| The increasing concentration of greenhouse gases in the atmosphere intensifies the greenhouse effect,resulting in significant changes in the Earth’s climate and environment,which seriously affects human living conditions.Therefore,it is urgent to control greenhouse gas emissions.Comprehensive and accurate understanding of greenhouse gas concentration and emission data in the atmosphere is of great significance for evaluating the greenhouse effect and formulating emission reduction measures.Weighting Function Modified Differential Optical Absorption Spectroscopy(WFM-DOAS)technology,which has the characteristics of non-contact measurement,high measurement accuracy,and simultaneous measurement of multiple components,can achieve precise measurement and evaluation of various greenhouse gases.This paper conducted a study on the remote sensing of carbon dioxide concentration distribution based on near-infrared differential absorption spectroscopy technology and estimated the emission flux of typical emission sources.The main research contents include the following aspects:1.A near-infrared differential absorption spectroscopy retrieval method for the main greenhouse gas(CO2)concentration was investigated.The column weighting function and solar radiation normalized simulated spectra of gas were obtained by atmospheric radiation transmission model.The effects of input parameters such as spectral resolution,integration step,output height,and zenith angle on the column weighting function were analyzed and optimized.We selected the retrieval wavelength range of 1590-1620 nm for CO2 and used a least squares fitting method to retrieve the CO2 column concentration using the actual measurement spectra,column weighting function,and solar radiation normalized simulated spectra.2.A ground-based remote sensing system based on near-infrared differential optical absorption spectroscopy technology was built and observation research on typical greenhouse gas emission sources was conducted.We used bicubic interpolation algorithm to optimize the scanned remote sensing results and obtained high spatial resolution CO2 column concentration distribution of power plant emissions.We estimated the emission flux of CO2 from the power plants.The amount of CO2 emitted per hour by Feidong Power Plant was about 4140 kg,while that emitted by Fengtai Power Plant was about 32490 kg.We conducted remote sensing research on the distribution of urban CO2 concentration in a complex atmospheric background and obtained the CO2 boundary layer concentration distributions in the suburban area,power plant area,and urban area of Hefei.The results showed that the high values of CO2 concentration were mainly located near the ground,the height of the high value layer was about 140～400 m,and the CO2 concentrations in the power plant and urban areas were significantly higher than that in the suburban area.3.A ground-based direct-sunlight WFM-DOAS measurement system was constructed to investigate the column concentration of CO2 in the ambient atmosphere.A near-infrared spectroscopic receiving system coupled with a small aperture telescope and quartz fiber was designed,and in combination with the equatorial instrument a high-precision solar tracking system was integrated,achieving a tracking accuracy of 1 arcminute/day.Using this measurement system,remote sensing research on the vertical column concentration of CO2 in the ambient atmosphere was conducted in Hefei,and the column concentration results were obtained continuously during the observation period with a fitting error of less than 1%.The observed results were compared with the data from TCCON,with a correlation coefficient R of 0.81.The remote sensing system based on near-infrared differential absorption spectroscopy constructed in this study can quickly and accurately measure the concentration distribution of CO2 from typical emission sources with high spatial resolution,obtain the emission flux from typical emission sources,and provide an effective remote sensing evaluation technique for carbon emission monitoring. |
