California Reanalysis Atmosphere-Ocean Coupled Downscaling at 10km

The ocean and atmosphere exchange heat, momentum and masses at the air-sea interface. The sea surface temperature induced heating or cooling alters the atmospheric circulation. The atmospheric circulation modifies the ocean thermal structure and circulation. The local coastal ocean processes such as upwelling are influential to the state of the lower atmosphere along the coast, while the coastal atmospheric circulation, such as sea breeze is influenced by small scale ocean temperature distribution. A high resolution regional ocean atmosphere coupled model is required to research these complex regional coastal ocean atmosphere interactions.

A fully coupled Regional Spectral Model (RSM) and the Regional Oceanic Modeling System (ROMS) suitable for research, downscaling and forecast was developed at the Scripps Institution of Oceanography. The fully coupling is performed by utilizing RSM produced atmospheric forcing and ROMS produced SST. The coupling interval of 24 hours is used. The horizontal resolutions of the atmospheric and oceanic models are set to 10 km. The two models share the same grid.

A series of uncoupled and coupled RSM and ROMS experiments were performed to understand the effect of coupling. In all of our experiments, the ocean and atmosphere boundary conditions are SODA and NCEP/DOE reanalysis, respectively. We will compare in detail, the runs with coupled and uncoupled downscaling, and their impacts on the oceanic and atmosphere state. Main focus is placed on the effect of coupling on the atmospheric analysis along the coast, namely the range of the effect of coastal SST on inland temperature, humidity and circulation.