This event has been canceled.

Speaker – Ademe Mekonnen, NC Agricultural & Technical University (NCAT)

Seminar Title – The Role of Different Types of Deep Convection on Easterly Waves Initiation over Africa

Abstract – Satellite-observed data from the International Satellite Cloud Climatology Project (ISCCP) suggests that African easterly waves (AEWs) form in association with a ‘‘transition’’ process from smaller and scattered convection into larger and organized mesoscale convective activity. Analysis based on long years of ISCCP and reanalysis datasets show that increasing intradiurnal activity, atmospheric instability, and specific humidity precede the development of well-organized convection over east African highlands. Atmospheric instability favors a high frequency of scattered, isolated convection to the east of the east African highlands, first, followed by a continuing and large increase in instability and increasing humidity, which supports well-organized larger-scale convection. The timing of the changes of thermodynamic variables shows that the dominant transition process is scattered, with weakly organized convection transitioning into the well-organized mesoscale convection, and this initiates the AEWs. Slightly before the mesoscale convection peaks over the Ethiopian highlands, low-level moist westerlies, low- to midlevel wind shear, and positive relative vorticity increase over the region. Evidence shows that the large scale and local environment enables the scattered and less well-organized convection to merge and form larger and well-organized convection. The dynamic processes suggest that the dominant pathway for AEW initiation is scattered convection transitioning to large and well-organized convection over the Ethiopian highlands and this initiates AEWs westward of the Ethiopian highlands.