Séminaire
The West African Monsoon is a significant component of the global monsoon system, delivering the majority of annual precipitation for the Sahel and varying on timescales ranging from seasons to decades and beyond. Much of the internal variability of this system is driven by sea surface temperature anomalies and their resulting atmospheric teleconnections linking oceanic changes to land-based precipitation, the complexity of which is far from understood. In this talk, I will show results from a moisture budget decomposition for the Sahel, which helps us to understand the processes which govern regional hydroclimate variability on the interannual time scale. The results show how warm conditions in the Eastern Tropical Pacific remotely force anomalously dry conditions primarily through affecting the low troposphere mass divergence field. This study is used as a baseline to then compare situations where ENSO forcing is combined with other strong drivers of variability (e.g. North Atlantic variability) known to influence the region. The superposition of these anomalies is important and we try to disentangle them using some of the same diagnostic techniques. Results from this work have particular relevance for informing seasonal forecasting applications as such forecasts rely on the current state of the global ocean. An example of how the increased knowledge of oceanic effects on Sahel rainfall may be used will be discussed by detailing current efforts by the Agence Nationale de l'Aviation Civile et de la Météorologie (ANACIM) du Sénégal to deliver climate information and build resilience to climate variability locally.