Intellectual Merit: Recent satellite observations have revealed that mesoscale sea surface temperature (SST) anomalies perturb the atmospheric boundary layer 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 atmospheric boundary layer and tropospheric response are needed to better understand the effects of these feedbacks.
This research effort 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: 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?
These feedback effects will be investigated using a high-resolution regional coupled ocean model that couples the Regional Ocean Modeling System to the Regional Special Model. 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 atmospheric boundary layer, overlying tropospheric flows and oceanic upwelling frontal flows. A new strategy will be applied 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.
Broader Impacts: 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. The results from this research will also be relevant to climate predictability, regional response to global warming, water resource usage, and energy usage and marine ecosystem response to climate variability. A graduate student will be trained in coupled ocean-atmosphere modeling. Both investigators will continue their outreach activities. Dr. Norris is a lead instructor in a UCSD program that provides a month-long hands-on science learning experience to high school students to encourage them to major in engineering or science, and the results of this project will be incorporated into his instruction. Dr. Miller volunteers as a Science Olympiad coach at a local high school.
