The optical and microphysical properties of aerosols remain one of the greatest uncertainties associated with evaluating the climate forcing attributed to aerosols.Although the trends in aerosol optical depth(AOD)at g...The optical and microphysical properties of aerosols remain one of the greatest uncertainties associated with evaluating the climate forcing attributed to aerosols.Although the trends in aerosol optical depth(AOD)at global and regional scales have been widely examined,little attention has been paid to the trends in type-dependent AODs related to aerosol particle properties.Here,using the aerosol optical component dataset from the Multi-angle Imaging SpectroRadiometer(MISR)instrument,we investigate decadal-scale trends in total aerosol loading as well as AODs for five aerosol components by particle size and morphology during 2003–2018 over land.Relationships between the total AOD(TAOD)trends and type-dependent AOD changes were examined,and the relative contribution of each type-dependent AOD to the overall TAOD trends was quantified.By dividing the TAOD values into four different aerosol pollution levels(APLs)with splits at 0.15,0.40,and 0.80,we further explored the relationships between TAOD changes and interannual variations in the frequency-of-occurrences(FoOs)of these APLs.Long-term trends in FoOs in the different APLs show that there was a significant improvement in air quality between 2003 and 2018 in most land areas,except South Asia,corresponding to a shift from lightly polluted to clean conditions.However,the effects of different APLs on TAOD changes are regionally dependent and their extent of correlation varied spatially.Moreover,we observed that the annual mean TAOD has decreased by 0.47%.a^(-1)over land since 2003(P<0.05).This significant reduction was mainly attributed to the continued reduction in small-sized(<0.7 mm diameter)AOD(SAOD)(-0.74%.a^(-1))and spherical AOD(SPAOD)(-0.46%.a^(-1)).Statistical analysis shows that SAOD and SPAOD respectively accounted for 57.5%and 89.6%of the TAOD,but contributed 82.6%and 90.4%of the trend in TAOD.Our study suggests that small-sized and spherical aerosols composed of sulfate,organic matter,and black carbon play a dominant role in determining interannual variability in land TAOD.展开更多
The morphology and properties of corn starch and cassava starch were compared by SEM, DSC and TGA. Theeffects of amylose and amylopectin content on starch properties were studied by FT-IR, XRD and XPS. The plywood wa...The morphology and properties of corn starch and cassava starch were compared by SEM, DSC and TGA. Theeffects of amylose and amylopectin content on starch properties were studied by FT-IR, XRD and XPS. The plywood was pressed with the prepared adhesive and the bonding strength of the plywood was tested to analyze thedifference among the adhesives from different plant sources and the difference after blending PAPI prepolymer.FT-IR results showed that the hydroxyl peak of cassava starch was stronger and wider. TGA showed that the residue of cassava starch was lower, but the thermal stability of cassava starch was almost the same. XPS data showedthat the oxygen content of cassava starch was slightly higher, but the carbon content was slightly lower. SEM analysis showed that corn starch granules were more irregular and sharper than cassava starch, and cassava starchgranules were more uniform, regular and round.展开更多
作为21世纪乃至近30年最强的火山喷发之一,2022年汤加火山喷发事件已经引起了广泛关注.研究表明,汤加火山喷发所产生的大量火山灰气溶胶突破对流层进入平流层,形成了一个顶部高度约为25~30 km的火山灰羽流.在喷发后的4天内,火山灰羽流...作为21世纪乃至近30年最强的火山喷发之一,2022年汤加火山喷发事件已经引起了广泛关注.研究表明,汤加火山喷发所产生的大量火山灰气溶胶突破对流层进入平流层,形成了一个顶部高度约为25~30 km的火山灰羽流.在喷发后的4天内,火山灰羽流在平流层环流的驱动下迅速向西移动了近10000 km.侵入平流层的火山灰气溶胶导致整个澳大利亚北部的大气气溶胶负荷显著增加,气溶胶光学厚度(AOD)在澳大利亚东北部海岸达到1.5,约为侵入前一日的15倍.此次汤加火山灰羽流主要以半径集中在~0.26μm处的细模态颗粒物为主,同时其体积峰值达到0.25μm^(3)μm^(-2).汤加火山喷发对平流层AOD和辐射平衡的影响显著,卫星观测到的平流层AOD的扰动高达0.6.这种扰动在很大程度上解释了区域性地表(大气层顶)的瞬时短波辐射强迫可达-105.0 W m^(-2)(-65.0 W m^(-2)).展开更多
