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

Abstract

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 large-scale 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.

The Benefits of Global High Resolution for Climate Simulation: Process Understanding and the Enabling of Stakeholder Decisions at the Regional Scale

“…However, it has required deployment of models with sufficient resolution in both the atmosphere and ocean in order to study and understand such interactions at the process level Chelton and Xie 2010;Kwon et al 2010;J. Ma et al 2015;Ma et al 2017). …”

“…For example, the salient feature of the Gulf Stream rainband (Minobe et al 2008) is captured by an atmospheric GCM of about 50-km grid spacing (Minobe et al 2008;Kuwano-Yoshida et al 2010;Scher et al 2017). By direct comparisons between high-resolution and lowresolution regional atmospheric model simulations (Willison et al 2013;Ma et al 2017;Hawcroft et al 2017), it is shown that latent heat release associated with extratropical cyclone development is fundamentally important for realistic winter storm simulations, and it is only when the model has sufficient resolution to resolve small-scale diabatic heating that the full effect of mesoscale air-sea interactions on extratropical cyclogenesis can be correctly simulated.…”

“…A particularly useful experimental strategy for this type of study is a set of twin atmospheric model simulations, one of which is forced by observed SSTs and the other by spatially smoothed SSTs (Xie et al 2002;Minobe et al 2008;Kuwano-Yoshida et al 2010;Small et al 2014b;Piazza et al 2016;X. Ma et al 2015X.…”

“…These studies reveal how finescale ocean features influence storm density (Minobe et al 2008;Piazza et al 2016), fronts (Masunaga et al 2015;Parfitt et al 2016), jet stream shifts (Piazza et al 2016;X. Ma et al 2015X. Ma et al , 2017O'Reilly et al 2017), storm-track strength (Small et al 2014b), and remote rainfall response along the U.S. West Coast to Kuroshio eddies (X.…”

“…Ma et al , 2017O'Reilly et al 2017), storm-track strength (Small et al 2014b), and remote rainfall response along the U.S. West Coast to Kuroshio eddies (X. Ma et al , 2017; Kuwano-Yoshida and Minobe 2017).…”