Studies On Remote Sensing Of Aerosol And Trace Gas Vertical Distribution By The MAX-DOAS

With severe regional air pollution problem in china, fast and accurate monitoring of regional air pollution is needed effective research and prevention of air pollution. Even air quality monitoring stations have been built centering on the cities, actual situation of air pollution can’t been reported completely, causing the disagreement of air quality index and public intuitive feelings. Existing traditional point monitoring techniques can’t fulfill the requirement of research in the production, evolution and transfer of air pollution. Multi-axis differential absorption spectroscopy (MAX-DOAS) technology can measure the pollutant in the troposphere and stratosphere, and provide the information of aerosol and trace gas distribution, not just derive the pollutant distribution in large region, but also being used in the validation of satellite data in same observation mode. In this thesis research on the remote sensing of aerosol and trace gas vertical distribution by MAX-DO AS technique has been carried out.Solar scatter spectrum is collected with MAX-DOAS instrument developed in our laboratory. Key parameters of MAX-DOAS was tested, include the field of view, pointing precision, stray light, spectral calibration and so on, showing good performance for monitoring requirement. Also, intensive study on unique problems of MAX-DOAS technique was conducted. The interference of scatter was removed with polynomial fitting, the effect of Fraunhofer structures and Ring effect were eliminated, I0effect correction was performed during the cross section processing, and the fitting windows of NO2, O4was determined. Finally the slant column density (SCD) has been retrieved precisely. A MAX-DOAS intercomparison campaign was attended, which included the instrument from home and abroad, and lasted for16days, and result evaluated the performance and SCD retrieval precision of MAX-DOAS further. Precisely retrieval of SCD is the guarantee of the following profile calculation, and in this thesis the work paid particular emphasis on the retrieval of aerosol and trace gas distribution.Based on the character that O4SCD and intensity index contain the information of aerosol, research on the aerosol retrieval with MAX-DOAS was carried out. At first, as O4absorption cross section inaccuracy cause the error of SCD, and this problem is solved with simulation of radiative transfer model. Then, the sensitivity of aerosol retrieval was analysed. The relationship between O4SCD, intensity index and aerosol, elevation angle was summarized, and the sensitivity was quantized with the weighting function. An aerosol extinction profile retrieval algorithm has been developed based on the optimal estimation method (OEM). The algorithm was validated with SCIATRAN simulated data, and result showed that the aerosol in the low troposphere can be derived precisely with this algorithm. The averaging kernel matrix was introduced for analyzing the effect of measurement noise and a priori information on the uncertainty of retrieval solution, and error analysis of the retrieval algorithm were carried out too.On account of that trace gas vertical distribution information can be derived from several SCD of different elevation angles, research on the trace gas profile retrieval wilh MAX-DOAS was carried out At first, the sensitivity of NO2SCD on the variation of profile is analysed in this thesis. For the speciality of weak absorption of NQ2, NO2vertical profile retrieval was fulfilled with linear optimal estimation method. Then the retrieval algorithm was validated with SCIATRAN simulated data, showing that this algorithm can be used for the the NO2profile retrieval below1km. The averaging kernel matrix was also introduced for analyzing the effect of measurement noise and a priori information on the uncertainty of retrieval solution, and used for error analysis. Moreover, a fast convert method from SCD to NO2concentration was developed.Field campaigns with developed MAX-DOAS instrument were held. Measurement result of aerosol extinction profiles showed that the particulate matter in Shanghai concentrated below1km, and the height of boundary layer was steady. Through the validation with Lidar, good agreement proved the feasibility of aerosol retrieval. The result of NO2vertical profile was also derived, and the concentrations of the lowest layer were validated with point measurement data. Furthermore, surface NO2mixing ratio information was derived based on the visibility data.