{"title":"On the Sensitivity of Large Eddy Simulations of the Atmospheric Boundary Layer Coupled with Realistic Large Scale Dynamics","authors":"P. Giani, Paola Crippa","doi":"10.1175/mwr-d-23-0101.1","DOIUrl":null,"url":null,"abstract":"\nWe present a new ensemble of 36 numerical experiments aimed at comprehensively gauging the sensitivity of nested Large Eddy Simulations (LES) driven by large scale dynamics. Specifically, we explore 36 multiscale configurations of the Weather Research and Forecasting (WRF) model to simulate the boundary layer flow over the complex topography at the Perdigão field site, with five nested domains discretized at horizontal resolutions ranging from 11.25 kilometers to 30 meters. Each ensemble member has a unique combination of the following input factors, (i) large-scale initial and boundary conditions, (ii) subgrid turbulence modeling in the gray zone of turbulence, (iii) subgrid-scale (SGS) models in LES simulations and (iv) topography and land cover datasets. We probe their relative importance for LES calculations of velocity, temperature and moisture fields. Variance decomposition analysis unravels large sensitivities to topography and land use datasets and very weak sensitivity to the LES SGS model. Discrepancies within ensemble members can be as large as 2.5 m s−1 for the time-averaged near-surface wind speed on the ridge, and as large as 10 m s−1 without time averaging. At specific time points, a large fraction of this sensitivity can be explained by the different turbulence models in the gray zone domains. We implement a horizontal momentum and moisture budget routine in WRF to further elucidate the mechanisms behind the observed sensitivity, paving the way for an increased understanding of the tangible effects of the gray zone of turbulence problem.","PeriodicalId":18824,"journal":{"name":"Monthly Weather Review","volume":null,"pages":null},"PeriodicalIF":2.8000,"publicationDate":"2024-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Monthly Weather Review","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.1175/mwr-d-23-0101.1","RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"METEOROLOGY & ATMOSPHERIC SCIENCES","Score":null,"Total":0}
引用次数: 0
Abstract
We present a new ensemble of 36 numerical experiments aimed at comprehensively gauging the sensitivity of nested Large Eddy Simulations (LES) driven by large scale dynamics. Specifically, we explore 36 multiscale configurations of the Weather Research and Forecasting (WRF) model to simulate the boundary layer flow over the complex topography at the Perdigão field site, with five nested domains discretized at horizontal resolutions ranging from 11.25 kilometers to 30 meters. Each ensemble member has a unique combination of the following input factors, (i) large-scale initial and boundary conditions, (ii) subgrid turbulence modeling in the gray zone of turbulence, (iii) subgrid-scale (SGS) models in LES simulations and (iv) topography and land cover datasets. We probe their relative importance for LES calculations of velocity, temperature and moisture fields. Variance decomposition analysis unravels large sensitivities to topography and land use datasets and very weak sensitivity to the LES SGS model. Discrepancies within ensemble members can be as large as 2.5 m s−1 for the time-averaged near-surface wind speed on the ridge, and as large as 10 m s−1 without time averaging. At specific time points, a large fraction of this sensitivity can be explained by the different turbulence models in the gray zone domains. We implement a horizontal momentum and moisture budget routine in WRF to further elucidate the mechanisms behind the observed sensitivity, paving the way for an increased understanding of the tangible effects of the gray zone of turbulence problem.
期刊介绍:
Monthly Weather Review (MWR) (ISSN: 0027-0644; eISSN: 1520-0493) publishes research relevant to the analysis and prediction of observed atmospheric circulations and physics, including technique development, data assimilation, model validation, and relevant case studies. This research includes numerical and data assimilation techniques that apply to the atmosphere and/or ocean environments. MWR also addresses phenomena having seasonal and subseasonal time scales.