|
Stacks Logo
Advanced Search
Select up to three search categories and corresponding keywords using the fields to the right. Refer to the Help section for more detailed instructions.
 
 
Help
Clear All Simple Search
Advanced Search
The Nature of the Stochastic Wind Forcing of ENSO
  • Published Date:
    2018
  • Source:
    Journal of Climate, 31(19), 8081-8099.
Filetype[PDF-4.52 MB]


Details:
  • Description:
    El Nino-Southern Oscillation (ENSO) is commonly viewed as a low-frequency tropical mode of coupled atmosphere-ocean variability energized by stochastic wind forcing. Despite many studies, however, the nature of this broadband stochastic forcing and the relative roles of its high- and low-frequency components in ENSO development remain unclear. In one view, the high-frequency forcing associated with the subseasonal Madden-Julian oscillation (MJO) and westerly wind events (WWEs) excites oceanic Kelvin waves leading to ENSO. An alternative view emphasizes the role of the low-frequency stochastic wind components in directly forcing the low-frequency ENSO modes. These apparently distinct roles of the wind forcing are clarified here using a recently released high-resolution wind dataset for 1990-2015. A spectral analysis shows that although the high-frequency winds do excite high-frequency Kelvin waves, they are much weaker than their interannual counterparts and are a minor contributor to ENSO development. The analysis also suggests that WWEs should be viewed more as short-correlation events with a flat spectrum at low frequencies that can efficiently excite ENSO modes than as strictly high-frequency events that would be highly inefficient in this regard. Interestingly, the low-frequency power of the rapid wind forcing is found to be higher during El Nino than La Nina events, suggesting a role also for state-dependent (i.e., multiplicative) noise forcing in ENSO dynamics.

  • Document Type:
  • Main Document Checksum:
  • Supporting Files:
    No Additional Files
You May Also Like: