scholarly journals WRF nested large-eddy simulations of deep convection during SEAC4RS

2017 ◽  
Vol 122 (7) ◽  
pp. 3953-3974 ◽  
Author(s):  
Nicholas K. Heath ◽  
Henry E. Fuelberg ◽  
Simone Tanelli ◽  
F. Joseph Turk ◽  
R. Paul Lawson ◽  
...  
Keyword(s):  
Deep Convection ◽  
Large Eddy Simulations ◽  
Large Eddy

Large-eddy simulations of convection initiation over heterogeneous, low terrain

2022 ◽  
Keyword(s):  
Kinetic Energy ◽  
Free Convection ◽  
Deep Convection ◽  
Physical Space ◽  
Peak Height ◽  
Spectral Shape ◽  
Large Eddy Simulations ◽  
Power Spectral ◽  
Large Eddy ◽  
Convection Initiation

Abstract Large-eddy simulations are conducted to investigate and physically interpret the impacts of heterogeneous, low terrain on deep-convection initiation (CI). The simulations are based on a case of shallow-to-deep convective transition over the Amazon River basin, and use idealized terrains with varying levels of ruggedness. The terrain is designed by specifying its power-spectral shape in wavenumber space, inverting to physical space assuming random phases for all wave modes, and scaling the terrain to have a peak height of 200 m. For the case in question, these modest terrain fields expedite CI by up to 2-3 h, largely due to the impacts of the terrain on the size of, and subcloud support for, incipient cumuli. Terrain-induced circulations enhance subcloud kinetic energy on the mesoscale, which is realized as wider and longer-lived subcloud circulations. When the updraft branches of these circulations breach the level of free convection, they initiate wider and more persistent cumuli that subsequently undergo less entrainment-induced cloud dilution and detrainment-induced mass loss. As a result, the clouds become more vigorous and penetrate deeper into the troposphere. Larger-scale terrains are more effective than smaller-scale terrains in promoting CI because they induce larger enhancements in both the width and the persistence of subcloud updrafts.

scholarly journals A Direct Measure of Entrainment

2010 ◽  
Vol 67 (6) ◽  
pp. 1908-1927 ◽  
Author(s):  
David M. Romps
Keyword(s):  
Spatial Distribution ◽  
Direct Measurement ◽  
Deep Convection ◽  
Large Eddy Simulations ◽  
The Other ◽  
Vertical Profiles ◽  
Direct Measure ◽  
Total Water ◽  
Convective Flux ◽  
Large Eddy

Abstract A method is introduced for directly measuring convective entrainment and detrainment in a cloud-resolving simulation. This technique is used to quantify the errors in the entrainment and detrainment estimates obtained using the standard bulk-plume method. The bulk-plume method diagnoses these rates from the convective flux of some conserved tracer, such as total water in nonprecipitating convection. By not accounting for the variability of this tracer in clouds and in the environment, it is argued that the bulk-plume equations systematically underestimate entrainment. Using tracers with different vertical profiles, it is also shown that the bulk-plume estimates are tracer dependent and, in some cases, unphysical. The new direct-measurement technique diagnoses entrainment and detrainment at the gridcell level without any recourse to conserved tracers. Using this method in large-eddy simulations of shallow and deep convection, it is found that the bulk-plume method underestimates entrainment by roughly a factor of 2. The directly measured entrainment rates are then compared to cloud height and cloud buoyancy. Contrary to existing theories, fractional entrainment is not found to scale like the inverse of height, the cloud buoyancy, or the gradient of cloud buoyancy. On the other hand, fractional detrainment is found to scale linearly with cloud buoyancy. Finally, direct measurement is used to diagnose the spatial distribution of entrainment and detrainment during the evolution of an individual deep cumulonimbus.

Automotive Flow and Acoustic Predictions using Large Eddy Simulations

2012 ◽  
Vol 39 (3) ◽  
pp. 272-289 ◽  
Author(s):  
Bahram Khalighi ◽  
Gianluca Iaccarino ◽  
Yaser Khalighi
Keyword(s):  
Large Eddy Simulations ◽  
Large Eddy

Large-eddy simulations and lidar measurements of vortex-pair breakup in aircraft wakes

AIAA Journal ◽  
1998 ◽  
Vol 36 ◽  
pp. 1439-1445 ◽  
Author(s):  
D. C. Lewellen ◽  
W. S. Lewellen ◽  
L. R. Poole ◽  
C. A. Hostetler ◽  
R. J. DeCoursey ◽  
...  
Keyword(s):  
Vortex Pair ◽  
Large Eddy Simulations ◽  
Large Eddy ◽  
Lidar Measurements
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