Interannual variability and dynamics of intraseasonal wind rectification in the equatorial Pacific Ocean
The rectification of intraseasonal wind forcing on interannual sea surface temperature anomalies (SSTA) and sea level anomalies (SLA) associated with El Niño–Southern Oscillation (ENSO) during 1993–2016 are investigated using the LICOM ocean general circulation model forced with daily winds. The comparisons of the experiments with and without the intraseasonal wind forcing have shown that the rectified interannual SSTA and SLA by the intraseasonal winds are much weaker than the total interannual SSTA and SLA in the cold tongue, due to the much weaker rectified than the total interannual Kelvin and Rossby waves in the equatorial Pacific Ocean. The dynamics of the rectification are through the nonlinear zonal and vertical advection by the background currents, which produces downwelling equatorial Kelvin waves during El Niño. The meridional advection is much smaller than the zonal and vertical advection, suggesting that the rectification is not induced by the Ekman dynamics or the thermocline rectification. The rectified interannual Kelvin waves are found to be much smaller than reflected at the Pacific western boundary and those forced by the interannual winds, suggesting that the latter two play a much more important role in ENSO dynamics than the intraseasonal winds. The results of this study suggest an unlikely significant role of oceanic nonlinear rectification by intraseasonal winds during the onset and cycling of El Niño.
KeywordsIntraseasonal rectification Interannual variability ENSO Kelvin and Rossby waves Nonlinear oceanic dynamics
This work was supported jointly by NSFC (41421005, 41375094, 41406028, 41720104008, 41776011), QMSNL (2016ASKJ12), CAS (XDA11010102, XDA11010205), and the Shandong Provincial projects (U1406401). We thank the Aviso project, Hadley Center, and NCEP for sharing their data.
- Hu S, Fedorov AV (2016) Exceptionally strong easterly wind burst stalling El Niño of 2014. (EARTH, ATMOSPHERIC AND PLANETARY SCIENCES) (Report). In: Proceedings of the National Academy of Sciences of the United States, vol 113(8), 2005Google Scholar
- Large WG, Yeager SG (2004) Diurnal to decadal global forcing for ocean and sea-ice models—the data sets and flux climatologies NCAR Technical Note NCAR/TN-460 + STRGoogle Scholar
- Lengaigne M, Boulanger JP, Menkes C, Delecluse P, Slingo J (2004b) Westerly wind events in the tropical Pacific and their influence on the coupled ocean–atmosphere system: a review. In: Wang C, Xie SP, Carton JA (eds) Earth’s climate: the ocean–atmosphere interaction. Geophys Monogr Ser, vol 147. AGU, Washington, D. C, pp 49–69Google Scholar
- Levitus S, Boyer TP (1994) World Ocean Atlas 1994 Volume 4: Temperature. NOAA Atlas NESDIS 4. U.S. Department of Commerce, Washington, DC, p 117Google Scholar
- Levitus S, Burgett R Boyer TP (1994). World Ocean Atlas 1994 Volume 3: Salinity. NOAA Atlas NESDIS 3. U.S. Department of Commerce, Washington, DC, p 99Google Scholar
- Liu H, Yu Y, Li W, Zhang X (2004) LASG/IAP climate system ocean model (LICOM1.0), User manual (in Chinese). Science Publication, Washington, DCGoogle Scholar
- Packnowski RC, Philander SGH (1981) Parameterization of vertical mixing in numerical models of the tropical ocean. J Phys Oceanogr 11:1442–1451Google Scholar
- Slingo J, Rowell DF, Sperber KR, Nortley F (1999) On the predictability of interannual behavior of the Madden–Julian Oscillation and its relationship to El Niño. Q J R Meteorol Soc 125:583–609Google Scholar