggests that the BOA radiative forcing is mainly influenced by the nature of aerosols.
基金supported by funds from the Chinese Global Change Research Program (Grant No.2010CB951804)the National Natural Science Foundation of China (Grant No.40830103)the China Postdoctoral Science Foundation (Grant No.20100480436)
文摘The probability distribution analysis is per-formed for multi-timescale aerosol optical depth (AOD) using AErosol RObotic NETwork (AERONET) level 2.0 data.The maximum likelihood estimation is employed to determine the best-fit probability density function (PDF),and the statement that the fitting Weibull distribution will be light-tailed is proved true for these AOD samples.The best-fit PDF results for multi-site data show that the PDF of AOD samples with longer timescale in most sites tends to be stably represented by lognormal distribution,while Weibull distribution is a better fit for AOD samples with short timescales.The reason for this difference is ana-lyzed through tail characteristics of the two distributions,and an indicator for the selection between Weibull and lognormal distributions is suggested and validated.The result of this research is helpful for determining the most accurate AOD statistics for a given site and a given time-scale and for validating the retrieved AOD through its PDF.
文摘Collocated data of the moderate resolution imaging spectroradiometer (MO<span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">DIS) Collection 6.1 aerosol optical depths (AOD) at 3 km × 3 km north of 59.9</span><span style="font-family:Verdana;">°</span><span style="font-family:Verdana;">N over ocean were assessed at 550 nm by aerosol robotic network (AERONET) data from coastal sites and marine aerosol network (MAN) data from vessels during June to October 2006 to 2018. Typically, MODIS AOD w</span><span style="font-family:Verdana;">as</span><span style="font-family:Verdana;"> higher at low and lower at high values than the AERONET AOD. Discrepancies were largest for sites where the Earth’s surface around the site is very heterogeneous (Canadian Archipelago, coast of Greenland). Due to the higher likelihood for sea-ice, MAN and MODIS AOD differed stronger west of Greenland and over the Beaufort Sea than at location in the Greenland and Norwegian Seas and Atlantic. MODIS AOD well captured the inter-seasonal variability found in the AERONET AOD data (R = 0.933). At all sites, MO</span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">DIS and AERONET AOD agreement improved as time progressed in the shipping season, hinting at errors in sea-ice vs. open water classification. Overall 75.3% of the MODIS AOD data fell within the limits of the error envelops of the AERONET/MAN AOD data with MAN ranging between 87.5% and 100%. Changes in both MODIS and AERONET mean AOD between two periods of same length (2006-2011, 2013-2018) were explainable by changes in emissions for all sites</span><span style="font-family:Verdana;">.</span>
基金supported by the National Natural Science Foundations of China (Nos.41475136 and 41590871)International Science & Technology Cooperation Program of China (No.2013DFG22820)
文摘This study presents detailed analysis of spatiotemporal variations and trend of dust optical properties i.e., Aerosol Optical Depth(AOD) and Angstrom component over Asian desert regions using thirteen years of data(i.e., 2001–2013) retrieved from Aerosol Robotic Network(AERONET), Moderate Resolution Imaging Spectroradiometer(MODIS) and Multi-angle Imaging Spectroradiometer(MISR). These regions include Solar Village, Dunhuang and Dalangzadgad and are considered as origin of desert aerosols in Asia. Mann–Kendall trend test was used to show the trend of AOD. The relationship of AOD with weather parameters and general AOD trend over different wavelengths has also been shown. AOD's trend has been observed significant throughout the year in Solar Village, while in Dunhuang and Dalanzadgad the significant trend has been found only in peak period(March–June).Analysis show high values of AOD and low values of angstrom in Solar Village during peak period. In Chinese desert regions, high values of AOD have been found during peak period and low values in pre-peak period. Significant relationship has been observed between AOD and average temperature in Solar Village and Dalanzadgad whereas rainfall and wind speed showed no significant impact on AOD in all desert regions.
基金This research is supported by a China-France PRA project, the National Science Foundation of China （40250120071）the Chinese Academy of Sciences （2003-2-9）
文摘Aerosol Optical Thickness （AOT）, water vapor content and derived Angstrom exponent acquired by a CIMEL sun photometer in Beijing are analyzed. Monthly means computed from quality-assured daily means, seasonal trends and inter-annual variations are presented and discussed. Summer has the highest seasonal average AOT at 440 nm （τa440）, Angstrom exponent （α440-870） and water vapor content with the values 0.93, 1.34 and 3.0 cm, respectively. The second highest seasonal average τa440 appears in spring with the largest variation of α440-870 and minimum α440-870 0.99 due to the impact of coarse particles. The minimum seasonal average τa440 （0.44） and water vapor content （0.4 cm） appear in winter. The annual average τa440 , α440-870 and water vapor content for about 4-year observation period are 0.70, 1.19 and 1.4 cm, respectively. All monthly average Angstrom exponents are within 0.8-1.4. which indicates aerosol in Beijing is a very complex mixture of both fine- and coarse-mode particles （from anthropogenic influence and natural mineral dust）.
