Influência dos jatos em médios e baixos níveis nos processos de nuvem: estudo numérico de uma linha de instabilidade amaz?nica

摘要

Squall lines (SL) are multicellular storms and it is well known that factors such as vertical wind shear can act to organize their convection. However there is few evidences of how medium and low level jets can alter the cloud processes, and as a consequence to affect the intensity, duration and propagation of such systems. This work attempts to clarify those jets role by discussing a simulated case of an Amazon SL based on an atmospheric wind profile over Belem - Brazil at 12:00 UTC of May 30, 2008. To accomplish the proposed goal a set of eight numeric experiments, with different wind profiles was performed using the BRAMS model. The results showed that the occurrence of a deep and intense jet may increase ventilation in clouds, resulting in more evaporation and drying, i.e. more mass entrainment. If the entrainment is higher, it can influence downdrafts, cold pools, convergence ahead of the system, and updrafts, so that more energy can be available to the system. Thus, under these conditions SL are more likely to propagate at higher speed with longer life time.