Study On Aerosol Optical Characteristics And Aerosol Radiative Forcing By Remote Sensing Over The China Sea

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.