Global aerosol optical thickness (AOT) data over land obtained from the Moderate Resolu-tion Imaging Spectroradiometer (MODIS) are evaluated through comparisons with AOT data retrieved by Aerosol Robotic Network (AERO...Global aerosol optical thickness (AOT) data over land obtained from the Moderate Resolu-tion Imaging Spectroradiometer (MODIS) are evaluated through comparisons with AOT data retrieved by Aerosol Robotic Network (AERONET). In general, MODIS overestimates AOT except at a few AERONET sites in Africa and eastern Asia. MODIS/AOTs are, on average, larger than AERONET/AOTs by 0.041 and 0.090 at 470 nm and 660 nm, respectively. The AOT bias at 660 nm is significantly correlated to the surface reflectance at 2130 nm. Both facts suggest that the underestimation of the surface reflectance is the principal reason for this bias at 660 nm. To use the MODIS/AOT at 470 nm is strongly recommended because it is much more reliable than the AOT at 660 nm.展开更多
Ozonesondes are widely used to obtain ozone concentration profiles from the surface to the upper atmosphere.A kind of double-cell ozonesonde has been developed at the Institute of Atmospheric Physics （IAP）,Chinese A...Ozonesondes are widely used to obtain ozone concentration profiles from the surface to the upper atmosphere.A kind of double-cell ozonesonde has been developed at the Institute of Atmospheric Physics （IAP）,Chinese Academy of Sciences （named the ＂IAP ozonesonde＂） based on previous experience over the past 20 years of developing the singlecell GPSO3 ozonesonde.The IAP ozonesonde is of the Electrochemical Concentration Cell （ECC） type.A detailed description of the IAP ozonesonde is firstly provided in the present paper,followed by a presentation of results from a series of launches carried out to evaluate its performance.The analysis involved comparing its observations with measurements from the GPSO3 and ECC ozonesondes （Model type ENSCI-Z） as well as a Brewer spectrophotometer.The results showed that the IAP ozonesonde is a vast improvement over the GPSO3 ozonesonde,able to capture vertical ozone structures very well and in good agreement with ECC ozonesonde measurements.The average difference in the ozone partial pressure between the IAP and ECC ozonesondes was 0.3 mPa from the surface to 2.5 km,close to zero from 2.5 to 9 km and generally less than 1 mPa for layers higher than 9 km.The apparent deviation is likely caused by a decreasing pump flow rate in the IAP ozonesonde which needs further improvement.The total ozone amounts measured by the IAP ozonesonde profiles were highly comparable with the Brewer data with a relative difference of 6％.The development of the IAP ozonesonde and its strong performance will surely accelerate the process of conventional observations of ozone profiles over China in the near future as well as provide more data for ozone research in general.展开更多
Characterization of aerosols is required to reduce uncertainties in satellite retrievals of global aerosols and for modeling the effects of these aerosols on climate.Aerosols in the North China Plain(NCP) are complex,...Characterization of aerosols is required to reduce uncertainties in satellite retrievals of global aerosols and for modeling the effects of these aerosols on climate.Aerosols in the North China Plain(NCP) are complex,which provides a good opportunity to study key aerosol optical properties for various aerosol types.A cluster analysis of key optical properties obtained from Aerosol Robotic Network(AERONET) data in Beijing and Xianghe during 2001-11 was performed to identify dominant aerosol types and their associated optical properties.Five dominant aerosol types were identified.The results show that the urban/industrial aerosol of moderate absorption was dominant in the region and that this type varied little with season.Urban/industrial aerosol of weak absorption was the next most common type and mainly occurs in summer,followed by that strong aerosols occurring mainly in winter.All were predominantly fine mode particles.Mineral dust(MD) and polluted dust(PD) occurred mainly in spring,followed by winter,and their absorption decreased with wavelength.In addition,aerosol dynamics and optical parameters such as refractive index and asymmetry factor were examined.Results show that the size of coarse mode particles decreased with AOD indicating the domination of external mixing between aerosols.展开更多
