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Investigation into approaches to reduce excessive vertical transport over complex terrain in a regional photochemical grid model

机译：在区域光化学网格模型中减少复杂地形上过多垂直运输的方法研究

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摘要

Past photochemical modeling of the western United States (US) using the Comprehensive Air quality Model with extensions (CAMx) and the Community Multiscale Air Quality (CMAQ) model has resulted in large springtime ozone over predictions in the complex high-elevation terrain of the western United States (US). Comparisons against rural measurement data have shown that both models over predicted ozone levels by 20 ppb or more. A systematic investigation using CAMx revealed that excessive vertical transport in mountainous terrain draws down upper tropospheric ozone introduced by the lateral boundary conditions (developed by a global chemistry model), which can routinely exceed 1 ppm near the tropopause. This is not an unreasonable concentration at such altitudes during the spring, and there is observational evidence that stratospheric ozone intrusions result in occasional large ground-level concentrations in the western US, but not at the frequency and intensity simulated by the CAMx and CMAQ models. Past versions of CAMx and CMAQ possess similar algorithms to diagnose vertical velocity, and similar first-order accurate vertical advection algorithms. These similarities, in conjunction with poor vertical resolution of the upper troposphere, have resulted in similar ozone performance issues. Numerous approaches were explored with CAMx in an attempt to externally reduce the rates of vertical transport over complex terrain. Ultimately, we formulated and tested a new vertical advection methodology that included improvements to how vertical velocities are determined and introduced a second-order accurate advection solver technique. Together these improvements proved to yield the most successful results in reducing upper tropospheric ozone transport to the surface. CAMx was then run to simulate ozone throughout the western US for a full year to evaluate the effects of the new vertical transport algorithm on model performance. Ozone performance improvements exceeded those achieved through the application of arbitrary reductions in the upper tropospheric/stratospheric lateral boundary conditions.
机译：过去使用扩展的综合空气质量模型（CAMx）和社区多尺度空气质量（CMAQ）模型对美国西部（US）进行的光化学建模已导致在春季西部复杂的高海拔地形中超出预测的大量春季臭氧美国（US）。与农村测量数据的比较表明，这两种模型都将臭氧水平的预测值提高了20 ppb或更高。使用CAMx进行的系统调查显示，山区地形中过多的垂直运输会吸收由侧向边界条件（由全球化学模型开发）引入的对流层上方的臭氧，通常在对流层顶附近超过1 ppm。在春季这样的高度，这并不是一个不合理的浓度，并且有观察证据表明，平流层臭氧的入侵偶尔会导致美国西部的地面浓度较高，但不是CAMx和CMAQ模型所模拟的频率和强度。过去的CAMx和CMAQ版本具有类似的算法来诊断垂直速度，并且具有类似的一阶精确垂直对流算法。这些相似之处，加上对流层上层垂直分辨率差，导致了类似的臭氧性能问题。 CAMx探索了许多方法，以尝试从外部降低复杂地形上的垂直传输速率。最终，我们制定并测试了一种新的垂直对流方法，其中包括改进了确定垂直速度的方式，并引入了二阶精确对流求解器技术。事实证明，这些改进在减少对流层上空臭氧向地面的输送方面取得了最成功的结果。然后运行CAMx来模拟整个美国西部的臭氧整整一年，以评估新的垂直传输算法对模型性能的影响。臭氧性能的改善超过了通过对流层/平流层上边界条件任意降低而实现的改善。

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  • 来源
    《Atmospheric environment》 |2011年第39期|p.7341-7351|共11页
  • 作者

    Christopher Emery; Ed Tai; Greg Yarwood; Ralph Morris;

  • 作者单位

    ENVIRON international Corporation, 773 San Marin Drive, Suite 2115, Novato, CA 94998, USA;

    ENVIRON international Corporation, 773 San Marin Drive, Suite 2115, Novato, CA 94998, USA;

    ENVIRON international Corporation, 773 San Marin Drive, Suite 2115, Novato, CA 94998, USA;

    ENVIRON international Corporation, 773 San Marin Drive, Suite 2115, Novato, CA 94998, USA;

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  • 正文语种 eng
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  • 关键词

    CAMx; CMAQ; ozone transport; vertical advection;

    机译：CAMx;CMAQ;臭氧运输;垂直对流;

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