Impact of the midlatitude storm track on the upper Pacific Ocean

Transient eddies in the atmosphere induce a poleward transport of heat and moisture. A moist static energy budget of the surface layer is determined f rom the NCEP reanalysis data to evaluate the impact of the storm track. It is found that the transient eddies induce a cooling and drying of the surfa ce layer with a monthly mean maximum of 60 W m(-2). The cooling in the midl atitudes extends zonally over the entire basin. The impact of this cooling and drying on surface heat fluxes, sea surface temperature (SST), water mas s transformation, and vertical structure of the Pacific is investigated usi ng an ocean model coupled to an atmospheric mixed layer model. The cooling by atmospheric storms is represented by adding an eddy-induced transfer vel ocity to the mean velocity in an atmospheric mixed layer model. This is bas ed on a parameterization of tracer transport by eddies in the ocean. When t he atmospheric mixed layer model is coupled to an ocean model, realistic SS Ts are simulated. The SST is up to 3 K lower due to the cooling by storms. The additional cooling leads to enhanced transformation rates of water mass es in the midlatitudes. The enhanced shallow overturning cells affect even tropical regions. Together with realistic SST and deep winter mixed layer d epths, this leads to formation of homogeneous water masses in the upper Nor th Pacific, in accordance to observations.