Precursors of ENSO Events from 27 Years of Satellite Data

Antonietta Capotondi, NOAA /ESRL, Physical Sciences Division, Boulder, CO, United States; University of Colorado, CIRES, Boulder, CO, United States and Lucrezia Ricciardulli, Remote Sensing Systems, Santa Rosa, CA, United States
The present study examines precursors for ENSO diversity using high-quality satellite observations of several key variables for the past 27 years, complemented by subsurface information from ocean reanalysis data. The observations consist of an extensive suite of ocean satellite retrievals from microwave sensors, radiometers and scatterometers, all inter-calibrated and consistently processed at Remote Sensing Systems. The data set covers the period 1988 to present, and is available at high temporal (twice daily) and spatial (0.25 degrees) resolutions.

Our objective is to clarify the relative role of large-scale atmospheric forcing from the Northern and Southern Hemispheres, as well as tropical atmospheric noise and ocean background conditions in triggering different ENSO types, thus providing insights in the event predictability and possible lead times. We first examine whether large-scale extra-tropical wind precursors exist for the El Niño/La Niña events during the satellite era, and how they relate with the many proposed in the literature. We then consider Westerly Wind Bursts (WWBs) activity for different types of ENSO events, and its possible interplay with extra-tropical influences. Special attention is devoted to the evolution of equatorial Pacific conditions during 2014/2015, which is examined in the context of previous ENSO events.