Picture: Cumulus convection. Credit: Taryn Kaahanui (Unsplash).
Convection that produces cumulus clouds is typically thought of as being made up of long continuous plumes of warm rising air, rather than shorter, incoherent plumes of around only 1km in vertical extent.
Global climate models tend to parameterise cumulus convection in the first form, but detailed numerical simulations and aircraft observations tend to support the latter for typical warm-season convection.
CLEX researchers used data from a wind profiler radar pair at Darwin, Australia, to determine the characteristics of individual up- and downdrafts observed at the site.
Most drafts were found to be less than 2 km in vertical extent. They also identified that the updraft length increased with rain rates. With extreme rain rates, the average updraft lengths were around 5km. These results are broadly consistent with other numerical modelling studies, but are in contrast to the common view that deep convection is dominated by continuous, deep drafts.
- Paper: Yeung, Nicholas K. H., Steven C. Sherwood, Alain Protat, Todd P. Lane, and Christopher Williams. ” A Doppler radar study of convective draft lengths over Darwin, Australia”, Monthly Weather Review (published online ahead of print 2021). https://doi.org/10.1175/MWR-D-20-0390.1