Final Report: Analysis of Water Level, Weather and Acoustic Doppler Profiler Data from Biscayne Bay, Card Sound and Barnes Sound

Smith, Ned; Pitts, Patrick

In early June 1997, the Army Corps of Engineers Waterways Experiment Station (WES) initiated a field study of Biscayne Bay and adjacent waters, including Card Sound, Barnes Sound and Manatee Bay. The field study included the collection of water level data from 12 stations (see Figure 1), acoustic doppler profiler (ADP) data from five stations and weather data from Convoy Point, along the western shore of Biscayne Bay. Recording instrumentation was in place for an approximately one-year period. Station coordinates, starting and ending times are listed in Table 1. The objective of the field study was to collect data that could be used to verify a hydrodynamic model of the Biscayne Bay system. In a June 7, 1999 letter to the National Park Service, Harbor Branch offered to analyze the water level, ADP and weather data within the restricted context of model verification. Following a period of negotiation, Harbor Branch offered a Scope of Work that included screening, editing, analyzing and plotting the data. Specifically, data would be inspected for outliers and gaps. Gaps longer than 12 hours would be considered breaks in the record, and data collected before and after a break would be treated as separate time series. Data would be plotted as time series and presented with expanded captions to aid in the interpretation. Data would be subjected to time series analyses to characterize tidal conditions, and to establish statistically significant associations between wind stress and both water levels and ADP transport. Two reports would be provided. The first would be a Quality Assurance Report that would address the suitability of the data for model verification purposes. The second would be a Final Report to summarize findings directly related to validating model simulations. The Quality Assurance (QA) Report was submitted on September 9, 1999 and again in amended form on February 3, 2000. The QA Report included plots of north-south and east-west wind stress components from the C-MAN Station at Fowey Rocks and from the WES weather station at Convoy Point, plots of the water level data in analog form from each of the twelve stations, plots of the north-south and east-west components of ADP current speed from each of the five stations, a table of the harmonic constants (amplitudes and local phase angles) of the principal tidal constituents, and co-amplitude and co-phase charts of the M2 and N2 tidal constituents. Except for the table of harmonic constants and the co-amplitude and co-phase charts, the emphasis was on analog plots. While analog plots are useful for model validation, the QA Report did little more than repeat what had appeared earlier in the Biscayne Bay Field Data Report (Pratt 1999). The analog plots of current component speed and water level that appear in the Field Data Report provide information that can be compared with model results simulated for the same location and under the same environmental conditions. Such comparisons are qualitative, however, and the acceptance or rejection of the model's ability to reproduce variations in water level and circulation is subjective. In this Final Report, we include analog plots, but we carry the analysis an important step further by presenting results that can be used for a digital approach to model validation. The Final Report focuses on results of harmonic analyses and spectral analyses. Amplitudes and local phase angles resulting from a harmonic analysis of field data can be compared with amplitudes and local phase angles obtained using simulated data from the corresponding part of the model domain. This quantifies the model's ability to reproduce tidal conditions in Biscayne Bay, and it permits comparisons of individual tidal constituents.