On the Nature of the Transition Between Roll and Cellular Organization in the Convective Boundary Layer

Scott Salesky; Marcelo Chamecki; Elie Bou-Zeid

doi:10.1007/s10546-016-0220-3

Salesky, Scott; Chamecki, Marcelo; Bou-Zeid, Elie

2016-11-29 00:00:00

Both observational and numerical studies of the convective boundary layer (CBL) have demonstrated that when surface heat fluxes are small and mean wind shear is strong, convective updrafts tend to organize into horizontal rolls aligned within 10–20 $$^\circ $$ ∘ of the geostrophic wind direction. However, under large surface heat fluxes and weak to negligible shear, convection tends to organize into open cells, similar to turbulent Rayleigh-Bénard convection. Using a suite of 14 large-eddy simulations (LES) spanning a range of $$-z_i/L$$ - z i / L between zero (neutral) and 1041 (highly convective), where $$z_i$$ z i is the CBL depth and L is the Obukhov length, the transition between roll- and cellular-type convection is investigated systematically for the first time using LES. Mean vertical profiles including velocity variances and turbulent transport efficiencies, as well the “roll factor,” which characterizes the rotational symmetry of the vertical velocity field, indicate the transition occurs gradually over a range of $$-z_i/L$$ - z i / L ; however, the most significant changes in vertical profiles and CBL organization occur from near-neutral conditions up to about $$-z_i/L \approx $$ - z i / L ≈ 15–20. Turbulent transport efficiencies and quadrant analysis are used to characterize the turbulent transport of momentum and heat with increasing $$-z_i/L$$ - z i / L . It is found that turbulence transports heat efficiently from weakly to highly convective conditions; however, turbulent momentum transport becomes increasingly inefficient as $$-z_i/L$$ - z i / L increases.

http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png

Boundary-Layer Meteorology Springer Journals

http://www.deepdyve.com/lp/springer-journals/on-the-nature-of-the-transition-between-roll-and-cellular-organization-emy0oeTuu9

On the Nature of the Transition Between Roll and Cellular Organization in the Convective Boundary Layer

$Both observational and numerical studies of the convective boundary layer (CBL) have demonstrated that when surface heat fluxes are small and mean wind shear is strong, convective updrafts tend to organize into horizontal rolls aligned within 10–20 $$^\circ $$ ∘ of the geostrophic wind direction. However, under large surface heat fluxes and weak to negligible shear, convection tends to organize into open cells, similar to turbulent Rayleigh-Bénard convection. Using a suite of 14 large-eddy simulations (LES) spanning a range of $$-z_i/L$$ - z i / L between zero (neutral) and 1041 (highly convective), where $$z_i$$ z i is the CBL depth and L is the Obukhov length, the transition between roll- and cellular-type convection is investigated systematically for the first time using LES. Mean vertical profiles including velocity variances and turbulent transport efficiencies, as well the “roll factor,” which characterizes the rotational symmetry of the vertical velocity field, indicate the transition occurs gradually over a range of $$-z_i/L$$ - z i / L ; however, the most significant changes in vertical profiles and CBL organization occur from near-neutral conditions up to about $$-z_i/L \approx $$ - z i / L ≈ 15–20. Turbulent transport efficiencies and quadrant analysis are used to characterize the turbulent transport of momentum and heat with increasing $$-z_i/L$$ - z i / L . It is found that turbulence transports heat efficiently from weakly to highly convective conditions; however, turbulent momentum transport becomes increasingly inefficient as $$-z_i/L$$ - z i / L increases.$

References (103)

Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 7-Day Trial for You or Your Team.

Learn More →

On the Nature of the Transition Between Roll and Cellular Organization in the Convective Boundary Layer

On the Nature of the Transition Between Roll and Cellular Organization in the Convective Boundary Layer

Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 7-Day Trial for You or Your Team.

Learn More →

On the Nature of the Transition Between Roll and Cellular Organization in the Convective Boundary Layer

On the Nature of the Transition Between Roll and Cellular Organization in the Convective Boundary Layer

References (103)

Abstract

Journal

Recommended Articles

There are no references for this article.

Our policy towards the use of cookies