【作者】 曹贤洁；

【导师】 张镭；

【作者基本信息】 兰州大学 ， 大气物理学与大气环境， 2010， 博士

【摘要】 大气气溶胶通过直接效应、间接效应和半直接效应对区域和全球气候变化产生显著的影响,研究气溶胶辐射效应具有重要的现实意义,但也存在很大的不确定性,特别是沙尘气溶胶。在中国西北半干旱地区,由于特殊的地表下垫面特征,长期连续的气溶胶观测在气溶胶对气候变化的影响的研究中起支撑作用的一个关键环节。本文利用兰州大学半干旱气候与环境观测站微脉冲激光雷达CE370-2和偏振激光雷达L2S-SMⅡ观测资料,分析兰州地区气溶胶的垂直分布和时间演变特征。然后利用浑浊度仪、黑碳仪、PM10监测仪等地面观测资料研究了气溶胶散射系数、吸收系数和单次散射反照率等的变化特征。最后利用WRF+ABL+ LOWTRAN7数值模拟平台,对一次沙尘过程下兰州地区大气边界层特征和沙尘气溶胶的辐射特性进行了数值模拟。观测分析得到一些有价值的结果,可为气溶胶辐射效应数值模拟提供参考,有助于改进大气数值模式辐射参数化方案,具有重要的科学意义和应用价值。主要结论如下：（1）分析2005—2008年CE370-2观测资料,可知兰州地区11月和12月AOD最大,3月和4月的相对较大,且冬春AOD比夏秋的偏大,其主要由大气扩散条件和污染排放等因素决定。兰州地区AOD频数最大位于0.3。气溶胶集中分布在2km以下,且气溶胶消光系数随高度递减。（2）兰州地区沙尘气溶胶总体而言集中分布于2km以下,沙尘气溶胶消光系数随高度递减。个例分析表明：沙尘气溶胶层内,相对湿度和消光系数的变化趋势比较一致；沙尘过程中PM10浓度、气溶胶散射系数和消光系数间具有较好的线性相关性,PM10浓度和散射系数、PM10浓度和消光系数、消光系数和散射系数间的相关系数分别为0.98、0.94和0.96。（3）分析L2S-SMⅡ观测资料表明：云、冰晶和沙尘粒子的退偏振率较大,人为源气溶胶粒子的退偏振率较小；气溶胶粒子的退偏振率一般小于0.25,云和冰晶粒子的则为0.3左右。（4）利用2009年黑碳仪AE-31观测资料,分析了兰州地区黑碳气溶胶的变化特征。总体而言,黑碳气溶胶质量浓度呈双峰型日变化。夏秋和冬春上午的峰值时间略有差别,分别位于08：00和12：00,夜间均位于22：00,且谷值都位于16：00。七波段黑碳质量浓度变化趋势基本一致,且370nm的最大,950nm最小。月平均黑碳质量浓度呈U型分布,黑碳质量浓度自1月减小,3月和4月基本相当,于5月达到最小值,之后缓慢增大,6—8月和5月的差不多,9—12月急剧增大,最后于12月达到最大值。兰州地区冬春黑碳气溶胶质量浓度明显较夏秋偏大。黑碳气溶胶吸收系数的变化特征和黑碳质量浓度的比较一致。（5）利用2009年8—11月AE-31和MAAP5012观测资料,比较分析了两种黑碳仪的观测结果。AE-31 MAAP5012₁35和MAAP5012₁36观测结果具有较好的线性相关性。MAAP5012₁35和MAAP₁36观测结果的相关系数可达0.96, MAAP5012₁35和AE-31观测结果的相关系数为0.91, MAAP5012₁36和AE-31观测结果的相关系数为0.92。（6）利用2008年中美沙尘暴联合观测实验数据,分析了兰州和张掖地区SSA分布特征。兰州地区450和550nm的SSA频数分布较一致且最大值位于0.7,700nm则位于0.5。张掖地区三波段SSA频数分布相似,频数最大位于0.8。（7）利用WRF+ABL+LOWTRAN7数值模拟平台模拟分析了2007年3月27日—3月29日沙尘条件下兰州地区大气边界层特征和沙尘气溶胶辐射效应。沙尘过程盛行偏西风,局部地区偏北风,沙尘初期模拟区域北部地区存在上升运动,随着沙尘过程的发展下沉运动逐渐占据主导。位温的空间分布和地形分布比较接近,位温高值区位于地势较高处,谷地的位温相对较小。谷地的相对湿度较高地势处的偏大。沙尘气溶胶的辐射效应在日间表现为增温效应且使风速增大,增温幅度平均约为0.39-C,风速增幅约为0.57m／s；夜间,lkm以下表现为冷却效应并使风速减小,温度平均减小约为0.4-C,风速平均减小约0.56m／s,1km以上为增温效应并使风速增大,温度增幅平均约为0.35℃,风速增幅约为0.47m／s。更多还原

