Coupled atmosphere-ocean general circulation models (CGCMs) have systematic errors in the southeast Pacific (SEP) region. The biases need to be traced back to specific model characteristics, such as certain aspect of the physical parameterizations, in order to provide useful guidance on how to improve the model simulation. The primary goal of this proposed study is to improve our understanding of the structure and mechanisms of CGCMs’ systematic biases in the southeast Pacific. To realize this goal, we need to examine, step by step, the key biases in its AGCM, the key biases in its OGCM, and the key biases in its ocean-atmosphere feedback processes when the AGCM and OGCM are coupled together. Therefore, we propose to:
(1) Diagnose the structure and mechanisms of the AGCM biases in stratocumulus/stratus clouds, marine boundary layer (MBL), and surface fluxes in the SEP region in IPCC AR5 CGCMs;
(2) Analyze the upper ocean currents, thermal structures and heat budget in the SEP region in IPCC AR5 CGCMs;
(3) Examine the ocean-atmosphere coupling processes in the SEP region in IPCC AR5 CGCMs, especially how well the ocean-atmosphere feedbacks are simulated; and
(4) Conduct forced OGCM experiments to examine the sensitivity of upper ocean processes to atmospheric forcings relevant to AGCMs’ biases.