基金supported by the National Key Research and Development Program Pilot Projects of China(2016YFA0601901)the National Science Fund for Distinguished Young Scholars(41825011)the National Natural Science Foundation of China(42030608,41590874,and 41941011)。
文摘The optical and microphysical properties of aerosols remain one of the greatest uncertainties associated with evaluating the climate forcing attributed to aerosols.Although the trends in aerosol optical depth(AOD)at global and regional scales have been widely examined,little attention has been paid to the trends in type-dependent AODs related to aerosol particle properties.Here,using the aerosol optical component dataset from the Multi-angle Imaging SpectroRadiometer(MISR)instrument,we investigate decadal-scale trends in total aerosol loading as well as AODs for five aerosol components by particle size and morphology during 2003–2018 over land.Relationships between the total AOD(TAOD)trends and type-dependent AOD changes were examined,and the relative contribution of each type-dependent AOD to the overall TAOD trends was quantified.By dividing the TAOD values into four different aerosol pollution levels(APLs)with splits at 0.15,0.40,and 0.80,we further explored the relationships between TAOD changes and interannual variations in the frequency-of-occurrences(FoOs)of these APLs.Long-term trends in FoOs in the different APLs show that there was a significant improvement in air quality between 2003 and 2018 in most land areas,except South Asia,corresponding to a shift from lightly polluted to clean conditions.However,the effects of different APLs on TAOD changes are regionally dependent and their extent of correlation varied spatially.Moreover,we observed that the annual mean TAOD has decreased by 0.47%.a^(-1)over land since 2003(P<0.05).This significant reduction was mainly attributed to the continued reduction in small-sized(<0.7 mm diameter)AOD(SAOD)(-0.74%.a^(-1))and spherical AOD(SPAOD)(-0.46%.a^(-1)).Statistical analysis shows that SAOD and SPAOD respectively accounted for 57.5%and 89.6%of the TAOD,but contributed 82.6%and 90.4%of the trend in TAOD.Our study suggests that small-sized and spherical aerosols composed of sulfate,organic matter,and black carbon play a dominant role in determining interannual variability in land TAOD.
基金This work was supported by the National Natural Science Foundation of China(No.31670569)the Fundamental Research Funds for the Central Universities(No.2572019CG05)Special thanks to the support of the Chinese University Students,Innovation and Entrepreneurship Project(202010225071).
文摘The morphology and properties of corn starch and cassava starch were compared by SEM, DSC and TGA. Theeffects of amylose and amylopectin content on starch properties were studied by FT-IR, XRD and XPS. The plywood was pressed with the prepared adhesive and the bonding strength of the plywood was tested to analyze thedifference among the adhesives from different plant sources and the difference after blending PAPI prepolymer.FT-IR results showed that the hydroxyl peak of cassava starch was stronger and wider. TGA showed that the residue of cassava starch was lower, but the thermal stability of cassava starch was almost the same. XPS data showedthat the oxygen content of cassava starch was slightly higher, but the carbon content was slightly lower. SEM analysis showed that corn starch granules were more irregular and sharper than cassava starch, and cassava starchgranules were more uniform, regular and round.
基金supported by the National Science Fund for Distinguished Young Scholars(41825011)the National Natural Science Foundation of China(42175153 and 42030608)the Basic Research Fund of Chinese Academy of Meteorological Sciences(2021Y001)。
文摘作为21世纪乃至近30年最强的火山喷发之一,2022年汤加火山喷发事件已经引起了广泛关注.研究表明,汤加火山喷发所产生的大量火山灰气溶胶突破对流层进入平流层,形成了一个顶部高度约为25~30 km的火山灰羽流.在喷发后的4天内,火山灰羽流在平流层环流的驱动下迅速向西移动了近10000 km.侵入平流层的火山灰气溶胶导致整个澳大利亚北部的大气气溶胶负荷显著增加,气溶胶光学厚度(AOD)在澳大利亚东北部海岸达到1.5,约为侵入前一日的15倍.此次汤加火山灰羽流主要以半径集中在~0.26μm处的细模态颗粒物为主,同时其体积峰值达到0.25μm^(3)μm^(-2).汤加火山喷发对平流层AOD和辐射平衡的影响显著,卫星观测到的平流层AOD的扰动高达0.6.这种扰动在很大程度上解释了区域性地表(大气层顶)的瞬时短波辐射强迫可达-105.0 W m^(-2)(-65.0 W m^(-2)).
