We present a local-scale atmospheric inversion framework to estimate the location and rate of methane (CH₄) and carbon dioxide (CO₂) releases from point sources. It relies on mobile near-ground atmospheric CH₄ and CO₂ mole fraction measurements across the corresponding atmospheric plumes downwind of these sources, on high-frequency meteorological measurements, and on a Gaussian plume dispersion model. The framework exploits the scatter of the positions of the individual plume cross sections, the integrals of the gas mole fractions above the background within these plume cross sections, and the variations of these integrals from one cross section to the other to infer the position and rate of the releases. It has been developed and applied to provide estimates of brief controlled CH₄ and CO₂ point source releases during a 1-week campaign in October 2018 at the TOTAL experimental platform TADI in Lacq, France. These releases typically lasted 4 to 8 min and covered a wide range of rates (0.3 to 200 g CH₄/s and 0.2 to 150 g CO₂/s) to test the capability of atmospheric monitoring systems to react fast to emergency situations in industrial facilities. It also allowed testing of their capability to provide precise emission estimates for the application of climate change mitigation strategies. However, the low and highly varying wind conditions during the releases added difficulties to the challenge of characterizing the atmospheric transport over the very short duration of the releases. We present our series of CH₄ and CO₂ mole fraction measurements using instruments on board a car that drove along roads ∼50 to 150 m downwind of the 40 m × 60 m area for controlled releases along with the estimates of the release locations and rates. The comparisons of these results to the actual position and rate of the controlled releases indicate ∼10 %–40 % average errors (depending on the inversion configuration or on the series of tests) in the estimates of the release rates and ∼30–40 m errors in the estimates of the release locations. These results are shown to be promising, especially since better results could be expected for longer releases and under meteorological conditions more favorable to local-scale dispersion modeling. However, the analysis also highlights the need for methodological improvements to increase the skill for estimating the source locations.

中文翻译：

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点源短暂 CH4 和 CO2 释放的位置和速率的移动大气测量和局部尺度逆估计

我们提出了一个局部尺度的大气反演框架来估计点源释放甲烷 (CH ₄ ) 和二氧化碳 (CO ₂ )的位置和速率。它依赖于移动的近地大气 CH ₄和 CO ₂在这些源下风处的相应大气羽流中的摩尔分数测量、高频气象测量和高斯羽流扩散模型。该框架利用单个羽流横截面位置的分散性、这些羽流横截面内高于背景的气体摩尔分数的积分，以及这些积分从一个横截面到另一个横截面的变化来推断位置和速率的版本。它已被开发并应用于提供短暂受控 CH ₄和 CO _{2 的}估计值2018 年 10 月在法国拉克的 TOTAL 实验平台 TADI 进行的为期 1 周的活动中发布了点源。这些释放通常持续 4 到 8 分钟，涵盖了广泛的速率范围（0.3 到 200 克 CH ₄ /s 和 0.2 到 150 克 CO ₂ /s），以测试大气监测系统对工业紧急情况做出快速反应的能力设施。它还允许测试他们为减缓气候变化战略的应用提供精确排放估算的能力。然而，释放过程中的低风况和高度变化的风条件增加了在非常短的释放持续时间内表征大气传输的挑战的难度。我们展示了我们的 CH ₄和 CO ₂系列使用在 40 m ×  60 m 区域下风向约50至 150 m行驶的汽车上的仪器进行摩尔分数测量， 以 进行受控释放以及释放位置和速率的估计。这些结果的控制释放的实际位置和速度的比较指示〜10  ％-40％的平均误差（取决于反转配置，或者在一系列的测试）中释放率和估计约30– 40 m 的释放位置估计误差。这些结果被证明是有希望的，特别是因为可以预期更长的释放和在更利于局部尺度扩散建模的气象条件下获得更好的结果。然而，分析还强调需要改进方法以提高估计源位置的技能。