The Bjerknes Centre is a collaboration on climate research, between the University of Bergen, NORCE, the Institute of Marine Research, Nansen Environmental and Remote Sensing Centre.

Seminar talk: Role of Stochastic Atmospheric Forcing in Tropical Pacific Decadal Variability and ENSO Modulation

Tianyi Sun from University of Texas at Austin will give a seminar talk on April 3.

Tanyi Sun
Tianyi Sun

Short biography:

I'm a PhD candidate at University of Texas Institute for Geophysics, working with Dr. Yuko Okumura. My research focuses on the interdecadal climate variability of the tropical Pacific and its interactions with El Nino-Southern Oscillation.

Abstract:

The analysis of a millennium-long control simulation of the Community Climate System Model version 4 (CCSM4) shows that the amplitude and other properties of the El Niño-Southern Oscillation (ENSO) vary significantly with the leading modes of tropical Pacific decadal variability (TPDV). These modes of TPDV are reproduced to some degree in the atmospheric component of CCSM4 coupled to a slab ocean model, suggesting the role of stochastic atmospheric forcing. To test the hypothesis that TPDV driven by stochastic atmospheric forcing modulates the ENSO, we conducted a set of CCSM4 experiments by imposing surface heat flux anomalies associated with the leading atmospheric modes over the South Pacific, particularly the Pacific-South American (PSA) pattern. The mean state changes resemble the observed interdecadal Pacific oscillation and are accompanied by changes in the relative frequency of El Niño and La Niña events. Preliminary analysis suggests that the occurrence of El Nino and La Nina events are controlled by the sea surface temperature gradient between the tropical Pacific and the other two tropical oceans. When the tropical Pacific is anomalously warm relative to the other two oceans, the associated westerly wind anomalies over the western equatorial Pacific facilitate the development of El Niño events. The opposite condition appears to facilitate the development of La Niña events.

 

Arranged date for the seminar talk: Apr 03, 2019