Katharopoulos Ioannis, Brunner Dominik, Emmenegger Lukas, Leuenberger Markus, Henne Stephan
Laboratory for Air Pollution/Environmental Technology, Swiss Federal Laboratories for Materials Science and Technology (Empa), Dübendorf, Switzerland.
Institute for Atmospheric and Climate Science, ETH Zürich, Zurich, Switzerland.
Boundary Layer Meteorol. 2022;185(1):129-160. doi: 10.1007/s10546-022-00728-3. Epub 2022 Aug 5.
Lagrangian particle dispersion models (LPDMs) are frequently used for regional-scale inversions of greenhouse gas emissions. However, the turbulence parameterizations used in these models were developed for coarse resolution grids, hence, when moving to the kilometre-scale the validity of these descriptions should be questioned. Here, we analyze the influence of the turbulence parameterization employed in the LPDM FLEXPART-COSMO model. Comparisons of the turbulence kinetic energy between the turbulence schemes of FLEXPART-COSMO and the underlying Eulerian model COSMO suggest that the dispersion in FLEXPART-COSMO suffers from a double-counting of turbulent elements when run at a high resolution of . Such turbulent elements are represented in both COSMO, by the resolved grid-scale winds, and FLEXPART, by its stochastic parameterizations. Therefore, we developed a new parametrization for the variations of the winds and the Lagrangian time scales in FLEXPART in order to harmonize the amount of turbulence present in both models. In a case study for a power plant plume, the new scheme results in improved plume representation when compared with in situ flight observations and with a tracer transported in COSMO. Further in-depth validation of the LPDM against methane observations at a tall tower site in Switzerland shows that the model's ability to predict the observed tracer variability and concentration at different heights above ground is considerably enhanced using the updated turbulence description. The high-resolution simulations result in a more realistic and pronounced diurnal cycle of the tracer concentration peaks and overall improved correlation with observations when compared to previously used coarser resolution simulations (at 7 km 7 km). Our results indicate that the stochastic turbulence schemes of LPDMs, developed in the past for coarse resolution models, should be revisited to include a resolution dependency and resolve only the part of the turbulence spectrum that is a subgrid process at each different mesh size. Although our new scheme is specific to COSMO simulations at resolution, the methodology for deriving the scheme can easily be applied to different resolutions and other regional models.
The online version contains supplementary material available at 10.1007/s10546-022-00728-3.
拉格朗日粒子扩散模型（LPDMs）常用于温室气体排放的区域尺度反演。然而，这些模型中使用的湍流参数化是为粗分辨率网格开发的，因此，当应用于千米尺度时，这些描述的有效性值得质疑。在此，我们分析了LPDM FLEXPART - COSMO模型中使用的湍流参数化的影响。FLEXPART - COSMO的湍流方案与基础欧拉模型COSMO之间的湍流动能比较表明，当以高分辨率运行时，FLEXPART - COSMO中的扩散存在湍流元素的重复计算问题。此类湍流元素在COSMO中由解析网格尺度风表示，在FLEXPART中由其随机参数化表示。因此，我们为FLEXPART中的风变化和拉格朗日时间尺度开发了一种新的参数化方法，以协调两个模型中存在的湍流量。在一个电厂烟羽的案例研究中，与原位飞行观测以及在COSMO中传输的示踪剂相比，新方案能改善烟羽表示效果。进一步针对瑞士一个高塔站点的甲烷观测对LPDM进行深入验证表明，使用更新后的湍流描述，该模型预测不同地面高度处观测到的示踪剂变异性和浓度的能力得到显著增强。与之前使用的较粗分辨率模拟（7千米×7千米）相比，高分辨率模拟导致示踪剂浓度峰值出现更现实、更明显的日循环，并且与观测的总体相关性得到改善。我们的结果表明，过去为粗分辨率模型开发的LPDM随机湍流方案应重新审视，以纳入分辨率依赖性，并仅解析在每个不同网格大小下作为亚网格过程的湍流谱部分。尽管我们的新方案特定于分辨率下的COSMO模拟，但推导该方案的方法可轻松应用于不同分辨率和其他区域模型。
在线版本包含可在10.
