HR: 0800h
AN: H41F-0345    [Abstracts]
TI: Modelling Thermal Structure and Vertical Eddy Diffusivity in Ponds With the Princeton Ocean Model
AU: * Branco, B F
EM: brett.branco@uconn.edu
AF: University of Connecticut, Department of Marine Sciences, 1080 Shennecossett Road, Groton, CT 06340-6097 United States
AU: Torgersen, T
EM: thomas.torgersen@uconn.edu
AF: University of Connecticut, Department of Marine Sciences, 1080 Shennecossett Road, Groton, CT 06340-6097 United States
AB: Observations of the vertical thermal and chemical structure in a shallow pond reveal that the rate of vertical transport varies significantly on the centimeter space scale and the subhourly timescale. The rates of vertical transport must be quantified on the appropriate time and space scale to understand the coupled physical and chemical dynamics of shallow (maximum depth of a few meters) aquatic systems. Empirical formulas do not exist for vertical eddy diffusivity in shallow systems where shear and density gradients are dynamic. Therefore, the Princeton Ocean Model was adapted for use in shallow systems in order to determine the vertical eddy diffusivity for use in future biogeochemical reaction and transport modelling. The heat flux terms were determined from local meteorological conditions and published bulk formulations. An open boundary condition for heat was added to the bottom to account for heat exchange with the sediments. The incident short wave radiation was divided into seven bandwidths with different attenuation coefficients. Model temperature generally agreed with data from Mirror Lake (Storrs, CT; max depth = 1.5 meters) over a range of weather conditions and measured visible light attenuation coefficients. The modeled vertical diffusivity for heat varied over five orders of magnitude. The transition from molecular diffusivity to complete turbulent mixing occurs on the hourly time scale and the cm space scale. During the modeled time periods, wind speeds are generally negligible at night when the water column mixed depth increases due to convective overturn. The magnitude of the thermal stratification is a strong function of the visible light attenuation coefficient. The Princeton Ocean Model can be applied to examine diel stratification/destratification dynamics and the subsequent effects on the biogeochemistry of shallow aquatic systems.
DE: 4227 Diurnal, seasonal, and annual cycles
DE: 4255 Numerical modeling
DE: 4568 Turbulence, diffusion, and mixing processes
DE: 1845 Limnology
DE: 1871 Surface water quality
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting