Influences of strong and moderate ENSO events on the Maranh?o precipitation from the western equatorial Atlantic SST anomalies

This study analyzed the influence of strong and moderate El Niho-Southern Oscillation (ENSO) events on the seasonal and interannual variabilities of the sea surface temperature (SST) in the Western Equatorial Atlantic (WEA) Ocean and how the precipitation over the state of Maranhao, in Brazil, responds to the zonal teleconnection. To evaluate the ENSO magnitude and phase in the four Niho regions (1+2, 3, 3.4, and 4), the SODA 3.3.1 oceanic reanalysis database for the period from 1980 to 2015 was used. Our results showed that the La Niha phase with moderate magnitude was the most predominant among the 70 events analyzed, with Niho 3.4 presenting the highest number (20) of ENSO events (both positive and negative phases). At lag = 0, we found that significant negative correlations prevailed between the WEA SST anomalies and ENSO index, with the region of Niho 3.4 showing the most significant correlations (r = -0.25). The whole events of El Niho and La Niha were, respectively, accompanied by a cooling and a heating of up to -0.6 degrees C or +0.8 degrees C in the WEA Ocean. The WEA SST anomalies during El Niho and La Niha events have, respectively, reduced and increased the precipitation in Maranhao around +/- 100 mm in a quarter. Strong El Niho events influence a greater precipitation deficit in Maranhao than moderate El Niho events. Moderate La Niha events have more pronounced influence on the precipitation over Maranhao than strong La Niha events do, especially on the negative anomalies. Our results showed that the central, northern, and eastern tip sectors of the state are the most affected by this zonal teleconnection. We concluded that ENSO's significant influences on the WEA SST seasonal variability, added to the performance of the Atlantic Meridional Mode (Soares 2019), determine the quality of the rainy season (March-April-May) in the state of Maranhao.