| Aerosols play an important role in global climate change and terrestrial ecosystem.Aerosols can disturbing the energy budget of the earth-atmosphere system through direct and indirect effects,and then affect the distribution of terrestrial ecosystem productivity.In recent years,with the rapid development of economy and the rapid growth of anthropogenic emissions,more and more attention has been paid to the climate effects of anthropogenic aerosols and their impact on terrestrial ecosystems.In order to scientifically understand and evaluate the impact of anthropogenic aerosols on global climate and terrestrial ecosystem,this paper analyzes the optical properties of aerosols based on MODIS and MERRA-2 data.On this basis,this paper takes anthropogenic aerosols as the research object,with numerical simulation as the main research method.The direct and total radiative effects of anthropogenic aerosols were simulated by CESM.The direct radiative effects of two dominant aerosols（sulfate aerosol and carbonaceous aerosol）in anthropogenic aerosols were quantitatively studied,and the effects of total radiative effects of these two aerosols on temperature,precipitation and terrestrial ecosystem were also studied.The main work and conclusions of this study are as follows:1.Using MODIS and MERRA-2 data to analyze aerosol optical properties from 2001 to 2019,the results show that:（1）According to the temporal and spatial distribution of AOD,the high value areas of AOD are in the Amazon River Basin,the Sahara desert in North Africa,the Congo Basin,the Arabian Peninsula,the south side of Himalayas in India,and the North Plain,Tarim Basin,Sichuan Basin in China and Malay islands.The total AOD show a downward trend from 2001 to 2019.Black carbon aerosols are mainly distributed in Amazon rainforest,Congo rainforest,Indian peninsula,Eastern China and Malay islands,and the AOD of black carbon aerosols show an upward trend from 2001 to2019;organic carbon aerosols are mainly distributed in Amazon rainforest,Congo rainforest and Malay islands,and the AOD of organic carbon aerosols show an upward trend from 2001 to 2019;sulfate aerosols are mainly distributed in eastern China from2001 to 2019,and the AOD of sulfate aerosols show a downward trend;（2）According to the temporal and spatial distribution of aerosols Angstrom wavelength index,coarse-grained aerosols are dominant in the Sahara desert,Arabian Peninsula and Tarim Basin,fine-grained aerosols are dominant in South America,southern Africa and Malay islands,while the dominant aerosols in eastern China and Indian peninsula have no obvious characteristics of particle size distribution.From2001 to 2019,the wavelength index of aerosol is on the rise,while the AOD is on the decline,so the coarse size aerosol decreases during this period.（3）According to the aerosol single scattering albedo,combined with the aerosol optical thickness and the spatial-temporal distribution of Angstrom wavelength index,the value of single scattering albedo in the high value area of dust aerosol is smaller,so the absorption capacity of dust aerosol is stronger than the scattering capacity;the value of single scattering albedo in the high value area of sulfate aerosol is larger,so the scattering energy of sulfate aerosol can be obtained It’s strong.From 2001 to 2019,the single scattering albedo shows a downward trend,so the contribution of aerosol scattering to extinction decreased faster than that of absorption during this period.2.The direct radiative effects of total aerosols and two kinds of aerosols dominated by human activities（sulfate aerosols and carbonaceous aerosols）on the top of the atmosphere and the surface are simulated by CESM:（1）The direct radiative forcing at the top of the atmosphere is-1.37W/m2（-0.73%）、-0.46 W/m2（-0.25%）、-0.45 W/m2（-0.24%）under clear sky conditions,and-0.30W/m2（-0.19%）、-0.25 W/m2（-0.16%）、+0.04 W/m2（+0.03%）under cloudy conditions.The existence of cloud can enhance the positive effect of aerosols at the top of atmosphere,and weaken the negative effect at the top of atmosphere;（2）The direct radiative forcing on the surface is-5.60 W/m2（-4.22%）、-0.53 W/m2（-0.40%）、-2.21 W/m2（-1.67%）under clear sky conditions,and-4.38 W/m2（-4.38%）、-0.32 W/m2（-0.32%）、-1.64 W/m2（-1.64%）under cloudy conditions.The existence of cloud can weaken the surface radiation effect of aerosols.3.The total radiative effects of anthropogenic aerosols,sulfate aerosols and carbonaceous aerosols on temperature and precipitation are simulated by CESM:（1）The indirect effects of total anthropogenic aerosols,sulfate aerosols and carbonaceous aerosols increase the cloud droplet number concentration by 0.029×105#/cm2、0.017×105#/cm2、0.001×105#/cm2 respectively;the total anthropogenic aerosols and sulfate aerosols increase the cloud cover by 0.279%and 0.405%respectively,while the carbonaceous aerosols decrease the cloud cover by 0.078%.Total anthropogenic aerosols and sulfate aerosols reduced precipitation by 0.066mm/d and 0.052 mm/d,respectively,while carbon aerosols increased by 0.005 mm/d;（2）Total anthropogenic aerosols and sulfate aerosols reduce the global surface temperature by 0.744K and 0.619K respectively,while carbon aerosols weaken the effect of clouds on solar radiation by reduce the cloud cover,and increases the global surface temperature by 0.201K on average.4.Based on CESM simulation,the effects of total anthropogenic aerosol,sulfate aerosol and carbonaceous aerosol on terrestrial ecosystem were studied:（1）Total anthropogenic aerosol and sulfate aerosol cooled the soil by weakening the solar radiation,thus inhibiting vegetation transpiration,maintaining high soil humidity,and increasing soil humidity by 0.83×10-3mm3/mm3 and 0.07×10-3mm3/mm3 respectively;the decrease of cloud volume caused by carbon aerosols leads to the increase of solar radiation to the surface,the increase of soil temperature enhances vegetation transpiration,and reduces soil humidity,with an average decrease of 0.10×10-3mm3/mm3;（2）Total anthropogenic aerosols,sulfate aerosols and carbonaceous aerosols reduced GPP by 24.71g C·m-2·a-1（-4.53%）、17.13g C·m-2·a-1（-3.14%）、1.61g C·m-2·a-1（-0.29%）,respectively.The spatial distribution of total anthropogenic aerosol and sulfate aerosol is basically the same,and the GPP decreased in most regions except northern India,central South America and Australia.However,carbon aerosols significantly increased GPP in Amazon rainforest,Congo rainforest and Malay islands,especially in Congo rainforest,which increased by 57.73g C·m-2·a-1 per unit area;（3）The direct weakening of solar radiation by anthropogenic aerosols reduce the carbon sequestration of sunny leaves,while the scattering of solar radiation increases the carbon sequestration of shady leaves.The total anthropogenic aerosols resulted in a decrease of 2.77%in the carbon sequestration of sunny leaves,and an increase of 1.50%in the carbon sequestration of shady leaves,which made up for the decrease of 54.1%in the carbon sequestration of sunny leaves.Sulfate aerosols resulted in a 2.27%decrease in the carbon sequestration of positive leaves,while a 1.73%increase in the carbon sequestration of negative leaves,which made up for the 76.2%decrease in the carbon sequestration of positive leaves.The carbon aerosols resulted in a 0.66%decrease in the carbon sequestration of sunny leaves and a 0.53%increase in the carbon sequestration of shady leaves.The change of carbon sequestration in both sunny and shady leaves was not significant.This is because the carbon aerosols weaken the intensity of the total photosynthetically active radiation and weakens the scattered radiation,which leads to the phenomenon that the carbon sequestration of the sunny leaves decrease less and the carbon sequestration of the shady leaves increase less obviously. |
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