A subset of more than 100,000 nadir measurements covering more than 7 Martian years (MY 26–MY 33) recorded in the thermal part of the Short Wavelength Channel (SWC) from the Planetary Fourier Spectrometer (PFS) on board Mars Express is exploited to investigate the global distribution and the seasonal cycle of carbon monoxide (CO) on Mars. The retrieval of CO vertical profiles is successfully achieved using a methodology based on the optimal estimation but the low information content is such that we mainly discuss the variability in CO in terms of integrated columns (from the surface to 24 km) or the associated column‐averaged mixing ratio. We find a strong seasonality in CO, especially at mid and high‐latitudes, which confirms earlier work and the current knowledge of the CO₂ condensation/sublimation cycles, as implemented for instance in the Global Environmental Multiscale (GEM) general circulation model for Mars, that we use as a basis for comparison. We report a general consistency between model and observation, with a tendency of the latter to provide lower CO volume mixing ratios (VMRs), except at low latitudes. The spatial distribution of the CO column‐averaged VMR is obtained on a seasonal basis and investigated in terms of large‐scale patterns but also local peculiarities. Finally, we show that the retrieved profiles systematically present strong CO vertical gradients close to the surface in mid‐ and equatorial latitudes, likely related to the vertical sensitivity of PFS rather than real near‐surface CO enrichment.

中文翻译：

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从PFS / MEX观测资料看，火星大气中一氧化碳（CO）的季节性和空间变异性

利用火星快车上行星傅里叶光谱仪（PFS）记录的短波长通道（SWC）的热部分中记录的超过100,000个最低点的子集，覆盖了超过7个火星年（MY 26–MY 33）。火星上一氧化碳（CO）的全球分布和季节周期。使用基于最佳估计的方法成功地实现了CO垂直剖面的检索，但是信息含量低，因此我们主要讨论的是CO的变化性，是从集成柱（从地面到24 km）还是相关柱平均混合比。我们发现CO的季节性很强，特别是在中高纬度地区，这证实了早期的工作以及对CO ₂的当前了解凝结/升华循环，例如在全球环境多尺度（GEM）火星通用循环模型中实施的时间，我们以此为基础进行比较。我们报告了模型和观测值之间的总体一致性，除了低纬度地区，后者倾向于提供较低的CO体积混合比（VMRs）。CO柱平均VMR的空间分布是在季节性基础上获得的，并针对大型模式以及局部特征进行了调查。最后，我们表明，所获取的剖面系统地在中纬度和赤道纬度附近系统呈现强CO垂直梯度，这很可能与PFS的垂直敏感性有关，而不是与实际近地表CO富集有关。