Xiaobiao Xu, Yeon S. Chang, Hartmut Peters, Tamay M. Ozgokmen, and Eric P. Chassignet, RSMAS/Univ. of Miami
An entrainment parameterization is developed for isopycnic coordinate models which casts the entrainment into layers as a function of the gradient Richardson number times the velocity difference across layers. The parameters are based on comparing the simulations of generic gravity currents with the HYbrid Coordinate Ocean Model (HYCOM) to reference experiments with the nonhydrostatic, high-resolution, three-dimensional model Nek5000. With this parameterization, HYCOM is able to reproduce the evolution of entrainment in Nek5000 with different forcing, or slope angle. This parameterization is then applied to a realistic configuration of the Mediterranean outflow. The HYCOM results are compared to the observation obtained from the 1988 Gulf of Cadiz Expedition. The comparison shows that HYCOM captures well the localized entrainment where the outflow descends along the continental slope west of the Strait of Gibraltar, and where the water property and volume transport of outflow experience a major modification.