长三角背景区域相对湿度对大气气溶胶散射特征影响的观测与模拟研究

发布时间：2018-12-14 12:29

【摘要】：气溶胶吸湿特征的准确描述对于减小气溶胶辐射强迫评估中的不确定性、更准确地模拟气溶胶辐射强迫和大气能见度都有非常重要的意义。本研究于2014年8月-2015年7月在临安大气区域本底站进行了为期一年的气溶胶散射吸湿增长特征观测。研究发现,临安地区气溶胶散射系数σsp、后向散射系数σbsp和吸收系数σap(550 nm波长下)年平均值分别为197±147 Mm~(-1)、26±17 Mm~(-1)和20±15 Mm~(-1)。单次散射反照率、半球后向散射比和?ngstr?m指数的年平均值为0.89±0.04,0.14±0.02和1.63±0.28。80%相对湿度下年平均散射吸湿增长因子f(80%)、后向散射吸湿增长因子fb(80%)和后向散射比吸湿增长因子fb(80%)分别1.71±0.161、1.29±0.085和0.78±0.037,向上散射比β?由干状态下的0.271±0.016降低到80%的0.236±0.016,气溶胶吸湿能力冬春较高、夏秋较低。临安地区气溶胶散射吸湿增长数据可由参数化公式f(RH)=1+aRHb较好模拟,按照不同散射吸湿增长特征分类给出了参数化拟合结果。研究验证了粒径吸湿增长因子g(RH)不同计算方法(a)Petters和Kreidenweis(2007)的κ-K?hler简化公式、(b)Tang(1996)的经验公式和(c)ISORROPIA II模型在临安散射吸湿增长模拟中的可行性,可以为模式模拟、辐射计算和遥感资料分析等提供有用信息。敏感性实验表明化学组分通过影响气溶胶粒径吸湿增长因子g(RH)是气溶胶散射吸湿增长因子最重要的影响因子,其次是气溶胶数浓度谱的中值粒径和谱宽,干状态下气溶胶的复折射指数的实部和虚部均对气溶胶散射吸湿增长因子影响很小。对于临安地区,当环境相对湿度高于60%时极易发生霾,一旦干状态下散射系数超过100 Mm~(-1),大气能见度就极有可能低于10 km;环境湿度高于80%时,临安极易发生重度霾,一旦干状态下散射系数超过100 Mm~(-1),大气能见度极有可能低于5 km。研究定量评估了气溶胶在环境相对湿度下吸湿增长吸收水分对大气总消光及气溶胶直接辐射强迫的贡献。研究时段临安大气环境相对湿度年平均值为78.9%,由于气溶胶在环境湿度下吸湿增长吸收水分造成大气散射的增加对大气消光的贡献的年均值~41%;80%相对湿度下气溶胶直接辐射强迫是干状态下气溶胶直接辐射强迫的1.57倍,在临安地区全年的观测中,由于气溶胶在环境相对湿度下吸湿增长吸收水分造成的气溶胶直接辐射强迫与干状态下气溶胶直接辐射强迫的比值约1.3-1.9,气溶胶吸湿增长吸收水分对气溶胶直接辐射强迫的贡献约为23%-47%。
[Abstract]:The accurate description of aerosol moisture absorption characteristics is very important for reducing the uncertainty in aerosol radiation forcing assessment and simulating aerosol radiation forcing and atmospheric visibility more accurately. From August 2014 to July 2015, the characteristics of aerosol scattering and moisture absorption growth were observed at the background station of Linan atmospheric region for a period of one year. It is found that the annual mean values of aerosol scattering coefficient 蟽 sp, backscattering coefficient 蟽 bsp and absorption coefficient 蟽 ap at 550 nm wavelength are 197 卤147 Mm~ (-1), 26 卤17 Mm~ (-1) and 20 卤15 Mm~ (-1), respectively. The annual mean values of single scattering albedo, hemispheric backscattering ratio and? ngstr?m exponent are 0.89 卤0.04g 0.14 卤0.02 and 1.63 卤0.28.80% relative humidity respectively. The backscattering hygroscopicity growth factor fb (80%) and backward scattering specific hygroscopicity growth factor fb (80%) were 1.71 卤0.161g 1.29 卤0.085 and 0.78 卤0.037, respectively. From 0.271 卤0.016 in dry state to 0.236 卤0.016 in 80%, the moisture absorption ability of aerosol is higher in winter and spring, and lower in summer and autumn. The aerosol scattering and moisture absorption growth data in Linan area can be well simulated by the parameterized formula f (RH) = 1 aRHb, and the parameterized fitting results are given according to the different characteristics of scattering moisture absorption growth. The simplified formula of 魏-K?hler for (a) Petters and Kreidenweis (2007) in different calculation methods of particle size moisture absorption growth factor (g (RH) was verified. The feasibility of the empirical formula and (c) ISORROPIA II model of (b) Tang (1996 in the simulation of moisture absorption growth in Lin'an scattering can provide useful information for model simulation, radiation calculation and remote sensing data analysis. The sensitivity experiment shows that the chemical component is the most important factor of aerosol scattering hygroscopicity growth factor (g (RH), followed by the median particle size and spectrum width of aerosol number concentration spectrum. Both the real and imaginary parts of the aerosol complex refraction index have little effect on the aerosol scattering hygroscopicity growth factor in dry state. For Lin'an area, haze is easy to occur when the relative humidity is higher than 60. Once the scattering coefficient exceeds 100 Mm~ (-1) in dry state, atmospheric visibility is likely to be less than 10 km;. When the ambient humidity is higher than 80, the severe haze is easy to occur in Linan. Once the scattering coefficient exceeds 100 Mm~ (-1) in dry state, the atmospheric visibility is likely to be lower than 5 km.. The contribution of moisture absorption growth of aerosols to total atmospheric extinction and aerosol direct radiation forcing was quantitatively evaluated. The annual average value of atmospheric relative humidity in Linan is 78.9. The annual mean value of the contribution of atmospheric scattering to atmospheric extinction due to the increase of moisture absorption and water absorption by aerosols at ambient humidity is ~ 41. The direct radiative forcing of aerosol at 80% relative humidity is 1.57 times higher than that under dry condition. The ratio of aerosol direct radiation forcing to aerosol direct radiation forcing in dry state is about 1.3-1.9 due to the increase of moisture absorption under relative humidity. The contribution of aerosol moisture absorption to aerosol direct radiation forcing is about 23-47.
【学位授予单位】：中国气象科学研究院
【学位级别】：博士
【学位授予年份】：2017
【分类号】：X513

【参考文献】