To make a detailed test on the reliability and detection performance of the electrochemical concentra- tion cell （ECC） type ozonesonde which had been devel- oped and preliminarily evaluated by the authors, an inten-...To make a detailed test on the reliability and detection performance of the electrochemical concentra- tion cell （ECC） type ozonesonde which had been devel- oped and preliminarily evaluated by the authors, an inten- sive ozonesonde release experiment was held at two sites in Beijing and Changchun in June 2013. The results showed that the mean background current and its standard deviation were 0.03 （0.04） pA and 0.02 （0.03） pA in Bei- jing （Changchun）. The average response time and its standard deviation were 27.8 s （30.4 s） and 4.0 s （3.7 s） in Beijing （Changchun）. The ozone partial pressure profiles at both sites showed a central peak in the stratosphere and a side peak in the boundary layer. Large variation in ozone partial pressure was observed at the middle levels of the atmosphere （10-17 kin）. A more marked gradient of ozone change was observed in Beijing （3.4 mPa km-1） at the lower atmosphere level, as compared to that in Changchun （0.4 mPa km-l）. The results presented in this paper indicate that this self-developed ozonesonde shows a high level of reliability and good performance. The ozonsonde is expected to play an important role in opera- tional observations of ozone profiles.展开更多
The aerosol effect on clouds was explored using remote sensing of aerosol and cloud data at Shouxian, China. Non-precipitation, ice-free, and overcast clouds were firstly chosen by a combination of sky im- ages from t...The aerosol effect on clouds was explored using remote sensing of aerosol and cloud data at Shouxian, China. Non-precipitation, ice-free, and overcast clouds were firstly chosen by a combination of sky im- ages from the Total Sky Imager （TSI）, cloud base heights from the Ceilometer, and vertical temperature profiles from the Balloon-Borne Sounding System （BBSS）. Six cases were chosen in summer, and seven in autumn. The averaged cloud effective radii （re）, cloud optical depth （COD）, aerosol total light scattering coefficient （a）, and liquid water path （LWP） are, respectivey, 6.47 μm, 35.4, 595.9 mm-1, 0.19 mm in summer, and 6.07 μm, 96.0, 471.7 mm-1, 0.37 mm in autumn. The correlation coefficient between re and tc was found to change from negative to positive value as LWP increases.展开更多
The column-integrated optical properties of aerosol in Beijing and Xianghe, two AErosol RObotic NETwork（AERONET）sites situated on the North China Plain（NCP）, are investigated based on Cimel sunphotometer measureme...The column-integrated optical properties of aerosol in Beijing and Xianghe, two AErosol RObotic NETwork（AERONET）sites situated on the North China Plain（NCP）, are investigated based on Cimel sunphotometer measurements from October2004 to June 2012. The outstanding feature found is that the seasonal medians of aerosol optical depth（AOD） at the two stations are in good agreement. The correlation coefficients and the absolute differences between AOD at the two stations are larger than 0.84 and less than 0.05, respectively. Good agreement in AOD at these two sites（one urban and the other suburban; 70 km apart） indicates that aerosol pollution in the Greater Beijing area is regional in nature. However, we find significant differences in the absorption ？Angstr ¨om Exponent（AAE）, the real and imaginary part of the refractive index, and thereby the single scattering albedo（SSA）, and the difference is seasonally dependent. The feature is found to be more prominent in fall when the fine-mode fraction（FMF） and fine-mode effective radius are significantly different at the two stations,besides the parameters mentioned above. The SSA in Beijing at four wavelengths shows lower values as compared to those in Xianghe, although the difference is not significant in some cases. Significant differences in AAE and fine-mode effective radius indicate that there are differences in aerosol physical and chemical properties in urban and suburban regions on the NCP.展开更多
