A novel downscaling technique for the linkage of global and regional air quality modeling
A novel downscaling technique for the linkage of global and regional air quality modeling
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DOI：
10.5194/acp-9-9169-2009
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发表时间：
2009-01-01
影响因子：
6.3
通讯作者：
Fu, J. S.
中科院分区：
文献类型：
--
作者：
Lam, Y. F.;Fu, J. S.
最近，降尺度全球大气模型输出（GCTM）的USEPA社区多尺度空气质量（CMAQ）初始（IC）和边界条件（BC）已经成为现实，因为计算技术的快速增长，使全球模拟在合理的时间内完成。传统的由剖面数据生成IC/BC的方法由于网格边界层上有限的水平和垂直变化而失去了它的拥护者。从理论上讲，高质量的GCTM IC/BC应该在CMAQ中产生更好的结果。不幸的是，一些研究人员已经发现，GCTM IC/BC的输出不一定比轮廓IC/BC更好，这是由于GCTM IC/BC中的O-3的过量运输。在本文中，我们打算调查的影响，使用轮廓IC/BC和全球大气模式数据。此外，我们提出了一种新的方法来解决现有的问题，在这项研究中，我们利用GEOS-Chem模式的输出来产生2002年的时变和分层的IC/BC，并在降尺度过程中实施对流层顶确定算法（即，基于化学（O-3）对流层顶定义）。最后，通过对已实现的对流层顶方法和剖面IC/BC方法的比较，说明了考虑对流层顶的方法的改进。据观察，不使用对流层顶的信息在降尺度过程中，不切实际的O-3浓度在IC/BC的上层创建。这一现象导致了CMAQ中表面O-3的过度预测。此外，过度预测的量很大程度上受温度和纬度位置的研究领域。随着算法的实施，我们已经成功地解决了全球和区域化学模型之间的垂直层结构的不兼容性问题，以获得更好的表面O-3的预测比配置文件IC/BC的夏季和冬季条件。同时，它改善了CMAQ输出的垂直O-3分布。强烈建议在使用对流层区域模式的任何双向耦合的全球和区域模式中纳入对流层顶信息，以解决全球和区域模式之间存在的垂直不兼容问题。
Recently, downscaling global atmospheric model outputs (GCTM) for the USEPA Community Multiscale Air Quality (CMAQ) Initial (IC) and Boundary Conditions (BC) have become practical because of the rapid growth of computational technologies that allow global simulations to be completed within a reasonable time. The traditional method of generating IC/BC by profile data has lost its advocates due to the weakness of the limited horizontal and vertical variations found on the gridded boundary layers. Theoretically, high quality GCTM IC/BC should yield a better result in CMAQ. Unfortunately, several researchers have found that the outputs from GCTM IC/BC are not necessarily better than profile IC/BC due to the excessive transport of O-3 aloft in GCTM IC/BC. In this paper, we intend to investigate the effects of using profile IC/BC and global atmospheric model data. In addition, we are suggesting a novel approach to resolve the existing issue in downscaling.In the study, we utilized the GEOS-Chem model outputs to generate time-varied and layer-varied IC/BC for year 2002 with the implementation of tropopause determining algorithm in the downscaling process (i.e., based on chemical (O-3) tropopause definition). The comparison between the implemented tropopause approach and the profile IC/BC approach is performed to demonstrate improvement of considering tropopause. It is observed that without using tropopause information in the downscaling process, unrealistic O-3 concentrations are created at the upper layers of IC/BC. This phenomenon has caused over-prediction of surface O-3 in CMAQ. In addition, the amount of over-prediction is greatly affected by temperature and latitudinal location of the study domain. With the implementation of the algorithm, we have successfully resolved the incompatibility issues in the vertical layer structure between global and regional chemistry models to yield better surface O-3 predictions than profile IC/BC for both summer and winter conditions. At the same time, it improved the vertical O-3 distribution of CMAQ outputs. It is strongly recommended that the tropopause information should be incorporated into any two-way coupled global and regional models, where the tropospheric regional model is used, to solve the vertical incompatibility that exists between global and regional models.