i
The Nature of the Stochastic Wind Forcing of ENSO
-
2018
-
Source: Journal of Climate, 31(19), 8081-8099.
[PDF-4.52 MB]
Details:
-
Journal Title:Journal of Climate
-
Personal Author:
-
NOAA Program & Office:
-
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.
-
Source:Journal of Climate, 31(19), 8081-8099.
-
DOI:
-
Document Type:
-
Rights Information:Other
-
Compliance:Submitted
-
Main Document Checksum:
-
Download URL:
-
File Type:
Related Documents
-
Mioduszewski, John;
Vavrus, Stephen...[PDF - 5.53 MB]