Total Cloud Cover （TCC） over China deter- mined from four climate datasets including the Interna- tional Satellite Cloud Climatology Project （ISCCP）, the 40-year Re-Analysis Project of the European Centre for Medi...Total Cloud Cover （TCC） over China deter- mined from four climate datasets including the Interna- tional Satellite Cloud Climatology Project （ISCCP）, the 40-year Re-Analysis Project of the European Centre for Medium-Range Weather Forecasts （ERA-40）, Climate Research Unit Time Series 3.0 （CRU3）, and ground sta- tion datasets are used to show spatial and temporal varia- tion of TCC and their differences. It is demonstrated that the four datasets show similar spatial pattern and seasonal variation. The maximum value is derived from ISCCE TCC value in North China derived from ERA-40 is 50% larger than that from the station dataset; however, the value is 50% less than that in South China. The annual TCC of ISCCP, ERA-40, and ground station datasets shows a decreasing trend during 1984-2002; however, an increasing trend is derived from CRU3. The results of this study imply remarkable differences of TCC derived from surface and satellite observations as well as model simu- lations. The potential effects of these differences on cloud climatology and associated climatic issues should be carefully considered.展开更多
The properties of summer radiation and aerosols were studied at Xinzhou,a suburban site on the North China Plain(NCP)by using ground-based measurements in 2014.The radiation detections under clear and cloudy skies sho...The properties of summer radiation and aerosols were studied at Xinzhou,a suburban site on the North China Plain(NCP)by using ground-based measurements in 2014.The radiation detections under clear and cloudy skies showed that longwave radiation presented a sigmate pattern,with a maximum of 392.6 W m-2at 1700 local standard time(LST)associated with the cloud radiative forcing,and a minimum of 360.0 W m-2at 0600 LST when the lowest surface temperature(17.1°C)occurred.Solar radiation,including global,direct,diffuse,photosynthetically active,ultraviolet-A,and ultraviolet-B,exhibited a single peak at^1300 LST.A bimodal size distribution,with fine mode aerosols showing a peak between 0.1 and 0.2μm and coarse mode aerosols showing a peak at^5μm,was observed at Xinzhou.The dominant aerosol type was black carbon coating on coarse particles(85.7%)for the cases with aerosol optical depth at 400 nm(AOD)greater than 0.4,leading to a lower single scattering albedo(0.81)than the typical value(~0.90)at the other stations on the NCP.The mean values of EAE and AAE(extinction and absorption?ngstr?m exponent,respectively)were 1.14±0.15 and 0.58±0.28 for the aerosol measurements.The average of instantaneous aerosol direct radiative forcing at the bottom of the atmosphere was-138.9±33.0 W m-2for the cases with AOD>0.4.The results in this study are expected to improve understanding at suburban sites on the NCP of aerosol properties and their impacts on regional radiation budgets.展开更多
Variability and long-term trends of sunshine duration(SSD) and total cloud cover(TCC) were studied based on surface observations from 10 meteorological stations over East China in the first half of the 20 th century. ...Variability and long-term trends of sunshine duration(SSD) and total cloud cover(TCC) were studied based on surface observations from 10 meteorological stations over East China in the first half of the 20 th century. The correlation coefficients between SSD and diurnal temperature range(DTR), as well as TCC, were analyzed. SSD experienced a significant increasing trend(0.16 h d-1 per decade) from 1908 to 1936, and the maximum brightening was in autumn(0.33 h d-1 per decade). The good agreement between the variability of SSD and DTR, supported by the correlation coefficient between them of 0.72, implies that the SSD measurements were reliable. TCC showed a decreasing trend(-0.93% per decade) and was significantly inversely related to SSD(-0.74), indicating the variation of SSD was attributable to changes in cloud cover. The result was obviously different to that since the 1960 s, when clouds could not account for the decadal trend of surface solar radiation in China.展开更多
本文根据不同类型云影响地面短波辐射的差异,提出利用地面短波总辐射变化检测识别淡积云以及计算淡积云水平尺度的方法,并对该算法进行误差分析,统计内蒙古草原地区夏季淡积云的水平尺度及其辐射强迫。结果表明:淡积云检测方法能比较好...本文根据不同类型云影响地面短波辐射的差异,提出利用地面短波总辐射变化检测识别淡积云以及计算淡积云水平尺度的方法,并对该算法进行误差分析,统计内蒙古草原地区夏季淡积云的水平尺度及其辐射强迫。结果表明:淡积云检测方法能比较好地识别、筛选出淡积云天。淡积云水平尺度和淡积云所在高度的风速成正比,风速测量的准确性直接影响淡积云水平尺度估算准确性;淡积云水平与垂直尺度比对计算淡积云水平尺度影响最大;云移动经过遮挡太阳直射辐射的时段内,太阳天顶角变化的影响可以忽略不计。内蒙古草原地区夏季淡积云短波辐射强迫小时平均为-134.1 W m-2,水平尺度平均值为1129 m,水平尺度的概率密度呈幂指数分布。展开更多
基金The research is supported by the National Natural Science Foundation of China(Grant Nos.40305002,40333029 and 40520120071).
