摘要:
本文研究了多轴差分吸收光谱技术(MAX-DOAS)的云和气溶胶类型鉴别方法.首先研究了晴朗低气溶胶、晴朗高气溶胶、分散云、连续薄云和连续厚云下，色彩因子、光通量和O4的大气质量因子的变化特征.分析发现随着云和气溶胶光学厚度的增加，色彩因子会逐渐减小.分散云会使色彩因子发生快速变化，连续云会使各高度角的色彩因子趋于一致.另外，厚云会使天顶方向光强剧烈下降，同时O4大气质量因子大幅度增加.根据分析结果，最终形成了MAX-DOAS技术的云和气溶胶类型鉴别方案.利用该鉴别方案，统计分析了2012年6月1日到10月30日的MAX-DOAS观测结果.分散云和连续薄云出现频率最高，达到了66%和14.3%.两种类型下， NO2对流层垂直柱浓度(VCD)的平均值相对晴朗低气溶胶下高出35%和66%.而表征NO2 VCD测量值稳定度的标准偏差大约增大了2倍.连续厚云下NO2 VCD常出现突然的极大值和极小值.因此实时判别云和气溶胶的种类，将对MAX-DOAS数据的解析和数据质量的保证起到十分重要的作用.
Abstract:
The classification of cloud and aerosol by means of multi-axis differential optical absorption spectroscopy (MAX-DOAS) is studied in this paper. Firstly, the characters of variation of color index (CI), radiance, and O4 air mass factor (AMF) are analyzed in the following kinds of weather cases, i.e. “clear and low aerosol load”, “clear and high aerosol load”, “broken cloud”, “continuous and thin cloud” as well as “continuous and thick clouds”. We found that the CI consecutively decreases with the growing up of optical depth of cloud and aerosol. And the speedy temporal variation of CI is always going along with the occurrence of broken cloud. For the case of continuous cloud, the CIs of observations for all the elevation angles are similar to each other. At the same time, the thick cloud case normally causes radiance dropping and O4 AMF growing up strongly. Based on these characters, the scheme of cloud classification for MAX-DOAS is built. Using this scheme, the classification results for the MAX-DOAS observations in the period from 1 June 2012 to 30 October 2012 are analyzed statistically. The occurrence probabilities of the broken cloud and thin continuous cloud are the two largest weather kinds. The percentage of the broken cloud in all the observations is 66%, and that of the thin continuous cloud case is 14.3%. For these two kinds of weathers, the mean NO2 tropospheric vertical column densities (VCD) are respectively 35% and 66% larger than the value for the clear and low aerosol. Meanwhile, the standard deviation, which represents the stability of the measured NO2 VCD is two times larger than that of the clear and low aerosol cases. In the weather of thick continuous cloud, suddenly appearing of peak and valley are often observed. In conclusion, the real time classification of cloud and aerosol is very important and valuable in analyzing of MAX-DOAS data and the guarantee of data quality.
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