Analysis of reactive bromine production and ozone depletion in the Arctic boundary layer using 3-D simulations with GEM-AQ: Inference from synoptic-scale patterns
Analysis of reactive bromine production and ozone depletion in the Arctic boundary layer using 3-D simulations with GEM-AQ: Inference from synoptic-scale patterns
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DOI：
10.5194/acp-11-3949-2011
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发表时间：
2011-04
影响因子：
6.3
通讯作者：
K. Toyota;J. McConnell;A. Lupu;L. Neary;C. McLinden;A. Richter;R. Kwok;K. Semeniuk;J. Kaminski;S. Gong;J. Jarosz;M. Chipperfield;C. Sioris
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文献类型：
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作者：
K. Toyota;J. McConnell;A. Lupu;L. Neary;C. McLinden;A. Richter;R. Kwok;K. Semeniuk;J. Kaminski;S. Gong;J. Jarosz;M. Chipperfield;C. Sioris
抽象。高溴水平和地面臭氧消耗在春季北极的发作模拟了一个在线的空气质量模型，GEM-AQ，气相和非均相反应的无机溴物种和一个简单的计划，空气积雪化学相互作用实施这项研究。海冰上的积雪被认为是溴的唯一来源，并能够通过空气积雪相互作用将相对稳定的溴物种转化为对光不稳定的Br 2。2001年4月，在北极地区进行了一系列水平分辨率约为100 km×100 km的敏感性模型试验，以深入了解温度和海冰年龄（第一年，FY与多年，MY）对活性溴释放到大气中的影响。模型模拟捕捉到了在北极高地观测站观测到的地面臭氧混合比的大部分时间变化，以及根据卫星观测估计的BrO柱量增加的地区（“BrO云”）的天气尺度演变。模拟的“溴云”是在适度更好的协议与卫星测量时，风云海冰被认为是更有效地释放活性溴到大气中比我的海冰。本研究中使用的沿海站的表面臭氧数据不足以明确评估FY海冰和MY海冰作为溴源之间的差异。研究结果表明，北极春季海冰上的雪中普遍存在活性溴的释放，而释放的时间和位置在很大程度上受气象因素的控制。这似乎是一个快速的平流和增强湍流扩散与强大的边界层风驱动臭氧的运输和分散到近表面的空气在海冰，增加了溴化物（Br −）的氧化率在表面雪。此外，如果北极边界层的大部分活性溴确实是由表层积雪提供的，那么在零下10摄氏度的温度下，它似乎能够释放活性溴，特别是在北冰洋中部和东部的海冰上。动态引起的溴柱变化在最低平流层出现干扰使用卫星溴柱测量解释溴在对流层下部的变化，但可能不会完全模糊的程度“溴云”，起源于高北极的表面雪/冰源溴。溴化合物的模拟空气-表面交换的预算分析表明，“溴爆炸”发生在间隙空气的积雪和/或加速由风吹雪在环境空气中，这两个都没有明确表示在我们的简单模型的表面上的非均相反应，但可以近似由一个参数调整的Br 2的产量从触发器。
Abstract. Episodes of high bromine levels and surface ozone depletion in the springtime Arctic are simulated by an online air-quality model, GEM-AQ, with gas-phase and heterogeneous reactions of inorganic bromine species and a simple scheme of air-snowpack chemical interactions implemented for this study. Snowpack on sea ice is assumed to be the only source of bromine to the atmosphere and to be capable of converting relatively stable bromine species to photolabile Br 2 via air-snowpack interactions. A set of sensitivity model runs are performed for April 2001 at a horizontal resolution of approximately 100 km×100 km in the Arctic, to provide insights into the effects of temperature and the age (first-year, FY, versus multi-year, MY) of sea ice on the release of reactive bromine to the atmosphere. The model simulations capture much of the temporal variations in surface ozone mixing ratios as observed at stations in the high Arctic and the synoptic-scale evolution of areas with enhanced BrO column amount ("BrO clouds") as estimated from satellite observations. The simulated "BrO clouds" are in modestly better agreement with the satellite measurements when the FY sea ice is assumed to be more efficient at releasing reactive bromine to the atmosphere than on the MY sea ice. Surface ozone data from coastal stations used in this study are not sufficient to evaluate unambiguously the difference between the FY sea ice and the MY sea ice as a source of bromine. The results strongly suggest that reactive bromine is released ubiquitously from the snow on the sea ice during the Arctic spring while the timing and location of the bromine release are largely controlled by meteorological factors. It appears that a rapid advection and an enhanced turbulent diffusion associated with strong boundary-layer winds drive transport and dispersion of ozone to the near-surface air over the sea ice, increasing the oxidation rate of bromide (Br − ) in the surface snow. Also, if indeed the surface snowpack does supply most of the reactive bromine in the Arctic boundary layer, it appears to be capable of releasing reactive bromine at temperatures as high as −10 °C, particularly on the sea ice in the central and eastern Arctic Ocean. Dynamically-induced BrO column variability in the lowermost stratosphere appears to interfere with the use of satellite BrO column measurements for interpreting BrO variability in the lower troposphere but probably not to the extent of totally obscuring "BrO clouds" that originate from the surface snow/ice source of bromine in the high Arctic. A budget analysis of the simulated air-surface exchange of bromine compounds suggests that a "bromine explosion" occurs in the interstitial air of the snowpack and/or is accelerated by heterogeneous reactions on the surface of wind-blown snow in ambient air, both of which are not represented explicitly in our simple model but could have been approximated by a parameter adjustment for the yield of Br 2 from the trigger.