Title: Degree of Simulated Suppression of Atlantic Tropical Cyclones Controlled by Flavour of El Niño

Journal: Nature Geoscience, 9, 155-160

Authors: Patricola, C.M.*, P. Chang and R. Saravanan

Abstract:El Niño/Southern Oscillation, the dominant mode of interannual climate variability, strongly influences tropical cyclone activity. During canonical El Niño, the warm phase, Atlantic tropical cyclones are suppressed. However, the past decades have witnessed different El Niño characteristics, ranging from warming over the east Pacific cold tongue in canonical events to warming near the warm pool, known as warm pool El Niño or central Pacific El Niño. Global climate models project possible future increases in intensity of warm pool El Niño. Here we use a climate model at a resolution sufficient to explicitly simulate tropical cyclones to investigate how these flavours of El Niño may affect such cyclones. We show that Atlantic tropical cyclones are suppressed regardless of El Niño type. For the warmest 10% of each El Niño flavour, warm pool El Niño is substantially less effective at suppressing Atlantic tropical cyclones than cold tongue El Niño. However, for the same absolute warming intensity, the opposite is true. This is because less warming is required near the warm pool to satisfy the sea surface temperature threshold for deep convection, which leads to tropical cyclone suppression through vertical wind shear enhancements. We conclude that an understanding of future changes in not only location, but also intensity and frequency, of El Niño is important for forecasts and projections of Atlantic tropical cyclone activity.