Lower atmosphere variations in the martian water vapour and hydrogen abundance during the late southern summer regional-scale dust storm from $L_{\mathrm{S}}$ = 326.1°–333.5° Mars Year 34 (18th-31st January 2019) and their associated effect on hydrogen escape are investigated using a multi-spacecraft assimilation of atmospheric retrievals into a Martian global circulation model. The dusty conditions led to an elevation of the hygropause and associated increase in middle atmosphere hydrogen at the peak of the dust storm, which was particularly intense in Mars Year 34. This response has an important effect on water loss during this time period, quantification of which can provide a more robust calculation of the integrated loss of water through time on Mars and better insight to planetary evolution. The influx of water vapour to higher altitudes led to an associated increase in hydrogen through photolysis of water vapour and a hydrogen escape rate of around $1.0\times {10}^9$ cm⁻² s⁻¹, meaning the late southern summer regional-scale dust storm in Mars Year 34 enhanced water loss rates on Mars to levels observed during global-scale dust storms. The water loss rate during the late southern summer regional-scale dust storm, also known as a C storm, led to around 15% of the total annual water loss during only 5% of the year and was at least three times stronger than the much less dusty C storm event in Mars Year 30. These results demonstrate that interannual variations in the strength of the late southern summer regional-scale dust storm must be considered when calculating the integrated loss of water on Mars, an important quantity to constrain in relation to the potential habitability of Mars.

南部夏末区域尺度沙尘暴期间火星水蒸气和氢丰度的较低大气变化 ${升}_{\mathrm{秒}}$= 326.1°–333.5° 火星第 34 年（2019 年 1 月 18 日至 31 日）及其对氢逃逸的相关影响，使用多航天器将大气反演同化到火星全球环流模型中进行研究。沙尘暴的高峰期，沙尘暴的高峰期水层顶升高和相关的中层大气氢气增加，这在火星第 34年尤为强烈。这种反应对这段时间的水分流失有重要影响，量化它可以更可靠地计算火星上随时间推移的综合水损失，并更好地了解行星演化。水蒸气涌入更高的高度，通过水蒸气的光解作用导致氢气的相关增加，氢气逸出率约为$1.0\times {10}^9$cm ^-2  s ^-1，这意味着火星第 34年的南部夏末区域尺度沙尘暴将火星上的水分流失率提高到全球尺度沙尘暴期间观察到的水平。南部夏末区域尺度沙尘暴（也称为 C 型风暴）期间的失水率仅占全年总失水量的 15% 左右，而一年中仅有 5%火星 30年沙尘较少的 C 风暴事件。这些结果表明，在计算火星上的综合水损失时，必须考虑南部夏末区域尺度沙尘暴强度的年际变化，这是一个重要的量，以限制与火星的潜在宜居性。