文摘Global aerosol optical thickness (AOT) data over land obtained from the Moderate Resolu-tion Imaging Spectroradiometer (MODIS) are evaluated through comparisons with AOT data retrieved by Aerosol Robotic Network (AERONET). In general, MODIS overestimates AOT except at a few AERONET sites in Africa and eastern Asia. MODIS/AOTs are, on average, larger than AERONET/AOTs by 0.041 and 0.090 at 470 nm and 660 nm, respectively. The AOT bias at 660 nm is significantly correlated to the surface reflectance at 2130 nm. Both facts suggest that the underestimation of the surface reflectance is the principal reason for this bias at 660 nm. To use the MODIS/AOT at 470 nm is strongly recommended because it is much more reliable than the AOT at 660 nm.
基金supported by the Special Fund for Public Welfare Industry (Meteorology) under Grant No. GYHY201106041the Strategic Priority Research Program (B) of the Chinese Academy of Sciences under Grant No. XDB05020503
文摘Ozonesondes are widely used to obtain ozone concentration profiles from the surface to the upper atmosphere.A kind of double-cell ozonesonde has been developed at the Institute of Atmospheric Physics （IAP）,Chinese Academy of Sciences （named the ＂IAP ozonesonde＂） based on previous experience over the past 20 years of developing the singlecell GPSO3 ozonesonde.The IAP ozonesonde is of the Electrochemical Concentration Cell （ECC） type.A detailed description of the IAP ozonesonde is firstly provided in the present paper,followed by a presentation of results from a series of launches carried out to evaluate its performance.The analysis involved comparing its observations with measurements from the GPSO3 and ECC ozonesondes （Model type ENSCI-Z） as well as a Brewer spectrophotometer.The results showed that the IAP ozonesonde is a vast improvement over the GPSO3 ozonesonde,able to capture vertical ozone structures very well and in good agreement with ECC ozonesonde measurements.The average difference in the ozone partial pressure between the IAP and ECC ozonesondes was 0.3 mPa from the surface to 2.5 km,close to zero from 2.5 to 9 km and generally less than 1 mPa for layers higher than 9 km.The apparent deviation is likely caused by a decreasing pump flow rate in the IAP ozonesonde which needs further improvement.The total ozone amounts measured by the IAP ozonesonde profiles were highly comparable with the Brewer data with a relative difference of 6％.The development of the IAP ozonesonde and its strong performance will surely accelerate the process of conventional observations of ozone profiles over China in the near future as well as provide more data for ozone research in general.
基金supported by the National Key R&D Program of China[grant number 2022YFF0801301]the National Natural Science Foundation of China[grant number 41575033]+1 种基金the Fengyun Satellite Application Pioneer Project[grant number FY-APP-2022.0111]the Natural Science Foundation of Jiangsu Province[grant number BK20231148]。
基金supported by the National Basic Research Program of China (2013CB955801)the National Natural Science Foundation of China (41175031)the "Strategic Priority Research Program" of the Chinese Academy of Sciences (XDA05100300)
文摘Characterization of aerosols is required to reduce uncertainties in satellite retrievals of global aerosols and for modeling the effects of these aerosols on climate.Aerosols in the North China Plain(NCP) are complex,which provides a good opportunity to study key aerosol optical properties for various aerosol types.A cluster analysis of key optical properties obtained from Aerosol Robotic Network(AERONET) data in Beijing and Xianghe during 2001-11 was performed to identify dominant aerosol types and their associated optical properties.Five dominant aerosol types were identified.The results show that the urban/industrial aerosol of moderate absorption was dominant in the region and that this type varied little with season.Urban/industrial aerosol of weak absorption was the next most common type and mainly occurs in summer,followed by that strong aerosols occurring mainly in winter.All were predominantly fine mode particles.Mineral dust(MD) and polluted dust(PD) occurred mainly in spring,followed by winter,and their absorption decreased with wavelength.In addition,aerosol dynamics and optical parameters such as refractive index and asymmetry factor were examined.Results show that the size of coarse mode particles decreased with AOD indicating the domination of external mixing between aerosols.
