2
Wind Wave and Swell
Climate
Sources
Two sources of wind wave and swell information were available to develop
wave climate outside the entrance to Pago Pago Harbor embayment (Table 1).
Both were originally generated for Western Samoa (Kinhill, Riedel & Byrne
1992). No wave information was available directly for the Tutuila coast and
Western Samoa is sufficiently nearby that a similar offshore wave climate can be
expected.
The first source was a nondirectional accelerometer buoy just south of the
Western Samoa Islands. These measurements were collected by the South
Pacific Applied Geoscience Commission for the Government of Western Samoa.
The initial period of deployment was September 1989 to April 1990. The gage
was redeployed in May 1990 to a location 37 km (23 miles) further south. Data
from only the first deployment were available for this study. The gage was
sheltered from the northwest and east but exposed to the northeast through a gap
between islands. The gage had full exposure to waves from east southeast
through west. This exposure, particularly the open southern exposure, is fairly
similar to that for the entrance to Pago Pago Harbor embayment.
The second source of wind wave and swell information was a global hindcast
from which information was saved at a point near Western Samoa. The hindcast
covered the 5-year time period June 1985 to May 1990. Hindcast wave
information was developed by Oceanroutes (Australia) using the Global Spectral
Ocean Wave Model (GSOWM). Since the model grid resolution was 2.5 deg
latitude and longitude, the hindcast includes no representation of small islands
such as the Samoa Islands. Hindcast information near the Samoa Islands
represents deepwater waves in open water at this general location in the Pacific
Ocean. Tutuila is less than one grid cell east and south of this point and the
hindcasts can be considered representative there, as well.
Table 1
Sources for Wave Climate Information
Source
Years
Latitude (deg S)
Longitude (deg W)
Western Samoa buoy
1989-90
13.9
172.2
Global hindcast
1985-90
12.5
172.0
6
Chapter 2 Wind Wave and Swell Climate
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