Simulation of a Typical Dry Summer Condition. As an example of illustrating the integrated model’s ability to simulate hydrodynamics and salinity distribution within the Barataria Basin, a typical dry summer condition was chosen to be simulated. This relatively dry season was selected in order to reduce the noise to signal ratio that might confound the impacts of freshwater diversions. Specifically, using the observed sea level height and salinity estimated at the open boundary, observed wind and precipitation, and estimated evaporation as forcing, model simulation was carried out for a 30-day period from July 7 to August 5, 1999. Figure 2-1 shows the locations of relevant stations. During this period, total precipitation was 6.8 cm (Figure 2-2), which is only half of the long-term average of 15 cm. Evaporation, however, totaled 11.8 cm for the 30 days of the simulation (Figure 2-2). This simulation period represents typical, environmentally fair, summer conditions of predominantly northerly or southerly breezes of 3 to 7 m s −1 with occasional shifts in wind direction (Figure 2-3). It should be noted that the wind directions during the first half of the simulation period show primarily southerly breezes except between the 6th and 8th days and that the southerly breezes are still modulated by the land-sea breeze system. During the last 12 days, however, the directions change by day and night due to the temperature differences between land and sea. The most pronounced effect of wind forcing on the Gulf of Mexico systems is the difference between a northerly and a southerly wind (Xxxxxxx and Xxxxxx, 1998). In order to delineate relationships between the local wind and water level, approximately four months (4/1/1999-7/30/1999) of hourly records of water level and wind data from GDIL1 were used to estimate the spectral density of water level and wind components. The coherence between water level and wind components was estimated by averaging over 30 frequencies, giving 60 degrees of freedom with a 95% significance level of 0.098 (Figure 2-4). It was found that the coherence between water level and each wind component was frequency dependent. The significant energy peak is at very low frequency, roughly less than 0.01 cph. At short sub-tidal time scales (a few days), the along-estuary wind stress drives an estuarine-shelf exchange; at longer time scales Ekman convergence/divergence driven by alongshore wind stress drives the estuarine-shelf exchange (Xxxxxxxxx and Xxxxxxx, 1986). Kjerfve (1975), based on ...
