Importance of Resolving Kuroshio Front and Eddy Influence in Simulating the North Pacific Storm Track

Local and remote atmospheric responses to mesoscale SST anomalies associated with the oceanic front and eddies in the Kuroshio Extension region ( KER) are studied using high- ( 27 km) and low- resolution ( 162 km) regional climate model simulations in the North Pacific. In the high- resolution simulations, removal of mesoscale SST anomalies in the KER leads to not only a local reduction in cyclogenesis but also a remote largescale equivalent barotropic response with a southward shift of the downstream storm track and jet stream in the eastern North Pacific. In the low- resolution simulations, no such significant remote response is found when mesoscale SST anomalies are removed. The difference between the high- and low- resolution model simulated atmospheric responses is attributed to the effect of mesoscale SST variability on cyclogenesis through moist baroclinic instability. It is only when the model has sufficient resolution to resolve small- scale diabatic heating that the full effect of mesoscale SST forcing on the storm track can be correctly simulated.