National Science Foundation, Division of Ocean Science, Physical Oceanography
Regional Coupled Ocean-Atmosphere Feedback Processes
Affecting Climate Along the California Coast
Arthur J. Miller and Joel R. Norris
Award: $652,000
Duration: 2010-2015
Collaborator: Hyodae Seo (Woods Hole Oceanographic Institution)
Project Summary.
Recent satellite observations have revealed that mesoscale sea surface temperature (SST) anomalies perturb the atmospheric boundary layer (ABL) by altering its stability and its consequent vertical transport of momentum and heat. It remains unclear, however, how strongly these mesoscale flux anomalies affect the mean and transient flows in both the atmosphere and ocean. Long-term simulations with a realistic coupled ocean-atmosphere model that resolves oceanic mesoscale, the ocean-driven surface fluxes, and the associated ABL and tropospheric response are needed to better understand the effects of these feedbacks.
We propose a research effort that will use coupled and uncoupled model runs in conjunction with observations to address several key issues in mesoscale ocean-atmosphere interaction in the California Regional Sector including:
- What are the local effects of mesoscale ocean-atmosphere coupling on the cloud cover and atmospheric flow along the California Coast?
- What are the remote effects of mesoscale ocean-atmosphere coupling on the fine-scale atmospheric circulation, rainfall patterns, snowfall patterns and land-surface processes along the coastal, in the central valleys, and over the interior mountain regions of California?
- What are the effects of mesoscale ocean-atmosphere coupling on the evolution of coastal upwelling frontal structures along the California Coast?
We propose to investigate these feedback effects using a high-resolution regional coupled ocean model (SCOAR) that couples the Regional Ocean Modeling System (ROMS) to the Regional Special Model (RSM). Coupled and uncoupled runs of downscaled large-scale atmospheric reanalysis fields will be compared side-by-side to assess the effects of mesoscale surface flux anomalies on the ABL, overlying tropospheric flows and oceanic upwelling frontal flows. We propose to apply a new strategy by running the coupled model in coupled mode, but with mesoscale SST variations spatially smoothed to remove ocean mesoscales in the coupler (only) to unambiguously identify the impact of the ocean mesoscale on the atmospheric circulation. Extensive physical diagnostics and observational comparisons will further elucidate the processes that link the mesoscale feedbacks to the local and remote atmospheric and oceanic responses.
Improved understanding of the impacts of mesoscale atmosphere-ocean coupling will form the foundation for determining likely changes induced by global warming on the regional climate of California and its coastal ocean. This research is also relevant to climate predictability, regional response to global warming, water resource usage, and energy usage and marine ecosystem response to climate variability.