SPECIAL PUBLICATION NO. 43
levels for the U. S. east coast: 1. strong Table 5. Seasonal range in monthly northwest winter winds blow the water average water levels. away from shore, and 2. water contracts as it cools. He notes that winds re e more Sit No h important in shallow water where tide Yea-s (m) gauges are located, but that contraction u. s. Ewt Comt becomes important in deeper waters.
Swanson (1974) also notes "... seasonal New York 19 0.177 Feb Sep
changes resulting from changes in direct Atlantic City 19 0.165 Feb Sep
changes resulting Baltimore 19 0.238 Feb Sep barometric pressure, steric levels, river Norfolk 19 0.177 Feb Sep discharge, and wind affect the monthly Charleston 19 0.253 Mar Oct variability." Mayport 19 0.314 Mar Oct Miami Beach 17 0.259 Mar Oct
Seasonal variation in tides is usually u. s. CA coast attributed to two harmonic constitutents:
one with a period of one year termed the Key West 19 0.216 Mar Oct solar annual tidal constituent, and the other Cedar Key 10 0.244 Feb Sep Pensacola 19 0.232 Feb Sep
with a period of six months termed the solar Galveston 19 0.247 Jan Sep semiannual constituent (Cole, 1997). Some Port Isabel 4 0.262 Feb Oct consider these to be meteoroligical in nature, U rather than astronomic. However, because u.s. wet coast the root cause of cyclic seasonal weather is Seattle 19 0.159 Aug Dec the changing declination of the sun, they Astoria 19 0.219 Aug Dec should more nearly be astronomical in origin. Cresent City 14 0.180 Apr Dec
Harmonic analysis of the annual tidal record San Francisco 19 0.104 Apr Sep
Harmonic analysis of the annual tidal Los Angeles 19 0.152 Apr Sep can easily determine the amplitude and La Jolla 19 0.143 Apr Sep phase of each of these constituents, thereby San Diego 19 0.152 Apr Sep providing a mathematical definition of the Notes: 1. h = seasonal range based on average of n seasonal variation. (George M. Cole, years of monthly means where monthly means are personal communications.) average of hourly heights; 2. San Diego gauge is located in San Diego Bay; 3. Astoria gauge is located 15
Comparing the closest appropriate miles upstream from the mouth of the Columbia River. curve from Figure 11 to Figures 2 through 5,
it is apparent that the lowest seasonal stand
of mean sea level and, therefore, average occur (e.g., low monthly average mean sea astronomical tide effects occurs when the level wider beaches, and high monthly beach is narrowest for Stinson Beach and average mean sea level narrower beaches) Torrey Pines Beach, California, and Jupiter then a relating parameter needs to be Beach, Florida. For Gleneden Beach, incorporated in the quantifying predictive Oregon, narrow beach widths and monthly relationship(s). It is of consequence to note, average tidal highs seem to be more nearly in for the data of Tables 1 and 4, that the phase. Therefore, it is not clear that seasonal range of monthly average mean sea seasonal changes in astronomical tides level is from 9 to 33% of the mean range of significantly affect seasonal shoreline tide (hmrt). variability, at least not in terms of average monthly measures. Quite clearly, however, APPLICATION OF RESULTS such data needs to be procured for each site to confirm a correlation or lack thereof. While horizontal shoreline shift (or Should the proper correlation consistently beach width change) addresses only one
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