近年来，中国已成为世界SO2浓度最高的区域之一，特别是人口密集、工业发达的华北地区。多轴差分吸收光谱技术(MAX-DOAS)是近十几年来大力发展的用于测量大气污染物的有效手段。到目前为止，MAX-DOAS的应用主要集中在NO2、气溶胶等的遥感反演；而对于SO2，由于O3强吸收带的干扰，反演误差较大，研究的相对较少，尤其在华北地区复合型污染背景下，叠加高浓度气溶胶的影响，SO2的反演难度更大。.. 为此，本项目计划利用华北地区具有代表性的香河大气综合观测站内国际先进的MAX-DOAS仪器及其他相关辅助设备长期的观测资料，发展适于华北地区高浓度复合型污染状况的、快速收敛且稳定的SO2 MAX-DOAS反演算法，开展地基SO2垂直廓线及柱总量的同时反演；在此基础上通过地基验证来评估卫星遥感SO2产品在华北地区的数据质量，并利用MAX-DOAS反演的SO2垂直廓线对卫星数据进行改进。

In recent years, China is one of the largest SO2 generating countries in the world, especially in North China with dense population and growing industrial activities. Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS), with rapid development over the past few years, is an effective remote sensing technique to measure air pollutants. So far most efforts of MAX-DOAS application have been dedicated to retrieving atmospheric NO2 and aerosol, but studies that deal with SO2 retrieval are scarce due to substantial retrieval noise induced by the interfering species O3 with strong absorption band overlapping with those of SO2. Furthermore, the performance of SO2 retrieval particularly vertical profile becomes even worse in the presence of high concentration of aerosols over North China. .. This project proposes to develop SO2 retrieval scheme capable of deriving the total column and vertical profile simultaneously based on the advanced MAX-DOAS instrument together with ancillary observations situated at Xianghe Observatory. This algorithm is intended specifically for application in heavily polluted North China with high accuracy, rapid convergence and high stability. Moreover, this project is also sought to validate and improve satellite SO2 products with the help of ground-based MAX-DOAS observations.