地基多波长激光雷达的温度自校正CO2廓线反演方法研究

The intense study of carbon flux and carbon cycle relies on high-precision vertical profile of atmospheric CO2, and the Differential Absorption Lidar (DIAL) for CO2 profile detection is widely recognized as an advanced technology. However, the dependence on strict laser frequency stabilization and the real-time atmospheric temperature data, as well as the limitation of the existing profile retrieval method, greatly limit the development and accuracy of traditional dual-wavelength DIAL. In order to solve the above problems, this project proposes a new CO2 profile retrieval method for the ground based multi-wavelength DIAL. On one hand, the sequential adjustment inversion framework based on the redundancy observation of multi-wavelength laser is constructed to overcome the dependence on laser frequency stabilization for traditional method. On the other hand, the temperature-sensitive wavelengths in the CO2 absorption spectrum is quantified, and the adaptive iterative algorithm for the temperature and CO2 profile, so as to do the CO2 retrieval based on temperature self-correction. Meanwhile, the influence of aerosol on inversion is taken into consideration, and a more advanced profile retrieval method is proposed，which can overcome the shortcoming of sacrificing space resolution of the traditional inversion method. This study is expected to provide a CO2 profile detection method with the unification of high precision and high resolution. Therefore, it can provide a technical reserve for the development of multi-wavelength CO2 detection DIAL, and provide the theoretical support for the application of high-precision remote sensing in the monitoring of carbon emission and research of carbon flux.

碳通量、碳循环的深入研究，依赖于CO2垂直廓线的准确获取，利用差分吸收激光雷达进行CO2廓线探测是国际公认的先进技术手段。但对激光稳频、实时大气温度廓线的依赖，以及现有廓线反演方法的局限，极大限制了传统双波长差分吸收激光雷达的应用研究与探测精度。针对上述问题，本项目拟发展一种全新的地基多波长差分吸收激光雷达的CO2廓线反演方法。一方面以多波长的技术手段克服传统反演对激光稳频的依赖，构建序贯平差反演框架；另一方面具化CO2吸收谱中的温度敏感波长，发展温度与CO2廓线的互迭代算法，进行温度自校正的CO2反演；同时充分考虑气溶胶对反演的影响，并克服传统反演牺牲空间分辨率的缺点，提出更先进的廓线反演方法。本研究成果有望提供高精度和高分辨率相统一的CO2廓线反演方法，为多波长CO2廓线探测激光雷达的研制提供技术储备，同时为高精度的遥感技术应用于碳排放监测和碳通量研究提供理论支撑。

二氧化碳（CO2）浓度上升引起的全球气候变化，是全球热点问题。其浓度廓线是碳循环研究中的关键数据。地基CO2探测差分吸收激光雷达（CO2-DIAL）可获得精确的CO2廓线。人类活动引起的碳排放强度大，同时具有多尺度空间变化和复杂时间变化特征，而一般激光雷达无法兼顾空间分辨率、灵敏度和时间连续性的多维度需求。针对上述问题，本项目开展的多波长CO2廓线观测激光雷达关键技术研究，能在获得温度廓线的同时，获得时间连续的、高精度、高距离分辨的CO2廓线。设计了多波长探测机制，一方面实现温度的测量，另一方面规避激光稳频，提出多波长信号的序贯平差反演算法，提高CO2廓线反演精度；最后以正交多项式拟合得到高距离分辨率的廓线。本项目的研究成果，将为多波长激光雷达的研制奠定理论基础，有望获得中小尺度内的高精度、高距离分辨率的全天时CO2廓线数据，为碳循环的科学研究、嗅探卫星的精度提高以及碳排放监测等提供可靠的手段，具有重要的科学意义和应用价值。