The
principal objective of SEAMOS JIP (Joint Industry
Project) is to provide data on meteorological and
oceanographic extreme and operational conditions to
be used in aid of design of offshore structures and
planning of offshore operations in the general area
of the South China Sea (SCS) and immediately contiguous
basins. The study is based upon the hindcast approach,
wherein a series of calibrated numerical models are
applied to calculate the surface winds, ocean surface
waves, storm driven water levels and currents. The
hindcast of a large number of historical storms provides
data from which the climate of extremes is estimated,
while the hindcast of several continuous years provides
the data needed for the estimation of the normal climate.
In
the SCS, relatively extreme surface winds and ocean
response are associated with the southwest (SW) and
northeast (NE) monsoons, typhoons, and combinations
of tropical cyclones and monsoons. 243 historical
events distributed over these various types of storms
were hindcast in SEAMOS. A comprehensive data base
of historical meteorological and oceanographic data
was assembled and used to develop the wind fields
and validate the numerical hindcast models. The approach
used to specify wind fields combined a proven numerical
model of the surface wind field in a tropical cyclone
and classical kinematic analysis techniques to yield
wind fields which are unbiased and as accurate as
possible within the constraints of the available historical
data. The wave field over the SCS is hindcast using
a directional spectral model which resolves the study
domain on a grid of 25 km spacing. A depth integrated
storm surge and current model was used to develop
storm-generated water levels and flow velocities in
the historical storms. The continuous hindcast resolved
the surface wind and wave fields at 50-km resolution
over the 10-year period 1980-1989.
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SEAMOS
has produced comprehensive files of hindcast data
and derivative products. The storm hindcasts provide,
for each of 243 storms, hourly time histories of 20
wind, wave, surge and current variables at over 4000
locations. The continuous hindcasts provide time histories
at 3-hourly intervals over ten years of 17 wind and
wave variables at 259 locations. Return period omnidirectional
extremes of wind speed, wave height, associated wave
period, storm surge and currents are given at 4000
locations for: ( 1) pure monsoon regimes; (2) typhoon
and typhoon/monsoon regimes; (3) the joint regime.
Return period extremes, stratified by wave direction,
are also derived for 25 locations of high interest.
Normals are described at 259 locations in terms of
monthly and annual bivariate and exceedance/non-exceedance
distributions of various surface wind and wave variables.
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