Multi-nested WRF simulations for studying planetary boundary layer processes on the turbulence-permitting scale in a realistic mesoscale environment
Multi-nested WRF simulations for studying planetary boundary layer processes on the turbulence-permitting scale in a realistic mesoscale environment
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DOI：
10.1080/16000870.2020.1761740
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发表时间：
2020-01
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影响因子：
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通讯作者：
H. Bauer;S. K. Muppa;V. Wulfmeyer;A. Behrendt;K. Warrach‐Sagi;F. Späth
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文献类型：
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作者：
H. Bauer;S. K. Muppa;V. Wulfmeyer;A. Behrendt;K. Warrach‐Sagi;F. Späth
摘要天气研究和预报（WRF）模式应用于嵌套配置，从2.7公里的对流允许域通过灰区分辨率为900米和300米下降到100米的对流允许的规模。基于敏感性研究，这种方法进行了优化，以研究2013年4月24日在德国西部的HOPE实验期间晴空情况下PBL中小尺度过程的演变。结果进行了比较，从文献和高分辨率激光雷达观测活动期间收集的理论和实验结果。参数化湍流模拟能够捕捉边界层高度的时间演变，但几乎没有内部结构的边界层模拟。只有允许连续性的模拟才能再现早晨从稳定的夜间到白天的对流边界层的过渡，以及随后分解成湍流涡旋的过程。与激光雷达数据的比较表明，连续性允许的模拟再现了观测到的湍流统计数据。然而，在边界层的位温比观察到的低1 K，由湍流涡旋混合向上的表面温度较低造成的。模拟的边界层高度被低估了200米，反映在一个良好的捕获的特定湿度高达900米的高度和过度强烈的湿度下降以上的配置文件。该模型较好地描述了位温和比湿的变化特征。然而，整个边界层的模拟变率较低，不同高度的方差峰表明，该模型可能无法完全捕捉到边界层顶部的湍流过程。确定嵌套模拟和观测之间的系统差异表明，这种模式的方法过程研究和参数化测试的价值。
Abstract The Weather Research and Forecasting (WRF) model was applied in a nested configuration from a 2.7 km convection-permitting domain via grey-zone resolutions of 900 m and 300 m down to the 100 m turbulence-permitting scale. Based on sensitivity studies, this approach was optimized to investigate the evolution of small-scale processes in the PBL for a clear sky case during the HOPE experiment in western Germany on 24 April 2013. The results were compared with theoretical and experimental findings from literature and high-resolution lidar observations collected during the campaign. Simulations with parameterized turbulence were able to capture the temporal evolution of the PBL height, but almost no internal structure was simulated in the boundary layer. Only the turbulence-permitting simulations were capable of reproducing the morning transition from the stable nighttime to the daytime convective boundary layer and the following break-up into turbulent eddies. Comparisons with lidar data showed that the turbulence-permitting simulations reproduced the observed turbulence statistics. Nevertheless, the potential temperature in the boundary layer was 1 K cooler than observed, caused by a lower surface temperature mixed upward by the turbulent eddies. The simulated PBL height was underestimated by 200 m, reflected in a well-captured profile of specific humidity up to a height of 900 m and an overly strong decrease of moisture above. The general shape of the variance profiles of potential temperature and specific humidity were captured by the model. However, the simulated variability throughout the boundary layer was lower and the different heights of the variance peaks indicated that the model may not fully capture the turbulent processes at the top of the boundary layer. Identifying those systematic differences between nested simulations and observations demonstrated the value of this model approach for process studies and parameterization tests.