Characteristics
Horizontal convective rolls are counter-rotating vortex rolls that are nearly aligned with the mean wind of the convective boundary layer. Early theory on the features predict that the vortices may be aligned up to 30° to the left for stable environments, 18° to the left for neutral environments, and nearly parallel to the mean wind for unstable environments. This theory has been supported by aircraft observations from several field experiments.
The depth of a vortex is usually the depth of the boundary layer, which is generally on the order of 1–2 km. A vortex pair usually has a lateral to vertical dimension ratio of 3:1. Experimental studies have shown that the aspect ratio (a ratio of roll wavelength to boundary layer depth) has been found to vary between 2.2:1 and 6.5:1, with an average aspect ratio of 5.7:1. However, in some situations, the aspect ratio may be as large as 10:1. Large aspect ratios for rolls are believed to be caused by non-linear interactions at small convective scales, which are not predicted by theoretical calculations. The lifetime of a convective roll can last from 1 to 72 hours.
If the environmental air is near saturation, condensation may occur in updrafts produced from the vortex rotation. The sinking motion produced between alternating pairs of rolls, combined with the updrafts, will produce cloud streets. ] often use the updrafts produced by cloud streets enabling them to fly straight for long distances while still climbing.
Read more about this topic: Horizontal Convective Rolls