May 28, 2018 | Published by | ,

The processes governing the formation, maintenance, and propagation of tropical thunderstorms are not fully understood.

In the midlatitudes, established theory explains the maintenance of thunderstorms via an interaction between the wind shear (the change in wind speed with height) and cold air outflows (‘cold pools’) formed by the evaporation of rain. This theory, however, is less applicable to the tropics where the cold pools and wind shear are typically weaker.

Nonetheless, it has been hypothesised by many studies that cold pools  are critical to the initiation and maintenance of thunderstorms in the tropics.

In this study, we examine cold pools’ maintenance of thunderstorms in a suite of idealised numerical model experiments. In these experiments, the cold pools are artificially eliminated by suppressing evaporation after the thunderstorms become organised.

In contrast to expectations, the thunderstorms without cold pools actually intensify, demonstrating unequivocally that cold pools can be detrimental to convection.

Further investigations suggest that organised systems become maintained through atmospheric wave-convection interactions, which is a significantly different process to the established theory.

These results confirm the importance of wave-convection interactions as a key contributor to convective organisation in the tropics, a process absent from all parameterisations.