The distribution of water vapor with altitude has long remained a missing piece of the observational data set of water vapor on Mars. In this study, we present the first multi‐annual survey of water vapor profile covering the altitude range from 0 to 100 km based on the SPICAM/Mars Express occultation measurements. During the aphelion season, water remains confined below 40–60 km for all Martian years observed. The highest altitude where water vapor can be spotted is between 70 and 90 km during the southern summer (Ls = 240–300°; perihelion season), approaching the transition between the middle and upper atmosphere. In this season, years without a global dust storm (GDS) show a significant moistening of the upper atmosphere (∼100 ppmv) in the southern hemisphere, confirming a seasonal impact on the hydrogen escape rate. The two observed GDS, in MY28 and MY34, show a substantial disparity in water vapor response. The storm in MY28, which coincides with the southern summer solstice, creates the largest excess of water in both hemispheres at >80 km. This climatology of water vapor will supply a robust statistical basis to address the long‐term escape processes of water from Mars.

中文翻译：

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火星快车上的SPICAM对火星上水汽垂直分布进行多年监测

长期以来，水蒸气的高度分布一直是火星上水蒸气观测数据集的缺失部分。在这项研究中，我们基于SPICAM / Mars Express掩星测量结果，首次进行了从0到100 km高度范围内水汽剖面的多年期调查。在顶栖季节，在整个火星年中，水一直被限制在40-60公里以下。在南方夏季，可以发现水蒸气的最高高度在70至90公里之间（Ls = 240–300°；近日点季节），接近中高层大气之间的过渡。在这个季节，没有全球沙尘暴（GDS）的年份显示出南半球的高层大气显着增湿（〜100 ppmv），证实了对氢逸出率的季节性影响。在MY28和MY34中观察到的两个GDS在水蒸气响应方面显示出很大的差异。MY28的风暴与南夏至相吻合，在两个半球中> 80 km处造成最大的水过多。水蒸气的这种气候学将为解决火星中水的长期逸出过程提供有力的统计依据。