Simulation Study Of Nitrate AOD And Effective Radiative Forcing

Many researches on sulfate aerosols had been done during the last two decades,which had contributed significantly to our understanding of the emission,concentration,optical properties and radiative forcing of sulfate in the atmosphere;whereas these kinds of study on nitrate was not given much attention before,since the concentration of nitrate aerosol in the atmosphere was much less than sulfate aerosol.Recent studies show that the scattering properties of nitrate are stronger than that of sulfate in some wave bands.Besides,the proportion of nitrate in total anthropogenic aerosols shows an increasing trend since the emissions of sulfate aerosol will be greatly reduced due to the controlling to its precursors at present and in the future,while the emissions of nitrate aerosol increase rapidly,and these changes will lead to higher radiative forcing caused by nitrate than that of sulfate.It is very likely that nitrate will become an important radiative forcing factor to affect climate change at regional and seasonal scales in the future.Therefore,in order to get some new insights into the concentration and radiative forcing of nitrate,this research have analyzed the distribution of emissions and simulated the concentration,AOD and radiative forcing of nitrate with the aerosol-climate coupled model BCC_AGCM_CUACE2.0 developed by the National Climate Center of the China Meteorological Administration(NCC/CMA).The main conclusions are as follows:(1)From the global scale,the loading of nitrate has increased 1.43 mg/m~2 from 1850 to 2010.And the increased nitrate loading was mainly distributed in East Asia,South Asia,Europe,and North America,especially in East Asia(the maximum is about 19.24 mg/m~2).In 2100,the loading of nitrate would increase by 0.45~1.04 mg/m~2 relative to 1850,and the increased nitrate loading would be mainly distributed in EA and EU.And the loading of nitrate increased obviously in winter.(2)The global mean AOD of nitrate has increased 0.005 from 1850 to 2010,and the increment would be 0.001~0.003 by 2100.The AOD of nitrate had a good correspondence with its loading.(3)Since 1850,the Radiative Forcing from aerosol–radiation interactions(RFari)of nitrate is-0.14 W/m~2 in 2010,and the high value regions are in East Asia,South Asia,Europe,and North America.When it comes to 2100,the RFari would be-0.044~-0.099 W/m~2 relative to 1850.The highest value of RFari appeared in summer or winter,this is the result of influence of solar zenith angle,relative humidity,cloud cover and surface albedo.(4)Since 1850,the Effective Radiative Forcing from aerosol–radiation interactions(ERFari)of nitrate is about-0.26W/m~2 by 2010,and it's a little bigger than the RFari.In 2100,the ERFari of nitrate would be about-0.054~-0.15/m~2 relative to 1850.