Horizontal convective rolls

Although horizontal convective rolls, also known as cloud streets, have been clearly seen in satellite photographs for the last 30 years, their development is poorly understood, due to a lack of observational data.

Research has shown these eddies to be significant to the vertical transport of momentum, heat, moisture, and air pollutants within the boundary layer.

However the frequent presence of the horizontal roll vortices in the PBL, which represent an organization of the turbulence (coherent structures), indicate that the diffusivity approximation is not adequate.

Ekman's solution has an intrinsic inflectional wind profile that was found to be unstable to long waves corresponding to the organized large vortices scale.

[3] The nonlinear theory showed that the growth of these finite perturbation waves modifies the mean flow, eliminating the dynamic inflectional instability energy so that equilibrium is obtained.

[7][1] This solution for the layer containing the PBL-scale roll wavelength requires a modification of the flux transports to accommodate modeling of the advective motion of the large vortices.

The nonlinear solution, with explicit description of the finite perturbation coherent structure rolls constitutes a significant contribution to the theory of chaos for organization of turbulence.