기후모형에서 모사한 북태평양 혼합층깊이 평가

Abstract

This study investigates how well the coupled model intercomparison projects phase 3 (CMIP3) models simulate the mixed layer depth (MLD) in the North Pacific Ocean in present climate by comparing outputs from 11 CMIP3 models with MLD climatology based on observational data. The most common biases in winter MLD are a deep bias (about 50 % (120 m) deeper than the observation) in the Kuroshio Extension region (KE) and a shallow bias (about 30 % (80 m) shallower than the observation) in the Oyashio region. The deep bias in the KE is mainly driven by the fact that the simulated KE is too broad and goes too far north. The deep bias is also attributable to the too strong (30 % or greater than observation) midlatitude westeries in CMIP3 models. The shallow bias in the Oyashio region is related with stratification bias in the upper ocean. The pattern correlation between simulated MLDs and observed climatology for the North Pacific Ocean ranges 0.2 ~ 0.7, indicating poor performance of CMIP3 MLD simulation, compared with sea surface temperature and salinity whose pattern correlations are up to 0.9. Our analysis suggests that the CMIP3 climate models show a substantial MLD bias and need significant improvement.