Ground-based remote sensing measurements of CO2 and CH4 using the moon as light source during the polar night

在过去几年中，人们开发了测量技术，利用近红外光谱区的地面太阳吸收遥感光谱测定法，以足够的精度测量大气CO2和CH4总柱。这些观测在全球范围内由总柱碳观测网络（TCCON）组织。这些观测是为了卫星验证而启动的，因为它们以与卫星类似的方式对大气进行采样。然而，测量本身已被发现是非常有价值的调查源和汇的微量气体，因为地面总柱数据的解释依赖于在较小程度上的假设在大气中的垂直混合相比，地面原位数据。我们在北极高纬度的斯匹次卑尔根群岛（79°N）进行了这样的观测。然而，在10月至3月中旬的极夜期间，由于太阳在地平线以下，因此无法进行观测。由于北方高纬度地区CO2的季节性循环最大，冬季总柱数据的缺乏限制了我们对碳收支的理解。在这个项目中，我们计划修改测量和分析技术，以测量在近红外线的总柱CO2和CH4使用月球作为光源在极夜。这将使我们能够在满月前后±3天进行观测，从而在整个极夜获得大约三个满月周期的数据。这使得能够测量北极高纬度地区CO2和CH4总气柱测量的完整季节性周期，这是迄今为止所不知道的。最后，将把整套数据与该场址现有的现场地面数据进行比较，并将现场和总柱的两套数据与适当的模型进行比较。

Throughout the last years measurement techniques have been developed to measure total columns of atmospheric CO2 and CH4 with sufficient precision using the ground-based solar absorption remote sensing spectrometry in the near-infrared spectral region. These observations are internationally organized in the Total Column Carbon Observing Network (TCCON). These observations have been initiated for the satellite validation, because they sample the atmosphere in a similar way as satellites. However, the measurements itself have been found extremely valuable to investigate the sources and sinks of the trace gases, because the interpretation of the ground-based total column data depend to a less extent on assumptions on the vertical mixing in the atmosphere compared to surface in-situ data. We perform such observations at our site in the high Arctic on Spitsbergen (79°N). However, during the polar night from October until mid March no observations can be performed, because the sun is below the horizon. Since the seasonal cycle of CO2 is largest in the high northern latitudes the lack of total column data for the winter period limits our understanding of the carbon budget. Within this project we plan to modify the measurement and analysis technique to measure the total columns of CO2 and CH4 in the near-infrared using the moon as light source during the polar night. This will allow us to perform observations on ±3 days around full moon, and thus, obtain data throughout the polar night for about three full moon periods. This allows measuring the complete seasonal cycle of total column measurements of CO2 and CH4 in the high Arctic, which is not known so far. Finally, the whole set of data will be compared to the existing in-situ surface data at that site and both data sets, in-situ and total column, will be compared with appropriate models.