基金supported by the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant No.XDB05020503)the Special Fund for Public Welfare Industry (Meteorology) (Grant No.GYHY201106041)
文摘To make a detailed test on the reliability and detection performance of the electrochemical concentra- tion cell （ECC） type ozonesonde which had been devel- oped and preliminarily evaluated by the authors, an inten- sive ozonesonde release experiment was held at two sites in Beijing and Changchun in June 2013. The results showed that the mean background current and its standard deviation were 0.03 （0.04） pA and 0.02 （0.03） pA in Bei- jing （Changchun）. The average response time and its standard deviation were 27.8 s （30.4 s） and 4.0 s （3.7 s） in Beijing （Changchun）. The ozone partial pressure profiles at both sites showed a central peak in the stratosphere and a side peak in the boundary layer. Large variation in ozone partial pressure was observed at the middle levels of the atmosphere （10-17 kin）. A more marked gradient of ozone change was observed in Beijing （3.4 mPa km-1） at the lower atmosphere level, as compared to that in Changchun （0.4 mPa km-l）. The results presented in this paper indicate that this self-developed ozonesonde shows a high level of reliability and good performance. The ozonsonde is expected to play an important role in opera- tional observations of ozone profiles.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(KZCX2-YW-QN201)the National Basic Research Program of China(973 Program)(2006CB403706 and 2010CB950804)the National Natural Science Foundation of China(40775009 and 40875084)
文摘The aerosol effect on clouds was explored using remote sensing of aerosol and cloud data at Shouxian, China. Non-precipitation, ice-free, and overcast clouds were firstly chosen by a combination of sky im- ages from the Total Sky Imager （TSI）, cloud base heights from the Ceilometer, and vertical temperature profiles from the Balloon-Borne Sounding System （BBSS）. Six cases were chosen in summer, and seven in autumn. The averaged cloud effective radii （re）, cloud optical depth （COD）, aerosol total light scattering coefficient （a）, and liquid water path （LWP） are, respectivey, 6.47 μm, 35.4, 595.9 mm-1, 0.19 mm in summer, and 6.07 μm, 96.0, 471.7 mm-1, 0.37 mm in autumn. The correlation coefficient between re and tc was found to change from negative to positive value as LWP increases.
基金supported by the National Basic Research Program of China (Grant Nos. 2010CB950804 and 2013CB955801)National Natural Science Foundation of China (Grant No. 41475027)the Chinese Strategic Priority Research Program–Climate Change: Carbon Budget and Relevant Issues (Grant No. XDA05040202)
文摘The column-integrated optical properties of aerosol in Beijing and Xianghe, two AErosol RObotic NETwork（AERONET）sites situated on the North China Plain（NCP）, are investigated based on Cimel sunphotometer measurements from October2004 to June 2012. The outstanding feature found is that the seasonal medians of aerosol optical depth（AOD） at the two stations are in good agreement. The correlation coefficients and the absolute differences between AOD at the two stations are larger than 0.84 and less than 0.05, respectively. Good agreement in AOD at these two sites（one urban and the other suburban; 70 km apart） indicates that aerosol pollution in the Greater Beijing area is regional in nature. However, we find significant differences in the absorption ？Angstr ¨om Exponent（AAE）, the real and imaginary part of the refractive index, and thereby the single scattering albedo（SSA）, and the difference is seasonally dependent. The feature is found to be more prominent in fall when the fine-mode fraction（FMF） and fine-mode effective radius are significantly different at the two stations,besides the parameters mentioned above. The SSA in Beijing at four wavelengths shows lower values as compared to those in Xianghe, although the difference is not significant in some cases. Significant differences in AAE and fine-mode effective radius indicate that there are differences in aerosol physical and chemical properties in urban and suburban regions on the NCP.
