【作者】 邓学良；

【导师】 潘德炉； 孙照渤；

【作者基本信息】 南京信息工程大学 ， 气象学， 2008， 博士

【摘要】 气溶胶作为重要的气候因子,对地-气能量系统产生重要的影响。本论文主要是结合多颗传感器的卫星数据(MODIS气溶胶产品和CERES辐射通量数据),系统地分析了中国海域气溶胶的光学特性和辐射强迫。首先利用船测数据和AERONET地基观测数据,通过改进了测量方法和验证方法,对MODIS气溶胶产品在中国海域的适用性进行了验证;然后利用验证后的MODIS数据,分析了我国海域气溶胶的时空分布特征,并结合气象场和化学成分进行了原因说明;进一步利用MODIS气溶胶产品,分离出人为气溶胶和沙尘气溶胶成分,并得到它们的时空分布特征;结合MODIS、CERES数据和辐射传输模式,设计了气溶胶直接辐射强迫的算法,得到中国海域气溶胶直接辐射强迫的分布,并与SPRINTARS气溶胶模式结果进行了比较;最后利用MODIS的气溶胶和云产品,对我国海域气溶胶的间接作用进行了分析。得到以下主要结论:1.改进太阳光度计测量方法,对中国海域气溶胶进行了船载测量,验证了MODIS气溶胶光学厚度的分布特征;利用AERONET数据,改进验证方法,证实MODIS气溶胶光学厚度与AERONET具有很好的相关关系,误差符合NASA的要求,说明MODIS气溶胶产品适用于中国海域。这为下面的研究打下了基础。2.通过分析MODIS气溶胶产品,证实我国海域气溶胶光学厚度(AOT)与小颗粒比例(FMF)存在明显的季节变化和空间分布特征。通过分析气象场和化学成分可知,这一特征受风场和降雨的影响,而陆源输送是我国海域气溶胶的主要来源。3.利用MODIS气溶胶产品中AOT与FMF的关系,得到了人为和沙尘气溶胶的计算公式,利用这一公式分别获得中国海域人为和沙尘气溶胶各自的分布。分析结果显示,中国海域人为气溶胶和沙尘气溶胶分别存在明显的时空分布特征。4.结合MODIS、CERES数据和辐射传输模式,设计了计算直接辐射强迫的算法:(1)剔除云区;(2)建立无气溶胶晴空条件下的大气顶辐射通量查找表;(3)将辐射率转化为辐射通量;(4)计算气溶胶瞬时直接辐射强迫;(5)计算瞬时辐射强迫与日平均辐射强迫之间的修正因子。通过以上五步,得到了中国海域气溶胶直接辐射强迫的时空分布特征。并通过与SPRINTARS气溶胶模式结果的比较,证实了利用卫星直接计算我国海域气溶胶直接辐射强迫是可行的。5.通过分析MODIS的气溶胶和云产品,证实了我国海域气溶胶间接效应是明显存在的。在不同季节由于气溶胶种类的变化和水汽条件的不同,气溶胶对于云的间接作用又是不同的。本论文的主要创新点:1.对MODIS气溶胶产品的验证方法进行了改进。首先,通过改进MICROTOPSⅡ的测量方法,将适合于陆地测量的太阳光度计应用到海上船载测量。其次,改进了MODIS与AERONET的验证方法,调整了空间匹配窗口的大小,得到了更好的验证效果。2.结合气象场和化学成分数据,分别从气象因素和化学组成两个方面分析了我国海域气溶胶的形成原因。分析可知,我国海域气溶胶主要来源于我国沿海的陆地源,受到风场和降雨的共同作用,形成明显的时空分布特征。3.利用MODIS气溶胶产品中的AOT和FMF关系,得到了沙尘气溶胶和人为气溶胶的计算公式,直接从卫星数据中区分了沙尘气溶胶和人为气溶胶成分。4.在国内首次结合多颗传感器的卫星数据,直接获得气溶胶瞬时直接辐射强迫。并利用辐射传输模式,将瞬时直接辐射强迫转化为日平均直接辐射强迫。最后利用卫星数据证实了中国海域气溶胶的间接效应的存在。更多还原

【Abstract】 Atmospheric aerosol plays an important role in the global and regional climate change. It has a significant impact on the solar radiation budget. In this dissertation, aerosol optical characteristics and aerosol radiative forcing over the China Sea are analyzed directly by satellite data, including MODIS and CERES. Firstly, MODIS aerosol product is validated over the China Sea by ship-based measurements and AERONET data. Then temporal and spacial distributions of aerosol over the China Sea are discussed by MODIS aerosol product and formation mechanism of their distribution is explained by meteorological data and chemical composition. Furthermore, based on relationship between fine mode fraction(FMF) and aerosol optical thickness(AOT) in MODIS, anthropogenic component and dust component of aerosol can be respectively computed from satellite data. Meanwhile, the algorithm for getting aerosol direct forcing by satellite data is proposed. Characteristic of the algorithm is combination of different satellite data and radiance transfer model. Aerosol direct forcing over the China Sea is computed by this algorithm and then the algorithm’s results are compared with results of Spectral Radiation-Transport Model for Aerosol Species (SPRINTARS). In final, aerosol indirect forcing over the China Sea is discussed by MODIS aerosol product and cloud product. Some significant results are revealed as follows:1. Aerosol optical characteristics are observed over the China Sea by improved ship-based measurement method, which validates distribution feature of MODIS aerosol product. At the same time, values of MODIS aerosol product are validated by AERONET data with an improved method. The result shows that they have a good relationship and the error between them is within NASA required standard. This provides importance scientific argument for aerosol research over the China Sea.2. Spatial distribution feature and season variation characteristic of aerosol over the China Sea are notable by MODIS data. Then analysis of meteorological data and chemical composition shows that they are influenced by wind and rainfall and continental region is main source of aerosol over the China Sea.3. An algorithm for separating anthropogenic component and dust component from MODIS data is proposed on the basis of the relationship between AOT and FMF. Results of this algorithm show that anthropogenic aerosol and dust aerosol over the China Sea exist prominent season variation and spatial distri(?)ution feature.4. Based on MODIS、CERES and radiance transfer model, an algorithm, which is used for computing aerosol direct forcing over the China Sea, is proposed. The algorithm is meaning in physics by five steps: (1) separating of cloud and clear region; (2) generating the Look-up-tables (LUT) of radiation flux at the top of atmosphere in the clear sky without aerosol; (3) converting radiance to radiation flux; (4) computing instantaneous aerosol direct forcing; (5) computing scaling factor to convert instantaneous aerosol direct forcing to diurnally averaged values. Using these five steps, aerosol direct forcing over the China Sea is gained and then it is compared with Spectral Radiation-Transport Model for Aerosol Species (SPRINTARS). The result shows the algorithm is possible and feasible.5. Aerosol indirect forcing does exist over the China Sea by analysis of MODIS aerosol product and cloud product. Because of different aerosol kinds and water vapor amounts at different seasons, aerosol indirect forcing over the China Sea expresses different features.Some innovations is listed as follow:1. The validation method is improved. Firstly, ship-based measurement method is modified. Though altering MICROTOPS II parameters, sun photometer is applied to observe over the China Sea. Secondly, validation method between MODIS and AERONET is improved by modifying space windows. The validation result is better than before.2. Formation mechanism of aerosol distribution feature over the China Sea is explained by combination of meteorological data and chemical composition. Aerosol over the China Sea comes from the China continent and is influenced by wind and rainfall. 3. Using relationship between AOT and FMF in MODIS, anthropogenic component and dust component of aerosol can be respectively computed from satellite data.4. Aerosol direct forcing over the China Sea is first studied by combination different satellite data in home. And through scaling factor, instantaneous aerosol direct forcing is converted to diurnally averaged values. Meanwhile, Aerosol indirect forcing is validated by MODIS data over the China Sea.更多还原