Differential column measurements using compact solar-tracking spectrometers
Differential column measurements using compact solar-tracking spectrometers
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DOI：
10.5194/acp-16-8479-2016
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发表时间：
2016-01-01
影响因子：
6.3
通讯作者：
Wofsy, Steven C.
中科院分区：
文献类型：
--
作者：
Chen, Jia;Viatte, Camille;Wofsy, Steven C.
我们演示了使用紧凑的太阳跟踪傅里叶变换光谱仪（布鲁克EM 27/SUN）的差分测量的列平均干空气中的甲烷和二氧化碳的摩尔分数在城市地区。使用Allan方差分析，我们表明，差分柱测量的精度为0.01%的X-CO 2和X-CH 4的最佳积分时间为10分钟，相应的Allan偏差为0.04 ppm和0.2 ppb，分别。该传感器系统在整个大陆重新安置后，随着时间的推移非常稳定。我们报告测试的差分柱测量，其敏感性的排放源，通过测量跨奶牛场的奇诺地区，加州的顺风减去逆风柱差Δ X-CH 4，并使用的数据来验证文献中报道的排放量。比率的空间列差异Δ X-CH 4/Δ X-CO2观察整个帕萨迪纳在洛杉矶盆地，表明值与区域排放比从文献中。我们的精确，快速的测量使我们能够确定显着的短期变化（5-10分钟）的X-CO2和X-CH 4，并表明他们代表大气现象。总体而言，这项研究有助于建立一系列新的应用紧凑型太阳观察傅里叶变换光谱仪。通过精确测量本地和区域污染源的综合柱量的微小差异，我们直接观察到由于干扰场所排放的影响而导致的大气质量负荷。源强度的推断比仅使用表面浓度的反演建模更直接，并且较少受到与小尺度传输现象相关的误差的影响。
We demonstrate the use of compact solar-tracking Fourier transform spectrometers (Bruker EM27/SUN) for differential measurements of the column-averaged dry-air mole fractions of CH4 and CO2 within urban areas. Using Allan variance analysis, we show that the differential column measurement has a precision of 0.01% for X-CO2 and X-CH4 with an optimum integration time of 10 min, corresponding to Allan deviations of 0.04 ppm and 0.2 ppb, respectively. The sensor system is very stable over time and after relocation across the continent. We report tests of the differential column measurement, and its sensitivity to emission sources, by measuring the downwind-minus-upwind column difference Delta X-CH4 across dairy farms in the Chino area, California, and using the data to verify emissions reported in the literature. Ratios of spatial column differences Delta X-CH4/Delta X-CO2 were observed across Pasadena within the Los Angeles basin, indicating values consistent with regional emission ratios from the literature. Our precise, rapid measurements allow us to determine significant short-term variations (5-10 min) of X-CO2 and X-CH4 and to show that they represent atmospheric phenomena.Overall, this study helps establish a range of new applications for compact solar-viewing Fourier transform spectrometers. By accurately measuring the small differences in integrated column amounts across local and regional sources, we directly observe the mass loading of the atmosphere due to the influence of emissions in the intervening locale. The inference of the source strength is much more direct than in-version modeling using only surface concentrations and less subject to errors associated with small-scale transport phenomena.