光腔衰荡光谱法(CRDS)和色谱法(GC)均可用于甲烷(CH4)和一氧化碳(CO)的在线观测.金沙大气本底站建立了基于 CRDS和 GC的平行观测系统,对大气中的 CH4 和 CO进行了长达一年半的在线观测试验,对二者获取的数据进行了对比分析.结果表明:CRDS对 CH4 和 CO 观测的长期稳定性和准确性明显优于 GC;CRDS和 GC 获取 CH4 的系统偏差满足世界气象组织全球大气观测计划(WMO/GAW)的兼容性指标要求,获取 CO 的系统偏差不满足兼容性指标要求;CRDS和 GC获取 CH4 的日变化曲线基本重合,均呈现双峰形态,获取 CO 的日变化曲线也基本重合,但变化特征均不明显;CRDS和 GC获取 CH4 的季节变化曲线基本重合,7-8 月最低,与北半球变化趋势吻合,获取的 CO 季节变化曲线趋势上基本一致,在夏季 7 月出现谷值.
Comparison of Online Monitoring Results of Atmospheric CH4 and CO Using CRDS and GC Methods
The cavity ring-down spectroscopy(CRDS)and gas chromatography(GC)can both be used for the online observation of methane(CH4)and carbon monoxide(CO).A parallel observation system based on CRDS and GC was established in Jinsha atmospheric background station,and the online observation experiment of CH4 and CO in the atmosphere was carried out for one and a half years,and the data obtained from both methods were compared and analyzed.The results showed that the long-term stability and accuracy of CH4 and CO observations with CRDS were significantly better than GC;the systematic biases of CH4 obtained by CRDS and GC could meet the compatibility requirements of the World Meteorological Organization Global Atmosphere Watch(WMO/GAW),while the systematic bias of CO obtained could not meet the compatibility requirements;the daily variation curves of CH4 obtained by CRDS and GC were basically coincident,showing a bimodal pattern,while the daily variation curves of CO also largely overlap but with less distinct characteristics;the seasonal variation curves of CH4 obtained by CRDS and GC were basically the same,with the lowest levels in July-August,matching the trend in the Northern Hemisphere,and the seasonal variation curves of CO showed a similar trend,with a valley occurring in July during summer.
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