HR: 13:55h
AN: OS43C-02    [Abstracts]
TI: Field and numerical study of entrainment laws for surface mixed layer
AU: Nagashima, H
EM: hidekin@s.kaiyodai.ac.jp
AF: Department of Ocean Sciences, Tokyo University of Marine Science and Technology, Konan 4-5-7 Minato-ku, Tokyo, 108-8477 Japan
AU: * Nagai, T
EM: tnagai@umassd.edu
AF: Physics Department, University of Massachusetts Dartmouth, 285 Old Westport Rd., North Dartmouth, MA 02747 United States
AU: Yamazaki, H
EM: hide@s.kaiyodai.ac.jp
AF: Department of Ocean Sciences, Tokyo University of Marine Science and Technology, Konan 4-5-7 Minato-ku, Tokyo, 108-8477 Japan
AU: Kantha, L H
EM: kantha@colorado.edu
AF: Department of Aerospace Engineering Sciences, CB 431 University of Colorado, University of Colorado CB 431 Boulder, Boulder, CO 80309-0431
AB: Entrainment at the base of mixed layer is a key process that controls climate changes and marine ecosystem. Though many mixed layer models have been developed based on the laboratory results of entrainment and have been evaluated by comparisons with field observation of mixed layer depth and sea surface temperature, there are only few studies to test the empirical entrainment laws found at laboratory. In present study, a steady deepening of the diurnal mixed layer was observed during nocturnal cooling in a large lake. The observed dissipation rates normalized with surface buoyancy flux and wind stress were in good agreement with a previously reported value. We simulated the observed time series of the water column using the Mellor-Yamada second order turbulence closure scheme. The time series of the observed diurnal mixing layer depth agreed well with the simulated time series. The details of entrainment were investigated using both data sets. Because the deepening was due to both cooling and wind stress, the entrainment was separated into two parts. Each part followed the empirical relationships reported from laboratory studies. In order to use both forcings, namely convection and wind stress, we propose a new entrainment diagram taking both factors into consideration.
DE: 4227 Diurnal, seasonal, and annual cycles
DE: 4239 Limnology
DE: 4568 Turbulence, diffusion, and mixing processes
DE: 4572 Upper ocean processes
DE: 3307 Boundary layer processes
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting