P4.6
The lake-atmosphere turbulent exchanges (LATEX) field measurement campaign
Elie Bou-Zeid, Princeton University, Princeton, NJ; and N. Vercauteren, U. Lemmin, H. Huwald, and M. B. Parlange
Understanding and quantifying the interaction of the atmosphere with underlying water surfaces is of great importance for a wide range of scientific fields such as water resources management, climate studies of ocean-atmosphere exchange and regional weather in coastal areas. However, atmospheric dynamics over water surfaces have generally received less attention than land-atmosphere interactions, partially due to logistical difficulties in operating in-situ field studies. The Lake-Atmosphere Turbulent EXchanges (LATEX) field measurement was designed to address the issues of air-water interactions over lakes. The experiment, which was performed over Lake Geneva (Switzerland) on a 10 meter high tower situated 100 meters offshore, allows the study of a relatively simple case of atmosphere-water interaction where the effect of the waves on atmospheric turbulence is minimal and the dynamics of the air-water interactions are mainly atmosphere-driven.
The main instrumentation consisted of four sonic anemometers and four open path gas analyzers measuring wind speed, temperature, and humidity at 20 Hz. The four pairs were setup as a vertical array. Additional supporting measurements included net radiation, water surface temperature, relative humidity and temperature of air, wave height and speed, as well as several point-measurements of air and water temperature.
The diurnal trends of momentum, heat, and water vapor fluxes for the whole experimental period are presented and several evaporation models of varying complexity tested. Evaporation models based on energy balance are found to perform quite well. The roughness lengths of the surface (for momentum, heat, and water vapor) are also investigated. The focus is then turned to the coherent structures over the lake and results from a quadrant analysis for momentum, heat and water vapor fluxes are analyzed. Under neutral and stable stratification, ejections and sweeps contribute equally to the vertical fluxes; as the atmospheric boundary layer turns to unstable, ejections begin to clearly dominate.
Poster Session 4, POSTERS: Small-Scale Studies
Wednesday, 14 January 2009, 2:30 PM-4:00 PM, Hall 5
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