NSFGEO-NERC:Large-Scale Atmospheric Circulation Response to Oyashio Extension Frontal Variability

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This joint proposal to U.S. National Science Foundation's Directorate for Geosciences and U.K. NaturalEnvironment Research Council aims to investigate how the Oyashio Extension frontal variability in theNorthwest Pacific Ocean influences the large-scale atmospheric circulation by accumulating theinteraction between the individual weather system and underlying ocean front. The atmospheric stormtrack exhibits the local maximum strength in the Northwest Pacific over the strong ocean fronts driven bycollocated maximum baroclinicity, which is in turn maintained by huge heat and moisture supplied by theocean. While significant advances have been achieved in the past decade or so on our understanding ofocean front's impact on the atmosphere for the mean climate, there are still many crucial questions yet tobe answered, especially related to impact of ocean frontal variability on the atmospheric circulationvariability. A particular goal of this proposal is to unveil the link between the local air-sea interaction inweather scale near the Oyashio Extension and its cumulative impact on the large-scale atmosphericcirculation and climate variability. Specific emphases will be placed on the seasonality of this link bycontrasting the early and late winter, and also the asymmetry/nonlinearity in the large-scale atmosphericresponse to warm and cold SST anomalies induced by a shift of the Oyashio Extension front to the northand south, respectively. These challenging goals will be addressed by combining analyses ofobservational and reanalysis datasets and targeted climate model experiments using the VariableResolution Community Atmosphere Model v.6 with Spectral Element dynamical-core, a state-of-the artatmospheric general circulation model, which will be configured with a very high-resolution over theNorth Pacific and lower resolution elsewhere globally to realistically simulate the frontal air-seainteraction over the Oyashio Extension as well as the feedback with the large-scale circulation at amanageable computational cost. Furthermore, the role of local ocean coupling will be investigated bycomparing the atmosphere-only simulations with those coupled to the 1-dimensional column oceanmodel.