Regional atmospheric simulation of monthly precipitation using high-resolution SST obtained from an ocean assimilation model: Application to the wintertime Japan sea

The present study examines the influence of an assimilation SST product on simulated monthly precipitation. The high-resolution SST structures located close to the oceanic front and coastal areas are important in regional atmospheric simulations over semienclosed marginal seas such as the Japan Sea. Two simulations are conducted using assimilation and interpolation SST products (experiments R and N, respectively), for January 2005. The surface heat fluxes and PBL height in experiment R are lower than those in experiment N in coastal areas and the cold tongue. A decrease of 4 K in SST leads to decreases of 120 W m^-2 in surface sensible and latent fluxes and 300 m in PBL height. The precipitation in experiment R is less than that in experiment N for the sea area except at 38°N, 137°E. The cold tongue in the central Japan Sea acts to reduce moisture supply via the latent heat flux, resulting in low precipitation in coastal areas. The fact that the difference between observed and modeled precipitation in experiment R is 21% less than that in experiment N demonstrates that the assimilation of SST data leads to improved regional atmospheric simulations of monthly precipitation.