Tall Tower Vertical Profiles and Diurnal Trends of Ammonia in the Colorado Front Range
Tall Tower Vertical Profiles and Diurnal Trends of Ammonia in the Colorado Front Range
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DOI：
10.1002/2017jd026534
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发表时间：
2017-11
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通讯作者：
A. Tevlin;Yi Li;Jeffrey Collett;E. McDuffie;Emily V. Fischer;J. Murphy
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作者：
A. Tevlin;Yi Li;Jeffrey Collett;E. McDuffie;Emily V. Fischer;J. Murphy
2014年夏天，作为Front Range空气污染和光化学Éxperiment项目的一部分，在博尔德大气观测塔的一个可移动的载体上测量了地表和地面以上280米之间的氨（NH3）混合比。运动中位数混合比为3.3 ppb，范围从低于检测限到192 ppb。垂直剖面中位数显示，朝向地表的NH3混合比在白天增加6.7 ppb(89%)，在夜间增加3.9 ppb（141%）。与总体上升趋势相反，个别剖面在最低10 m处NH3呈下降趋势。这表明，根据地表和平流气流中NH3的相对数量，局部地表能够充当源或汇。我们进一步使用这些数据集来研究NH3的日变化模式作为地表以上高度的函数。在海拔较高的地区（100±5和280±5 m）， NH3混合比在当地时间9:00 - 16:00之间逐渐达到最大值，可能受源区域变化的驱动。在海拔较低的地区（10±5米），白天的最大值在当地时间7点左右开始较早，随后在当地时间9点时急剧增加。在这个高度，我们还观察到夜间NH3混合比率的峰值，可能是由于在较浅的夜间边界层中捕获了排放的NH3。
Ammonia (NH3) mixing ratios were measured between the surface and 280 m aboveground level from a moveable carriage at the Boulder Atmospheric Observatory tower in summer 2014 as part of the Front Range Air Pollution and Photochemistry Éxperiment. The campaign median mixing ratio was 3.3 ppb, ranging from below detection limits to 192 ppb. Median vertical profiles show an overall increase in NH3 mixing ratios toward the surface of 6.7 ppb (89%) during the day and 3.9 ppb (141%) at night. In contrast to the overall increasing trend, some individual profiles show decreasing NH3 in the lowest 10 m. This suggests that the local surface is capable of acting as either a source or a sink, depending on the relative amounts of NH3 at the surface, and in advected air parcels. We further use this data set to investigate the variation in diurnal patterns of NH3 as a function of height above the surface. At higher altitudes (100 ± 5 and 280 ± 5 m), NH3 mixing ratios reach a gradual maximum during the day between 9:00 and 16:00 local time, likely driven by changes in source region. At lower altitudes (10 ± 5 m), the daytime maximum begins earlier at about 7:00 local time, followed by a sharper increase at 9:00 local time. At this height we also observe a peak in NH3 mixing ratios during the night, likely driven by the trapping of emitted NH3 within the shallower nocturnal boundary layer.