What are horizontal convective rolls?

Horizontal Convective Rolls

Horizontal convective rolls, also known as horizontal roll vortices or cloud streets, are long rolls of counter-rotating air that are oriented approximately parallel to the ground in the planetary boundary layer. 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. From the ground they appear as rows of cumulus or cumulus-type clouds aligned parallel to the low-level wind. Research has shown these eddies to be significant to the vertical transport of momentum, heat, moisture, and air pollutants within the boundary layer. Cloud streets are usually more or less straight, but rarely cloud streets assume paisley patterns when the wind driving the clouds encounters an obstacle. Those cloud formations are known as von Kármán vortex streets.

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Some articles on horizontal convective rolls:

Horizontal Convective Rolls - Development and Required Environmental Conditions
... The exact process that leads to the formation of horizontal convective rolls is not well understood, but most formation theories involve a combination of thermal or ... In thermal instabilities, turbulent energy that forms the rolls is produced from buoyancy ... too unstable, and will lead to cellular, instead of roll convection ...

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