National Science Foundation, Division of Ocean Science, Physical Oceanography
VOCALS: Mesoscale Ocean Dynamical Analysis with Synoptic Data Assimilation and Coupled Ocean-Atmosphere Modeling
Arthur J. Miller
Award: $210,000
Duration: 2008-2011
Project Summary.
The VOCALS observational and modeling program has been designed to address the fundamental dynamics that control the ocean-atmosphere system in the Southeast Pacific (SEP). Large-scale atmospheric subsidence, broad regions of stratocumulus clouds, biogenic and anthropogenic aerosols, cool sea-surface temperature, upwelling ocean boundary currents, and vigorous mesoscale ocean eddies all interact in complicated ways in this region to affect local, basin-scale and global-scale climate variability.
This research focuses on the mesoscale eddies generated in the upwelling regions along the west coast of South America, which affect the distribution of sea-surface temperature (SST) in the SEP in two major ways. Eddy heat fluxes drive SST changes that affect the atmospheric boundary layer (ABL) by altering its stability and consequent heat, momentum and moisture fluxes at the air-sea interface. Eddies also affect nutrient transport, which controls ocean biology and consequent DMS fluxes that create aerosols.
The dynamics of mesoscale ocean eddies will be explored in the two related modeling studies that will aid in the diagnosis of the VOCALS observations and will help us to understand the mechanisms that control the interactions of the variability of the ocean eddy fields, the coastal winds, heat fluxes, and clouds in the VOCALS domain:
1) Observed mesoscale oceanic surveys of the VOCALS campaign will be used in data assimilation experiments (using IROMS) to diagnose the dynamics and sensitivities of the ocean circulation fields. Data assimilation .fits. of the VOCALS hydrographic surveys (and concomitant data) will provide crucial dynamically consistent diagnostics of the circulation for interpreting the relation between physical variables, atmospheric variables and biology. Generalized Stability Analysis will allow the quantitative assessment of sensitivities of model solutions to various parameters, such as upstream ocean forcing, topography, winds, heat fluxes, etc.
2) Large-scale atmospheric forcing fields from NCEP will be downscaled over the VOCALS region, allowing air-sea feedback processes using a regional coupled ocean-atmosphere model (SCOAR) to diagnose the importance of mesoscale air-sea feedbacks during the VOCALS observational period, as well as for key retrospective periods, and to relate the variability of these feedbacks to large-scale climate processes.
This research has broader impacts in that it is relevant to climate predictability associated with ENSO and global warming, both of which are sensitive to accurate simulation of the SEP. The work additionally will result in the education and training for young scientists in the national and international climate community.
This research is also relevant to commercially important SEP fisheries management, which must deal with variations in fish populations and the potential for catastrophic changes due to ENSO variability and changes in circulation due to greenhouse warming