Abstract. Errors in assumed pollutant emission characteristics can significantly impact the magnitude of the estimated emissions constrained by instantaneous observations obtained with airborne or remote sensing instruments, especially on the local scale. Realistic emissions from individual point sources are a valuable input for numerical models, as by minimizing the errors stemming from inaccurate emissions, they could allow a better characterization of errors caused by transport mechanisms. Here we provide a detailed description of factors influencing the coal-mine methane emission variability, based on high-frequency (up to hourly) temporal data obtained from seven coal mines from the Upper Silesian Coal Basin during CoMet 1.0 (Carbon dioxide and Methane) mission which took place from May 14 to June 13, 2018. The knowledge of these factors for the particular ventilation shaft is essential for linking the observations achieved during the CoMet 1.0 with models, as most of the publicly available data in the bottom-up worldwide inventories provide annual emissions only. The methane concentrations in examined shafts ranged from 0.10 % to 0.55 % during the study period and were subject to a significant variation on a day-to-day basis due to the changing scope of mining works performed underground. The yearly methane average emission rate calculated based on temporal data of the analyzed subset of mines was of the order of 142.68 kt yr^-1, an estimate lower by 27 % than the oficially published WUG (State Mining Authority) data and 36 % than reported to E-PRTR (European Pollutant Release and Transfer Register). Additionally, we found that emissions from individual coal mine facilities were over- or underestimated by between 4 % to 60 %, compared to E-PRTR, when short-term records were analysed. We show that the observed discrepancies between annual emissions based on temporal data and public inventories result from, firstly, the incorrect assumption that the methane concentrations in the time-invariant, secondly, from the methodology of measurements, and lastly, from frequency and timing of measurements. From the emission monitoring perspective, we recommend usage of a standardized emission measurement system for all coal mines, similar to the the SMP-NT/A methane fire teletransmission monitoring system (which most coal mines are equipped with). Such a system could, allow for gas flow quantification, necessary for accurate and precise estimations of methane emissions at high temporal resolution. Using this system will also reduce the emission uncertainty due to factors like frequency and timing of measurements. In addition, separating the emissions from individual ventilation shafts and methane drainage stations would be beneficial in closing the gap between bottom-up and top-down approaches for coal mine emissions, as the intermittent releases of unutilized methane from the drainage stations is currently not considered when constructing regional methane budgets.

中文翻译：

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影响上西里西亚煤矿大气甲烷排放时间变化的因素：来自 CoMet 任务的案例研究

摘要。假设的污染物排放特征的误差会显着影响估计排放量的大小，这些排放量受使用机载或遥感仪器获得的瞬时观测值的限制，尤其是在当地尺度上。来自单个点源的实际排放是数值模型的宝贵输入，因为通过最小化不准确排放引起的误差，它们可以更好地表征由传输机制引起的误差。在这里，我们根据在 CoMet 1.0（二氧化碳和甲烷）任务期间从上西里西亚煤盆地的七个煤矿获得的高频（最多每小时）时间数据，详细描述了影响煤矿甲烷排放变化的因素时间为 2018 年 5 月 14 日至 6 月 13 日。了解特定通风井的这些因素对于将 CoMet 1.0 期间获得的观测结果与模型联系起来至关重要，因为自下而上的全球清单中的大多数公开数据仅提供年度排放量。在研究期间，被检查竖井中的甲烷浓度范围为 0.10% 至 0.55%，并且由于地下采矿工程范围的变化，每天都会发生显着变化。根据所分析矿山子集的时间数据计算的年平均甲烷排放量约为 142.68 kt yr 在研究期间，被检查竖井中的甲烷浓度范围为 0.10% 至 0.55%，并且由于地下采矿工程范围的变化，每天都会发生显着变化。根据所分析矿山子集的时间数据计算的年平均甲烷排放量约为 142.68 kt yr 在研究期间，被检查竖井中的甲烷浓度范围为 0.10% 至 0.55%，并且由于地下采矿工程范围的变化，每天都会发生显着变化。根据所分析矿山子集的时间数据计算的年平均甲烷排放量约为 142.68 kt yr^-1，估计比官方公布的 WUG（国家矿业局）数据低 27%，比 E-PRTR（欧洲污染物释放和转移登记册）报告的数据低 36%。此外，我们发现，在分析短期记录时，与 E-PRTR 相比，单个煤矿设施的排放量被高估或低估了 4% 到 60%。我们表明，基于时间数据和公共清单的年排放量之间观察到的差异首先是由于不正确假设甲烷浓度不随时间变化，其次是测量方法，最后是频率和时间测量。从排放监测的角度来看，我们建议对所有煤矿使用标准化的排放测量系统，类似于 SMP-NT/A 甲烷火灾远传监控系统（大多数煤矿都配备）。这样的系统可以允许气体流量量化，这对于以高时间分辨率准确和精确地估计甲烷排放量是必要的。使用该系统还将减少由于测量频率和时间等因素造成的排放不确定性。此外，将各个通风井和瓦斯排放站的排放分开将有利于缩小煤矿排放自下而上和自上而下方法之间的差距，因为目前未考虑排放站未利用甲烷的间歇性排放在构建区域甲烷预算时。允许气体流量量化，这对于以高时间分辨率准确和精确地估计甲烷排放量是必要的。使用该系统还将减少由于测量频率和时间等因素造成的排放不确定性。此外，将各个通风井和瓦斯排放站的排放分开将有利于缩小煤矿排放自下而上和自上而下方法之间的差距，因为目前未考虑排放站未利用甲烷的间歇性排放在构建区域甲烷预算时。允许气体流量量化，这对于以高时间分辨率准确和精确地估计甲烷排放量是必要的。使用该系统还将减少由于测量频率和时间等因素造成的排放不确定性。此外，将各个通风井和瓦斯排放站的排放分开将有利于缩小煤矿排放自下而上和自上而下方法之间的差距，因为目前未考虑排放站未利用甲烷的间歇性排放在构建区域甲烷预算时。