基金supported by the "Strategic Priority Research Program" of the Chinese Academy of Sciences(XDA05100300)the National Basic Research Program of China(2013CB955801)the National Natural Science Foundation of China(41175030)
文摘Total Cloud Cover （TCC） over China deter- mined from four climate datasets including the Interna- tional Satellite Cloud Climatology Project （ISCCP）, the 40-year Re-Analysis Project of the European Centre for Medium-Range Weather Forecasts （ERA-40）, Climate Research Unit Time Series 3.0 （CRU3）, and ground sta- tion datasets are used to show spatial and temporal varia- tion of TCC and their differences. It is demonstrated that the four datasets show similar spatial pattern and seasonal variation. The maximum value is derived from ISCCE TCC value in North China derived from ERA-40 is 50% larger than that from the station dataset; however, the value is 50% less than that in South China. The annual TCC of ISCCP, ERA-40, and ground station datasets shows a decreasing trend during 1984-2002; however, an increasing trend is derived from CRU3. The results of this study imply remarkable differences of TCC derived from surface and satellite observations as well as model simu- lations. The potential effects of these differences on cloud climatology and associated climatic issues should be carefully considered.
基金supported by the National Key R&D Program of China grant number 2017YFA0603504the National Natural Science Foundation of China grant number 41875183。
文摘The properties of summer radiation and aerosols were studied at Xinzhou,a suburban site on the North China Plain(NCP)by using ground-based measurements in 2014.The radiation detections under clear and cloudy skies showed that longwave radiation presented a sigmate pattern,with a maximum of 392.6 W m-2at 1700 local standard time(LST)associated with the cloud radiative forcing,and a minimum of 360.0 W m-2at 0600 LST when the lowest surface temperature(17.1°C)occurred.Solar radiation,including global,direct,diffuse,photosynthetically active,ultraviolet-A,and ultraviolet-B,exhibited a single peak at^1300 LST.A bimodal size distribution,with fine mode aerosols showing a peak between 0.1 and 0.2μm and coarse mode aerosols showing a peak at^5μm,was observed at Xinzhou.The dominant aerosol type was black carbon coating on coarse particles(85.7%)for the cases with aerosol optical depth at 400 nm(AOD)greater than 0.4,leading to a lower single scattering albedo(0.81)than the typical value(~0.90)at the other stations on the NCP.The mean values of EAE and AAE(extinction and absorption?ngstr?m exponent,respectively)were 1.14±0.15 and 0.58±0.28 for the aerosol measurements.The average of instantaneous aerosol direct radiative forcing at the bottom of the atmosphere was-138.9±33.0 W m-2for the cases with AOD>0.4.The results in this study are expected to improve understanding at suburban sites on the NCP of aerosol properties and their impacts on regional radiation budgets.
基金supported by National Natural Science Foundation of China (41175031)
文摘Variability and long-term trends of sunshine duration(SSD) and total cloud cover(TCC) were studied based on surface observations from 10 meteorological stations over East China in the first half of the 20 th century. The correlation coefficients between SSD and diurnal temperature range(DTR), as well as TCC, were analyzed. SSD experienced a significant increasing trend(0.16 h d-1 per decade) from 1908 to 1936, and the maximum brightening was in autumn(0.33 h d-1 per decade). The good agreement between the variability of SSD and DTR, supported by the correlation coefficient between them of 0.72, implies that the SSD measurements were reliable. TCC showed a decreasing trend(-0.93% per decade) and was significantly inversely related to SSD(-0.74), indicating the variation of SSD was attributable to changes in cloud cover. The result was obviously different to that since the 1960 s, when clouds could not account for the decadal trend of surface solar radiation in China.
文摘本文根据不同类型云影响地面短波辐射的差异,提出利用地面短波总辐射变化检测识别淡积云以及计算淡积云水平尺度的方法,并对该算法进行误差分析,统计内蒙古草原地区夏季淡积云的水平尺度及其辐射强迫。结果表明:淡积云检测方法能比较好地识别、筛选出淡积云天。淡积云水平尺度和淡积云所在高度的风速成正比,风速测量的准确性直接影响淡积云水平尺度估算准确性;淡积云水平与垂直尺度比对计算淡积云水平尺度影响最大;云移动经过遮挡太阳直射辐射的时段内,太阳天顶角变化的影响可以忽略不计。内蒙古草原地区夏季淡积云短波辐射强迫小时平均为-134.1 W m-2,水平尺度平均值为1129 m,水平尺度的概率密度呈幂指数分布。
