【作者】 王志立；

【导师】 张华； 沈学顺；

【作者基本信息】 中国气象科学研究院 ， 气象学， 2011， 博士

【摘要】 工业革命以来,人类活动造成的大气中气溶胶的含量显著增加。气溶胶能够直接吸收和散射红外和太阳辐射,扰动地气系统的能量收支,还能够作为云凝结核或冰核,改变云的微物理和辐射性质以及云的寿命,间接影响气候系统。尽管目前观测已经有了很大进步,但是想要通过观测评估气溶胶不同气候效应的影响非常困难。本论文在中国气象局国家气候中心大气环流模式BCC_AGCM2.0.1单向驱动中国气象科学研究院大气成分观测与服务中心研发的气溶胶理化数值模式CUACE_Aero的工作基础上,将其双向耦合,实现了一套气溶胶-辐射-气候在线耦合模式。利用该耦合模式模拟了典型种类气溶胶的浓度和光学性质,计算了气溶胶的辐射强迫,并讨论了气溶胶对全球和区域气候的影响。主要结论概括如下: （1）结合AEROCOM的气溶胶排放源数据,本文模拟的硫酸盐、黑碳、有机碳、沙尘和海盐气溶胶的全球年平均柱含量分别为1.74 mg m^-2、0.14 mg m^-2、1.31 mg m^-2、40.8 mg m^-2和14.7 mg m^-2。除了在南美洲模拟的光学厚度偏低外,模拟的总的气溶胶（包含硫酸盐、黑碳、有机碳、沙尘和海盐）的光学厚度、单次散射比和非对称因子与AERONET（AEROSOL ROBOTIC NETWORK）观测结果基本一致。模拟的单次散射比和非对称因子与观测值的平均偏差分别为4%和5%。（2）模拟的总的气溶胶和三种主要由人为活动引起的气溶胶（硫酸盐、黑碳和有机碳）在大气顶的直接辐射强迫的全球年平均值分别为-2.03 W m^-2和-0.23 W m^-2。其中,硫酸盐、黑碳、有机碳、沙尘和海盐气溶胶在大气顶的全球年平均直接辐射强迫分别为-0.19 W m^-2、+0.1 W m^-2、-0.15 W m^-2、-0.9 W m^-2和-0.83 W m^-2。总的气溶胶的直接和半直接效应造成全球大气顶和地表年平均净短波辐射通量分别减少3.1 W m^-2和3.9 W m-2,地表温度降低1.6oC,降水率减弱0.14 mm day-1。硫酸盐、黑碳和有机碳三种气溶胶在东亚地区造成的大气顶和地表夏季平均的直接辐射强迫分别为-1.4 W m^-2和-3.3 Wm^-2,从而导致东亚地区夏季平均地表温度降低0.58oC,降水率减少0.15 mm day-1。上述三种气溶胶的直接和半直接效应造成夏季东亚季风区陆海表面温度和气压差减弱,局地环流发生变化,从而导致东亚夏季风减弱,中国东部和南部夏季风降水减少。（3）模拟的气溶胶第一类间接辐射强迫在大气顶的全球年平均值为-1.57 Wm^-2,气溶胶第二类间接效应造成大气顶净短波辐射通量变化的全球年平均值约为-0.58 W m-2。气溶胶总的间接效应造成大气顶年平均净短波辐射通量降低2.27 Wm^-2,地表温度下降约0.12 oC,降水率减少0.03 mm day-1。在夏季,气溶胶总的间接效应造成中国东部和南部以及周围海洋上东北或偏北气流增强,从而减弱了东亚夏季风对水汽的输送,造成中国东部和南部地区降水减少。（4）雪和冰中黑碳气溶胶造成的全球年平均地表辐射强迫为+0.042 W m^-2,最大辐射强迫位于青藏高原上,年平均强迫超过+2.8 W m^-2。由于增强了雪和冰对太阳辐射的吸收,雪和冰中黑碳气溶胶造成全球年平均地表温度升高了0.071 oC。地表正辐射强迫在冬春季节就明显产生,导致北半球陆地上雪冰表面温度明显升高,雪融率增强,造成雪和冰提前融化。随着北极表面温度的升高,导致更多的水汽进入大气,从而使得北极上空总云量明显增加。增加的云量发射出更多的长波辐射到达地表,形成一种正反馈机制。但是,云量的增多使得总的云辐射强迫减少,可能削弱一定量的云量增多–温度升高–地表长波辐射增强的正反馈机制。更多还原

