Characterizing warm-ENSO variability in the Equatorial Pacific

An OLR Perspective

A.M. Chiodi

D.E. Harrison

(submitted to J. Climate)

Smith et al. (1999) J. Climate

Warm-event US impacts

Rationale for an OLR-ENSO Index

Conditions during lists of years of extreme ENSO-state provide a statistical basis for seasonal climate forecasting

Tropical atmospheric heating anomalies provide a dynamical basis for tropical and extra-tropical ENSO-related seasonal climate anomalies

OLR is offers a more direct link to anomalous atmospheric heating

Region of interest: Eastern Central Pacific

Region of interest: Eastern Central Pacific

Eastern Central Pacific OLRA Index

Event-like behavior

Gaussian-type behavior

Extra-Tropical Atmospheric Anomalies

ConclusionsA distinctive type of OLR behavior has been seen in the eastern central Pacific since OLR measurements have become reliably available.

Events of 1982-83, 1986-87, 1991-92 and 1997-98 stand out from background variability.

Substantial atmospheric circulation anomalies occur over the N. Pacific and N. America in years distinguished by OLR. The case for tropically-driven anomalies is less clear in years with ENSO-status based on some indices but that are not distinctive from an OLR perspective.

It makes sense to classify the OLR-distinguished events differently from others.

The OLR events were often distinguished in time to be of some use to DJF and later seasonal climate prediction efforts, though operational SSTA indices usually gave earlier indications.