Evaluation of a Coupled Modeling Approach for the Investigation of the
Effects of SST Mesoscale Variability on the Atmosphere
Abstract
This study further evaluates the modeling approach of Jia et al. (2019)
to investigate the potential effects of SST mesoscale variability on the
atmospheric dynamics. The approach employs a global atmospheric
circulation model coupled to a slab ocean model to produce two ensembles
of simulations: one in which the ocean exhibits realistic SST mesoscale
variability, and another in which the SST mesoscale variability is
suppressed. The latter ensemble is produced by spatially filtering the
SST analyses used for the estimation of the oceanic heat flux and the
specification of the SST initial condition. The results of the present
study, which focuses on the processes of the North Pacific, suggest that
while the modeling approach yields the desired SST differences between
the two ensembles at the mesoscales, it also introduces SST differences
at the large scales that become the primary driver of the large scale
differences in the simulated atmospheric flow. Diagnostics based on the
eddy kinetic energy indicate that the large scale differences of the
atmospheric flow lead to major differences in the dynamics of the jet
stream and storm track. Because the large scale SST differences between
the two ensembles are primarily driven by the differences between the
prescribed estimates of the oceanic heat fluxes, finding a proper pair
of those estimates is a necessary condition for the experiment design to
detect the atmospheric response to SST mesoscale variability. The paper
concludes with proposing a new strategy for the estimation of the
oceanic heat fluxes.