. Compendium of meteorology. Meteorology. 9 10 II 12 13 14 16 16 17 IS 19 ZO PERIOD OF SWELL,Tp,IN SECONDS. 9 10 M 12 13 14 15 16 17 PERIOD OF SWELL,T;,,IN SECONDS 8 19 ZO Fig. 2.—Distance from which swell comes, travel time, and wind velocity in generating area as functions of observed height and period of swell. The upper figure is drawn for a long-lived storm, the lower figure for a short-lived storm. The assumed relation between wind speed and duration for these two cases is shown in the inset. (From Sverdrup and Munk [16].) as a typical maximum period for the swell. The corre- sponding gr
. Compendium of meteorology. Meteorology. 9 10 II 12 13 14 16 16 17 IS 19 ZO PERIOD OF SWELL,Tp,IN SECONDS. 9 10 M 12 13 14 15 16 17 PERIOD OF SWELL,T;,,IN SECONDS 8 19 ZO Fig. 2.—Distance from which swell comes, travel time, and wind velocity in generating area as functions of observed height and period of swell. The upper figure is drawn for a long-lived storm, the lower figure for a short-lived storm. The assumed relation between wind speed and duration for these two cases is shown in the inset. (From Sverdrup and Munk [16].) as a typical maximum period for the swell. The corre- sponding group velocities with which the disturbance created by a storm is effectively propagated by surface wave motion are of the order of 900 nautical miles per Table I. Sample Calculations for a Storm of Unusual Duration (Case A) and a Short-lived Storm (Case B) (ft) Csec) Storm duration Isee inset, Fig. 2) D (naut. mi) 'd (hr) U (knots) 6 12 Case A 700 38 30 CaseB 825 45 45 day for the forerunners, in constrast with 400 miles per day for the swell. A second advantage of the "frequency-spectrum method" over the "height-period method" is that travel time and storm distance are uniquely determined from a knowledge of wave periods. The need for measuring wave height is eliminated. Instrumentation. Shore-based instruments for record- ing ocean waves have been in existence for many Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original American Meteorological Society. Committee on the Compendium of Meteorology; Malone, Thomas F. Boston : American Meteorological Society
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