Meeting Documents

Evaluation of Tropical Instability Waves Activity and Associated Nonlinear Feedbacks on Pacific Climate in Multiple High-Resolution Models and Reanalysis Datasets

Abstract

Tropical instability Waves (TIWs) dominate intraseasonal variability in the tropical Pacific Ocean, and strongly impact tropical ocean dynamics and marine ecosystems as well as modulating tropical climate variability. However, the details of TIW representation in reanalysis datasets remain relatively unexplored. Additionally, most global climate models have been shown to underestimate TIWs and their associated feedbacks due to insufficient horizontal and vertical resolution. Here we evaluate various metrics of TIW activity in ocean reanalysis datasets and TIW-resolving global climate models using in-situ observations and satellite records as baselines. The results show that TIW activity and associated nonlinear heat flux feedback on mean temperature and momentum flux feedback on zonal flow are underestimated in some widely used datasets (ECCO2, GODAS and SODAS) due to the coarse resolutions and systematic biases in background states. This suggests an overestimation of other related physical processes involved in data assimilations. Nevertheless, the high-resolution GLORYS and HYCOM datasets well present the observed spatial and temporal distributions of TIW activity. The high-resolution (0.1 degree) configuration of the Community Earth System Model (CESM) version 1 also effectively captures the TIW variability and their nonlinear interactions with the mean state, cold tongue annual cycle and ENSO. In the Energy Exascale Earth System Model (E3SM) version 1, TIW-related SST variability is overestimated due to the cold tongue bias and TIW-related SSH variability is slightly underestimated. This evaluation provides a concrete outlook on selections of model and reanalysis datasets for representing TIWs and tropical climate.