Research On Spaceborne Detection Methods For Atmospheric Carbon Dioxide Concentration

With today's global warming growing, measurement of atmospheric carbon dioxide concentration has been concerned by many countries. The technologies of detection are primarily based on ground, airborne platform and space platform.The existing ground observation network can provide high-precision measurement results, useful system parameters and transmission models. However, small ground coverage and the lack of measuring data of the southern hemisphere make it impossible to explain the phenomenon of sources and sinks of carbon dioxide. CO₂ fluxes generally occur in the troposphere, so when aircraft is detecting in the stratosphere, high-precision results can be obtain. But compared with coverage of the whole world, it also appears to be limited.The main advantages of spaceborne detection, such as measurement results of high precision, global coverage and free from spatial and temporal limits, the ways of calibration with ground-based and airborne platform data, are considered to be tremendous breakthrough. Its goal is measuring global changes of carbon dioxide concentration and mapping carbon dioxide sources and sinks. So this thesis is concerned with the methods research on spaceborne detection of atmospheric carbon dioxide concentration.Firstly, thesis reviews the research progress of atmospheric CO₂ concentration detection at home and abroad. Three measuring ways based on ground, airborne platform and space platform are described and development of satellite detection technology is also evaluated. Spectral detection and differential absorption technique are stated and based on which, the ideas of passive and active sensing are given. With the combination of two ideas, the basic principle of the compounding detection is derived. CO₂ concentration solution algorithm is constructed and divided into two algorithms of relative value and relative detection. The former describes the basic principle of relative value algorithm and radiative transfer models, while the the latter one establishes theoretical model of relative detection. For calibration, double-calibration method based on ground laboratory and observatory is proposed and expression is also given.Based on basic principle of passive detection and considerations of absorption spectral selection, satellite detection mode and optical system design, method of the passive detection of atmospheric carbon dioxide concentration has been proposed and evaluated. Meanwhile, from the differential absorption principle, the thesis analyses the selecting reasons of dual-wavelength and design of satellite detection system, and then establishes scheme of the active sensing. Then it also estimates the advantages of active sensing and discusses key points needed to be improved.With the combination of both passive and active detection technology, the environmental impacts of the satellite dynamics are analyzed and calculated, at the same time, accuracy requirements are proposed and sources of error are analysed. Finally, the method of spaceborne compounding detection of atmospheric carbon dioxide concentration is given and relevant parameters are designed.This paper can benefit scheme choices for detection of atmospheric carbon dioxide concentration, and provide a new way to build CO₂ spaceborne detection system.