Characterization of Intraseasonal Kelvin Waves in the Equatorial Pacific Ocean
Abstract
Kelvin waves in the equatorial Pacific Ocean are an important subseasonal modulator of upper‐ocean thermal and kinetic energies. This study develops a methodology for the objective identification of the waves, including their phase and amplitude, that is based on satellite‐derived sea surface height anomalies. Composite analysis of intraseasonal Kelvin waves based on the newly developed index reveals important patterns of wave evolution across the Pacific Ocean. The waves maintain an average phase speed of 2.55 m/s, with maximum of 2.73 m/s when the downwelling portion of the wave is near 150°W and minimum of 2.35 m/s near 175°W. Kelvin waves attain their maximum amplitude at 150°W, the region where intraseasonal surface wind forcing strongly relaxes, and the waves transition from a forced to a freely propagating mode. The dominant processes controlling the mixed‐layer temperature also shift near 150°W. Intraseasonal SST anomalies associated with the waves have maximum amplitude of +/−0.25 °C at 140°W, with much stronger anomalies, +/−1.4 °C, along the thermocline at 155°W. Waves strengthen the eastward equatorial undercurrent by 76% while shifting its maximum 3,500 km to the east. The El Niño Southern Oscillation exerts considerable control over the vigor of Kelvin waves, with statistically significant increases of kinetic energy during El Niño versus La Niña periods. For the benefit of the ocean forecasting community, a counterpart intraseasonal Kelvin wave index is developed that avoids the use of forward time filtering such that wave information is available in real time.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Mar 01, 2019
- Source ID
- 10.1029/2018jc014838
Entities
People
- Adam Rydbeck
- Maria Flatau
- Tommy G. Jensen
Organizations
- Office of Naval Research
- United States Naval Research Laboratory