North Pacific air-sea flux estimates from a mesoscale atmosphere-ocean circulation model

A main goal of high-resolution coupled ocean-atmosphere numerical simulations is to improve climate predictions at a variety of time and space scales and completeness of the description of surface meteorology and air-sea fluxes. The feedback between sea surface temperature (SST) and ocean surface wind field and its impact on the air-sea flux exchange climatology (and its role in climate change) in the North Pacific is the primary objective of this study using a high-resolution regional climate modeling framework. The atmospheric component of the coupled model is the Weather Research and Forecasting model (WRF Version 3.2). Two different sets of lower boundary conditions are applied at the sea surface: (a) daily mean, interannually varying SSTs estimated by Community Climate System Model Version 3 (CCSM3) with horizontal resolution of 1.4⁰ x 1.4⁰ and (b) daily mean, annually repeating SSTs obtained from a stand-alone Parallel Ocean Program (POP) model simulation with eddy-resolving 0.1⁰ × 0.1⁰ horizontal resolution, driven by the Large and Yeager “Normal Year” atmospheric datasets.

A sensitivity of the multi-year upper-ocean response to the differences between the observed (from field experiments conducted in the Japan Sea during winter 2000, buoys, and QuikSCAT satellite measurements) and the WRF simulated fluxes and wind fields is quantified and examined to understand the importance of the short-lived episodic high-flux events as well as the dynamic transitions of the Kuroshio Extension jet, both of which are important to the dynamics and thermodynamics of the Pacific and coastal climate. Furthermore, sensitivity experiments are conducted with varying horizontal WRF model grid resolutions ranging from 0.1⁰ to 0.3⁰ to obtain a plausible/optimum horizontal grid resolution for future coupled WRF-POP Pacific climate simulations.