Large-Eddy Simulation of Dry and Moist Atmospheric Boundary Layers and Analysis of the Model Convergence
By using the large eddy simulation （LES） version of the Weather Research and Forecasting （WRF） model， vertical structure and the feature of turbulent transportation of shallow-convective-cloud-topped atmospheric convective boundary layer was simulated in addition to the idealized dry convective boun...
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| Main Authors: | , |
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| Format: | Article |
| Language: | zho |
| Published: |
Science Press, PR China
2024-12-01
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| Series: | Gaoyuan qixiang |
| Subjects: | |
| Online Access: | http://www.gyqx.ac.cn/EN/10.7522/j.issn.1000-0534.2024.00039 |
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| Summary: | By using the large eddy simulation （LES） version of the Weather Research and Forecasting （WRF） model， vertical structure and the feature of turbulent transportation of shallow-convective-cloud-topped atmospheric convective boundary layer was simulated in addition to the idealized dry convective boundary layer on oceanic surface.Numerical convergence of LES model was analyzed with the model results in different resolutions.The results showed that the dry convective boundary layer was vigorous.Approximately 1.15 km of the planetary boundary layer height was simulated with the LES in different resolutions.Vertical uniform structure of the averaged potential temperature （θ）， mixing ratio of water vapor （qv） and horizontal wind （u and v） were shown in the idealized dry convective boundary layer but with large vertical gradients in the near surface layer and the top of the boundary layer.Higher resolution model resolved more detailed structure of convective bubbles within the dry convective boundary layer， larger variance of potential temperature in the entrainment layer， vertical uniform distribution of the averaged quantities within the simulated mixed layer extending more closing to the surface， and the errors in LES model under coarse resolution were mainly concentrated in the lower boundary layer and near the inversion layer.The higher resolution LES model showed larger resolved sensible heat flux while the total flux remained.In the case of shallow-convective-cloud-topped boundary layer， obvious different boundary layer structure was displayed in comparison with that of the dry convective boundary layer.Conditionally unstable layer existed over the mixing layer， and mixing layer height dropped.Vertical profiles of averaged θ， qv， u and v showed similar structure in the mixing layer as that in the convective boundary layer.The averaged meteorological quantities in the lower mixing layer were uniformly distributed in vertical direction.In the cloudy layer， however， positive heat flux and vertical turbulent kinetic energy appeared.Negative heat flux was observed from the top of mixing layer to the lower cloudy layer， which reflected the weak inverse temperature and entrainment at top of mixing layer.Lower-resolution model simulated more deviations of the top of temperature inversion， and mean wind velocity and fluxes near surface.The large eddy simulation model tended to converge at 40 m resolution in the vigorously developing dry convective boundary layer case while it converged at 30 m resolution in the shallow-convective-cloud-topped boundary layer.The atmospheric boundary layer with lower mixing layer height needs to be simulated using a higher resolution LES model. |
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| ISSN: | 1000-0534 |