OS025-0002
Atlantic Niño/Niña influences on Atlantic tropical storm activity and their modulation of the ENSO teleconnection
Thursday, 10 December 2020
Poster
Dongmin Kim, Cooperative Institute for Marine and Atmospheric Studies Miami, Miami, FL, United States, Sang-Ki Lee, University of Miami, Cooperative Institute for Marine and Atmospheric Studies, Miami, FL, United States, Hosmay Lopez, NOAA Miami, Miami, FL, United States, Gregory R Foltz, NOAA/AOML, Miami, FL, United States, Caihong Wen, NOAA/CPC college park, College Park, MD, United States and Ghassan Alaka, NOAA/AOML/Hurricane Research Division, Key Biscayne, FL, United States
Abstract:
Atlantic tropical storms (TS) and their associated severe storm surge and coastal flooding cause loss of human lives and damage to properties. It is well known that the seasonal activity of Atlantic TS is largely modulated by tropical Pacific and Atlantic sea surface temperature anomalies (SSTAs) associated with El Niño-Southern Oscillation (ENSO) and Atlantic meridional mode (AMM). However, ENSO is typically in a developing phase during the peak season of Atlantic hurricane (August–October), and AMM usually develops in boreal spring and often dissipates before August. In the tropical Atlantic, the leading mode of SST variability in boreal summer and fall is Atlantic Niño/Niña, characterized by warm/cold SSTAs in the eastern equatorial Atlantic that often persist through the Atlantic hurricane peak season. Nevertheless, the relationship between Atlantic Niño/Niña Atlantic TS activity has not yet been explored.
This is the first systematic study of the physical and statistical links between Atlantic Niño/Niña and Atlantic TS. Our analysis of observational and reanalysis datasets during 1948-2019, together with model experiments, shows that Atlantic Niño strengthens the Atlantic inter tropical convergence zone, increasing rainfall over the west African sub-Sahel region and African easterly waves. Additionally, the enhanced atmospheric convection produces low-level westerly wind anomalies over the tropical North Atlantic, which in turn increase low-level relative vorticity and decrease vertical wind shear over the Atlantic TS main development region (MDR). These atmospheric conditions over the MDR are favorable for increasing Atlantic TS activity. Further analysis shows that the tendency for El Niño to suppress Atlantic TS activity is amplified during Atlantic Niña and weakened during Atlantic Niño. Conversely, favorable conditions for Atlantic TS activity during La Niña events are amplified during Atlantic Niño, but suppressed during Atlantic Niña. This study suggests that Atlantic Niño/Niña may aid to improve the current seasonal prediction skill of Atlantic TS activity.
