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3.2 Surface Wave Climatology 



This section presents meteorological and surface wave data from NOAA buoy 44007 

 during the period from January 1993 through May 1996. In the discussion which follows, 

 emphasis is placed on wave climatology and the frequency of major storms, as the main 

 objective of this project was to determine whether storm waves can generate significant near- 

 bottom currents and resuspension of bottom sediments at PDS. It is well known that major 

 coastal storms can cause significant perturbations in the internal pressure field of the coastal 

 ocean and intensified, low-frequency currents as a result of this pressure adjustment; 

 discussion of storm-generated currents is presented in Section 3.3. 



3.2.1 Time Series of Meteorological Observations 



The meteorology along the coast of Maine is seasonally dependent, as reflected by 

 winds, atmospheric pressure fluctuations, surface waves, and water temperature. To 

 illustrate this seasonal variability, Figures 3-3a through 3-3c present annual time series of 

 meteorological and oceanographic conditions measured by NOAA buoy 44007 during 1993, 

 1994 and 1995, respectively. The most noticeable characteristic of these time series plots is 

 the annual cycle of sea surface temperature (next-to-lowest tier in figures), ranging from a 

 minimum of roughly 1 °C in March to a maximum approaching 20 °C in July. Short-term 

 temperature fluctuations on the order of a few degrees are observed in summer months, 

 probably as a result of diurnal heating and strong temperature stratification in the near- 

 surface waters. In contrast, surface water temperatures vary minimally on time scales of 

 hours to days during fall and winter on account of intense vertical mixing and creation of a 

 relatively thick isothermal layer at the surface. 



Surface waves in the vicinity of PDS (middle two tiers in Figures 3-3a through 3-3c) 

 are largest in fall and winter as a result of storms which normally have durations of a few 

 days. For example, in 1993 ten events having significant wave heights in excess of 4 m were 

 encountered during February-March and during December 1993-January 1994 (Figure 3-3a). 

 Fewer storms having waves in excess of 4 m were observed in 1994 and 1995 (Figures 3-3b 

 and 3-3c, respectively) but all occurred during fall or winter. Wave periods (presented as the 

 period of the most dominant wave in the wave spectra for a given measurement) were 

 generally between 4 and 12 sec, but longer periods were sometimes encountered. 



Atmospheric pressure data (lowest tier in Figures 3-3a through 3-3c) reveal larger and 

 more frequent fluctuations during fall and winter, in concert with major fluctuations in wave 

 height and wind speed that were associated with the passage of storms. 



Oceanographic Measurements at the Portland Disposal Site during Spring of 1996 