【Abstract】 The atmospheric aerosol plays a crucial role in the global and regional climate change by its direct, indirect, and semi-direct effect. Due to the inhomogeneous temporal and spatial distribution of aerosol it has significant uncertainties in the research of aerosol radiative effect, especially for the dust aerosol, but it has no doubt that the study of aerosol radiative properties makes significant scientific senses, In the semiarid area of northwest China with special surface underlying, the aerosol observation in long-term and continuity is one of the key and fundamental elements in the study of the aerosol impacts on climate change.The vertical distribution and temporal evolution of aerosol over Lanzhou are analyzed using the data of micropulse lidar CE370-2 and depolarization lidar L2S-SMⅡat the Semi-Arid Climate and Environment Observatory of Lanzhou University （SACOL）. Then the thesis presents the variation properties of aerosol scattering coefficient, absorption coefficient, and single scattering albedo using the measurements of nephelometer, aethalometer, multi-angle absorption photometer, PM10 particulate monitor et al.. Finally, a numerical simulation of the atmospheric boundary meteorological conditions and dust aerosol radiative properties over Lanzhou during a dust storm is carried out using the WRF+ABL+LOWTRAN7 models system. In all, some valuable results are retrieved, which would be the references for the numerical simulation of aerosol radiative effect and improve the radiation schemes in the atmospheric numerical models. The work surely has important scientific senses and values. The main results are as follows.（1） Statistic analysis of micropulse lidar CE370-2 observation since 2005 to 2008 shows that the maximum aerosol optical depth （AOD） appears in November and December, and AOD in March and April are some bit large, AOD is larger in winter and spring than in summer and fall, which is mainly determined by the conditions of local atmospheric diffusion and pollution emissions. The frequency analysis presents that the AOD mostly ranges around 0.3. As to the vertical distribution of aerosol over Lanzhou, it is mainly concentrated below 2 km height, and the aerosol extinction coefficient decreases with height.（2） The dust aerosol is mostly distributed under 2 km height, and the dust aerosol extinction coefficient decreases with height. The case study shows:In the dust aerosol layer, the aerosol extinction coefficient and relative humidity have the similar variation trends; It has linear correlations among PM10 concentration, aerosol scattering and extinction coefficients, and the correlation coefficient between PM10 concentration and aerosol scattering coefficient, between PM10 concentration and extinction coefficient, between extinction coefficient and scattering coefficient is 0.98 0.94 and 0.96 respectively.（3） Using the data of depolarization lidar L2S-SMⅡ, the depolarization ratios of aerosol and cloud are analyzed. The depolarization ratios of cloud, ice, and dust aerosol are larger than anthropogenic aerosol. The aerosol depolarization ratio is below 0.25, while that of the cloud and ice mostly range around 0.3.（4） The black carbon （BC） mass concentration and absorption coefficient are analyzed using the measurement of aethalometer AE-31 in 2009. The BC mass concentration at 7 wavelengths have the similar variation trends, and the BC mass concentration of 370 nm is largest, while the BC mass concentration of 950 nm is the smallest. As to the diurnal evolution of BC mass concentration, the maximum appears at 08:00 and 12:00 respectively in the daytime of summer and fall, and winter and spring,22:00 in nighttime. The minimum appears at 16:00. The monthly average of BC concentration’s variation shows the U distribution. It decreases since January till the minimum in May, then increases and reaches the maximum in December. It also presents that the BC mass concentration is larger in winter and spring than in summer and fall. As to the BC absorption coefficient, it has the similar variation trend with that of BC mass concentration.（5） Using the data of aethalometer AE-31 and multi-angle absorption photometer （MAAP） 5012 since August to November 2009, the comparison between two measurements presents a good linear correlation. The correlation coefficient between the retrievals of MAAP5012₁35 and MAAP5012₁36, between the retrievals of MAAP5012₁35 and AE-31, and between the retrievals of MAAP5012₁36 and AE-31 is 0.96,0.91 and 0.92 respectively.（6） The frequency distribution analysis of single scattering albedo （SSA） over Lanzhou and Zhangye are carried out using the data of 2008 China-US joint dust storm observation experiment. Over Lanzhou, the SSA of 450 and 550 nm have the similar frequency distributions, and the maximums frequency of SSA at 450 and 550 nm appear at 0.7, while 0.5 for the SSA of 700 nm. As to the SSA frequency distributions over Zhangye, they show similar frequency distributions at 450,50, and 700 nm, and the maximums appear at 0.8.（7） Using the numerical simulation platform of WRF+ABL+LOWTRAN7, the atmospheric boundary meteorological conditions and dust aerosol radiative properties are presented. During the dust storm, the west wind is prevailing in most simulation distract. In the north of simulation area, it has upward motion, as the development of dust storm the downward motion is dominated.The distribution of potential temperature has a good agreement with that of terrain, higher potential temperature is located on higher terrain and the lower seats on the valley. As to the relative humidity, it is opposite to that of potential temperature.The dust aerosol has warming effect in daytime, the temperature increases by 0.39℃. In nighttime, it presents cooling effect under 1 km, and the temperature decreases by 0.4℃，and in the layer above 1 km the dust aerosol has warming effect, the temperature increases by 0.35℃. As to the wind conditions, the dust aerosol increases the wind speed by 0.57 m/s in daytime. In nighttime, the wind speed decreases by 0.56 m/s below 1 km, and increases by 0.47 m/s above 1 km.更多还原