【Abstract】 Atmospheric abundances of aerosols have increased since the preindustrial period due to anthropogenic activities. Aerosols can affect climate in several ways. First, aerosol particles can directly scatter or absorb infrared and solar radiation, thereby disturbing the energy budget of the earth-atmosphere system. Second, aerosol particles acting as cloud condensation or ice nuclei can change cloud microphysical and radiative properties and cloud lifetime, and hence indirectly affect the climate. It is very difficult to assess the impact of different effects of aerosols by measurements, although improvements have been made lately. Thus, we finish an on-line coupled model of aerosol?radiation?climate based on the AGCM developed by the National Climate Center of the China Meteorological Administration （NCC/CMA）, called BCC_AGCM2.0.1, unidirectionally driving a physical and chemical model of aerosols （CUACE_Aero） developed by the Center for Atmosphere Watch and Services of Chinese Academy of Meteorological Sciences in this work. The concentrations and optical properties of typical aerosols are simulated, and the radiative forcing of aerosols and their effects on global and regional climate are discussed based on the above coupled model. The major conclusions are as follows:（1） The simulated global annual mean column burdens of sulfate, black carbon （BC）, organic carbon （OC）, dust and sea salt are 1.74 mg m^-2, 0.14 mg m^-2, 1.31 mg m^-2, 40.8 mg m^-2and 14.7 mg m^-2, respectively, using the source emissions that are derived primarily from AEROCOM data. The simulated optical depth, single scattering albedo, and asymmetry parameter of total aerosols （including sulfate, BC, OC, dust, and sea salt） are basically consistent with AERONET observations, except for an obvious underestimated aerosol optical depth （AOD） over South America. The mean relative errors of the simulated single scattering albedo and asymmetry parameter against observations are 4% and 5%, respectively.（2） The simulated global annual means of direct radiative forcing （DRF） due to total aerosols and three species of aerosol mainly produced by human activities （sulfate, BC, and OC） at the top of the atmosphere （TOA） are -2.03 W m^-2 and -0.23 W m^-2 respectively, under all sky conditions. The global annual mean DRFs of sulfate, BC, OC, dust and sea salt at the TOA are -0.19 W m^-2, +0.1 W m^-2, -0.15 W m^-2, -0.9 W m^-2 and -0.83 W m^-2, respectively. The annual mean changes of the net shortwave radiative flux at the TOA and surface due to the direct and semi-direct effects of total aerosols are approximately -3.1 W m^-2 and -3.9 W m^-2, respectively. Consequently, the global annual means of the surface temperature and precipitation rate decrease by 1.6oC and 0.14 mm day-1, respectively.The summer seasonal average DRFs due to sulfate, BC, and OC in East Asia at the TOA and surface are -1.4 W m^-2 and ?3.3 Wm^-2, respectively, leading to decreases of 0.58oC and 0.14 mm d-1 in the summer means of surface temperature and precipitation rate in this area, respectively. The differences of land-sea surface temperature and surface pressure are reduced and the local circulation is changed in East Asian monsoon region due to the direct and semi-direct effects of these aerosols, thus leading to the weakening of East Asian summer monsoon, and moreover decreasing of the summer monsoon precipitation in south and east China.（3） The study yields a global annual mean of ?1.57 W m^-2 for the first indirect radiative forcing of aerosols at the TOA. The second indirect effect of aerosols leads to global annual mean changes in net shortwave flux of ?0.58 W m^-2 at the TOA. The total aerosol indirect effect （AIE） reduces the global annual means of net shortwave flux at the TOA, surface temperature and precipitation rate by 2.27 W m^-2, 0.12oC and 0.03 mm day-1, respectively. In summer, the northeasterly or northerly flows in most areas of east and south China and over the nearby oceans are enhanced due to the total AIE, which weakens the transport of warm and moist air carried by the East Asian summer monsoon, and decreases the summer monsoon precipitation in east and south China.（4） The results show that the global annual mean surface radiative forcing due to BC in snow/ice is +0.042 W m^-2, with maximum forcing found over the Tibetan Plateau and regional mean forcing exceeding +2.8 W m^-2. The global annual mean surface temperature is increased 0.071oC due to BC in snow/ice. Positive surface radiative forcing is clearly shown in winter and spring which increases the surface temperature of snow/ice in the Northern Hemisphere. Snow-melt rates are also increased greatly, leading to earlier snowmelt and peak runoff timings. With the rise of surface temperature in the Arctic, more water vapor could be released into the atmosphere, allowing for easier cloud formation, which could lead to higher thermal emittance in the Arctic. However, the total cloud radiative forcing could be decreased due to the increasing of cloud cover, which will offset some of the cloud positive feedback mechanism.更多还原