EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Tropical Instability Waves in a High-Resolution Oceanic and Coupled GCM

Li Tianyan1,2 and Yu Yongqiang1,2
Li Tianyan and Yu Yongqiang
  • 1Institute of Atmospheric Physics, Chinese Academy of Sciences, No. 40 Huayanli, Beichen West Road, Chaoyang District, P. O. Box 9804, Beijing 100029, P. R. China (
  • 2University of Chinese Academy of Sciences, No.1 Yanqihu East Road, Huairou District, Beijing 101408, P.R.China

Tropical instability waves (TIWs) are the dominant mesoscale variability in the eastern equatorial Pacific Ocean. TIWs have direct impacts on the local hydrology, biochemistry and atmospheric boundary layer, and feedback on ocean circulations and climate variability. In this study, the basic characteristics of Pacific Ocean TIWs simulated by an eddy-resolving ocean model and a coupled general circulation model are evaluated. The simulated TIW biases mainly result from the mean climatology state, as TIWs extract eddy energy from the mean potential and kinetic energy. Both the oceanic and coupled models reproduce the observed westward propagating large-scale Rossby waves between approximately 2-8N, but the simulated TIWs have shorter wavelengths than the observed waves due to the shallower thermocline. Meanwhile, the weak meridional shears of background zonal currents and the less-tilted pycnocline in these two models compared to the observations causes weak barotropic and baroclinic instability, which decreases the intensity of the simulated TIWs. We then contrast the TIWs from these two models and identify the roles of atmospheric feedback in modulating TIWs. The latent heat flux feedback is similar to observation in the coupled model but absent in the ocean model, contributing to the stronger standard deviation (STD) of the TIW SST in the ocean model. The ocean model is not able to capture realistic air-sea interaction processes when forced with prescribed atmospheric forcing. However, the misrepresented atmospheric feedback in the ocean model tends to decrease the sea surface height (SSH) variability, and the current feedback damping effect is stronger in the ocean model than in the coupled model. Combined with weaker barotropic conversion rate and baroclinic conversion rate in the ocean model than in the coupled model, the STD of the TIW SSH in the ocean model is weaker.

How to cite: Tianyan, L. and Yongqiang, Y.: Tropical Instability Waves in a High-Resolution Oceanic and Coupled GCM, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1773,, 2023.