Publication Date:
2011-02-08
Description:
Equatorial westerly wind bursts (WWBs) and their relationship with El Niño–Southern Oscillation (ENSO) in the 18 climate models presented in the World Climate Research Programme's Coupled Model Intercomparison Project phase 3 (CMIP3) are examined. Some models depict a realistic eastward shift of collective occurrences of WWBs over the Pacific as the warm pool expands eastward. These models that depict the frequent western Pacific WWBs preceding El Niño peak, known to trigger or enhance El Niño, tend to reproduce westerly background states and ENSO more accurately. Thus the reproducibility of the westerly background states is suggested to be fundamental for WWB occurrences as well as the following El Niño. Although WWBs generate with active convection in most of the models as observations, various kinds of intraseasonal disturbances that cause the active convection are found. It is suggested that organized convection is essential for the WWB generation but is prepared by each model's own dominant mode in the tropics. Under global warming, WWBs tend to increase over the eastern Pacific and decrease over the Indian Ocean whereas the total number of WWBs does not change consistently. This might arise from an increase of short-period convective disturbances over the eastern Pacific due to a sea surface temperature increase. Although there is a weak relationship between changes in the ENSO amplitude and the eastern Pacific WWBs in general, good models reproducing the WWB-ENSO relationship in the current climate tend to show consistent changes, suggesting the possibility of the eastern Pacific WWBs to intensify ENSO.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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