The Influence of a Resolved Gulf Stream on the Decadal Variability of
Southeast US Rainfall
Abstract
Ocean variability is a dominant source of remote rainfall
predictability, but in many cases the physical mechanisms driving this
predictability are not fully understood. This study examines how ocean
mesoscales (i.e., the Gulf Stream SST front) affect decadal southeast US
(SEUS) rainfall, arguing that the local imprint of large-scale
teleconnections is sensitive to resolved mesoscale features. Based on
global coupled model experiments with eddying and eddy-parameterizing
ocean, we find that a resolved Gulf Stream improves localized rainfall
and remote circulation response in the SEUS. The resolved Gulf Stream
influences the boundary layer, driving a barotropic circulation
response, thus affecting decadal SEUS rainfall due to a westward
extension of the North Atlantic Subtropical High. The
eddy-parameterizing simulation fails to capture the sharp SST gradient
associated with the Gulf Stream and overestimates the role of tropical
SST in the SEUS rainfall due to its classical wintertime connection with
the El Niño/Southern Oscillation.