Multidecadal Modulations of ENSO Influence on Tropical Atlantic Cyclogenesis Keywords: TROPICAL CYCLONES; ENSO; MULTIDICADAL; MDR; EQUATORIAL ATLANTIC; AEWs

Multidecadal Modulations of ENSO influence on Tropical Atlantic cyclogenesis

Adama Badiane¹, Belén Rodríguez-Fonseca^2,3, Teresa Losada², Juan Jesús González-Alemán⁴, Abdou Lahat Dieng¹, and Saidou Moustapha Sall¹

¹ Laboratoire de Physique de l’Atmosphère et de l’Océan -Siméon Fongang, Ecole Supérieure Polytechnique de l’Université Cheikh Anta Diop (UCAD), Dakar,

² Universidad Complutense de Madrid, Departamento de Física de la Tierra y Astrofísica, Facultad de Físicas, 28040 Madrid, Spain

³ Instituto de Geociencias IGEO, UCM-CSIC, Madrid, Spain

⁴ AEMET, Madrid, Spain.

Decadal variations of the interannual relationship between ENSO and cyclogenesis at the Senegalese coast, which is the main cyclone development region (MDR) are described. Based on 20yr-correlations between the number of cyclones that are born in the MDR and ENSO and Atl3 indices, we have found different behaviors for different periods of study (period 1: 1954-1973, period 2: 1986-2005 and period 3: 1993-2012. The results show that period 2 presents the highest scores of negative correlations between ENSO and tropical Atlantic cyclogenesis and that tropical Atlantic cyclogenesis is more related to Central Pacific (CP) anomalies during period 1 and to Eastern Pacific (EP) during period 2. The results for period3 show that in the last decades CP Niños impact more in the center of the Atlantic Ocean basin, while near the Senegalese coast the relationship between tropical Atlantic cyclones and tropical SST is stronger with EP Niños that appear anticorrelated to SST anomalies in the Equatorial Atlantic. Additionally, the changes in the interannual signal appear to be related to the concomitant action of interannual SST anomalies over the whole tropical basins.

Finally, the results for period 3 show that in the last decades CP Niños impact more in the center of the Atlantic Ocean basin, while near the Senegalese coast, the relationship between tropical Atlantic cyclones and tropical SST is stronger with EP Niños that appear anticorrelated to SST anomalies in the Equatorial Atlantic. For the latter, enhanced moisture flux from the Equatorial Atlantic to West Africa seems to be feeding AEW that led the development of tropical cyclones.

Keywords: Tropical cyclones; ENSO; Multidecadal; MDR; Equatorial Atlantic; AEWs