Bowen ratio estimates in return flow over the Gulf of Mexico

Abstract

The Bowen ratio (and associated turbulent fluxes at the ocean‐air interface) has been estimated over the Gulf of Mexico's continental shelf. These estimates are time‐averaged values during the outflow phase of a particular return flow event. The study uses standard buoy data and oceanic soundings from the Louisiana‐Texas Shelf Physical Oceanography Program (LATEX). Since the buoys are not equipped with water vapor sensors, the latent heat flux is determined indirectly. The calculation is made possible by combining the buoy data with a one‐dimensional oceanic slab model and climatological estimates of net radiation. The application also requires a locally isothermal ocean. Estimates have been made for the return flow event of November 3–12, 1992, which exhibited maximum ocean‐air temperature differences of ∼10°C. During a 2 day period when the ocean‐air differences were near their maximum and when mixing extended to the seafloor beneath the buoy sites, the Bowen ratio is found to be 0.38±0.06 (0.35±0.08) at buoy sites at depths of 14 (24) m. The corresponding estimates of sensible and latent heat flux are 115±7 (115±7) and 302±48 (329±75) W m−2, respectively. These values compare favorably with results from other field programs that used bulk aerodynamic methods to estimate turbulent fluxes in cold air outflow. The methodology appears to be generally applicable to return flow events in the Gulf of Mexico.