Climate Program Office News

Different Control of Tropical Cyclone Activity in the Eastern Pacific for Two Types of El Niño

  • 1 March 2016
  • Number of views: 1691

As the current El Niño event winds down, we can reflect on its influence over tropical cyclone activity in 2015.

El Niño somewhat suppressed Atlantic tropical cyclone activity (though perhaps not as much as was expected) and enhancing Pacific tropical cyclone activity to make 2015 the second most active Pacific hurricane season on record. This was likely due, in part, to the "flavor" of El Niño that we experienced--a canonical, Eastern Pacific El Niño rather than a Modoki, Central Pacific El Niño.

Newly published research in Geophysical Research Letters by Boucharel et al.--and supported by CPO's Climate Variability and Predictability program--seeks to understand these modes of expression, or "flavors," of El Niño, and their influence on tropical cyclones.

From the abstract:

We find that the oceanic control, through meridional redistribution of subsurface heat, is the main driver of tropical cyclone activity during the hurricane season following Eastern Pacific events. In contrast, atmospheric conditions tend to be destructive to tropical cyclone intensification after those events. The altered atmospheric circulation, in particular the reduction of vertical wind shear and the increase in relative humidity, tends to be more influential in controlling tropical cyclone activity post Central Pacific events. However, unlike for subsurface heat, these changes in atmospheric conditions are not statistically distinct between these two ENSO flavors—although they are consistent across all atmospheric data sets tested. Overall, unlike after Eastern Pacific El Niño events, the hurricane season activity following a Central Pacific event is not significantly different from neutral or even La Niña years.

Access the paper, at: dx.doi.org/10.1002/2016GL067728

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