Multidecadal Modulations of ENSO influence on Tropical Atlantic cyclogenesis

The impact of ENSO (El Niño Southern Oscillation) events on the development of tropical cyclones in the Eastern Tropical North Atlantic is highlighted, focusing on decadal variations of the interannual relationship at the Senegalese coast, which is the main cyclone development region (MDR). The enhancement of North Atlantic tropical cyclones by the Atlantic Niño and the Pacific El Niño Southern Oscillation (ENSO) is diagnosed. An approach based on  composites of anomalous positive or negative years in terms of cyclone activity is used. Based on 20yr-correlations between the number of cyclones that are born in the MDR and ENSO index, we have selected two different periods of study (period1 (P1): 1954-1973; and period2 (P2): 1986-2005). Results show an increase in the SST impact in cyclone generation from P1 to P2 and intensification of cyclones number over the Senegalese coasts. Likewise, the spatial distribution of the dynamic and thermodynamic parameters used in this composite study shows strong variations between the two periods. Our findings suggest that decadal changes in climatological conditions have a significant effect on the MDR. Additionally, the changes in the interannual signal appear to be related to the concomitant action of interannual SST anomalies over the whole tropical basins.