The role of land-atmosphere and aerosol interactions on meso-scale convective weather systems across West Africa

Abstract

This dissertation investigates the modulating effects of land-atmosphere and aerosol interactions on meso-scale convective systems across the sub-Saharan West Africa region, and aims at providing a value-added contribution towards better understanding of the controlling mechanisms for these interactions, in order to improve predictability of the highly frequent, high-impact meso-scale convective systems. It is very well known that aerosols alter the surface energy budget resulting into complex and multi-scale interactions between the land-atmosphere and mesoscale convective systems, which are yet to be fully understood. In this study, we used a highly proven successful cognitive recognition artificial neural network intelligence problem solving tool - Self-Organizing Maps (SOM) in investigating the modulating effects of aerosol-land-atmosphere interactions for enhancing the predictability of meso-scale convective systems. The SOM method is not yet commonly used by climate scientists for solving climate research problems. For the first time in this research - at least to the best of our knowledge - we used the SOM method to solve climate research problems over Africa. Our results show very strong seasonal influence in determining the dominant controlling variable (e.g. soil moisture, aerosols) on the interactions between atmospheric aerosols, meso-scale convective systems and land-surface properties across the study region. It was also found that these controlling variables are generally very significant in modulating atmospheric interactions across the region during the monsoon (wet) seasons than during the nonmonsoon (dry) seasons. Furthermore, results showed that even though there is noticeable control by aerosols on the interactions between land-atmosphere and meso-scale convective systems, available surface soil moisture exerts the most dominant control across the region especially during the active convective period (monsoon season) of the year. Results further showed that soil moisture has the potential to control the convective available potential energy (CAPE) up to about 79% during the monsoon season and up to about 67% during the non-monsoon seasons, while aerosols can control CAPE up to about 67% during monsoon and up to about 23% during the non-monsoon season.