多轴差分吸收光谱技术测量近地面NO2体积混合比浓度方法研究

多轴差分吸收光谱技术(MAX-DOAS)通过测量不同角度的太阳散射光, 获取痕量气体的柱浓度信息, 广泛应用于整层NO₂柱浓度的监测. 由于缺少有效观测距离的信息, MAX-DOAS无法获取近地面NO₂的体积混合比浓度. 本文分析了消光系数和有效观测距离的关系, 提出了利用能见度信息获取有效观测距离, 进而将MAX-DOAS测量的水平方向NO₂斜柱浓度转换为体积混合比浓度的方法. 并在合肥开展了相应的观测实验, 成功实现了基于MAX-DOAS的NO₂体积混合比浓度测量. 通过与主动式长程差分吸收光谱仪测量的NO₂浓度进行对比, 结果呈现出较好的一致性, 说明了方法的可行性.研究为MAX-DOAS监测近地面NO₂体积混合比浓度提供了一种简单有效的方法, 拓展了MAX-DOAS的应用领域. 关键词： 多轴差分吸收光谱技术 大气消光系数 能见度 2体积混合比浓度')" href="#">NO₂体积混合比浓度

Retrieval of surface NO2 mixing ratio from multi-axis differential optical absorption spectroscopy

The multi-axis differential optical absorption spectroscopy (MAX-DOAS) technique, in which solar scattered light beams of different elevation angles are used and the spatial distribution of various trace gases is derived, has been widely used for monitoring the NO₂ slant column density. Due to the lack of information in a detectable horizontal range of the MAX-DOAS instrument, the concentration of trace gases including NO₂ is unable to yield directly. In this work, the relationship between extinction coefficient and light path length of MAX-DOAS observation is analyzed, and a retrieval algorithm to convert the horizontal NO₂ differential slant column density into the volume mixing ratio with the information of visibility is described. This algorithm has been used in the MAX-DOAS observation at Hefei, and volume NO₂ mixing ratio is derived from MAX-DOAS measurement combining the data of visibility. The NO₂ concentration measured with MAX-DOAS shows that it is in good agreement with the result obtained with long path differential optical absorption spectroscopy, proving the feasibility of the retrieval method. This research presents a simple and effective monitoring method of volume NO₂ mixing ratio with MAX-DOAS, there by expanding the application scope of MAX-DOAS technique.