The Full Picture

More recently a storm surge on the South African east coast

resulted in damage totalling hundreds of millions of rands.

Furthermore, ongoing financial loss is being experienced by the large

tourist industry because the exposed coastline continues to lose sedi-

ment. Although fixed structures obviously cannot be moved, much

of the property loss could have been prevented if there had been

sufficient warning to enable residents to relocate movable objects.

An ocean model run in hindcast mode can calculate the long-term

likelihood of such an event, providing coastal authorities with advice

on reasonable limits to coastal development.

Despite the drive to move away from fossil fuels, the fact is that the

oil and gas industry continues to explore for new offshore reserves

in increasingly deeper water. Ocean prediction models will be called

upon to ensure that these new developments do not threaten the

sustainability of other activities in the region. One of the major

requirements is a need for ocean current information throughout the

water column. Off the southern coast of Namibia is one of the richest

offshore

diamond

fields in the world. Numerical ocean modelling

supported by data from the GEOSS network and also any additional

locally-collected information, would help to predict more accurately

the effects of new developments on the environment, as well as to

optimize operations in the high wave energy environment.

Coastal populations are rising rapidly and Cape Town is no excep-

tion, with the municipal population rising by over 15 per cent in the

past decade. This puts increasing pressure on the coastal environ-

ment, particularly when it comes to getting rid of sewage and waste

products from industry. Outfall pipes need to be designed to with-

stand the heaviest wave and current conditions. In the

latter case particularly, actual data is usually very sparse

and consists of short records. The only way to generate

sufficient data for design purposes is to model the circu-

lation and then run the model in hindcast mode. In May

1984 a very intense low-pressure system southwest of

Cape Town resulted in significant wave heights of over

ten metres, which caused one of the City’s main outfall

pipes to rupture.

The role of the smaller maritime NMS in GEOSS

and ocean prediction systems

National Meteorological Services with limited resources

cannot be expected to run their own ocean models and

indeed there should be no need for them to do so. The

resolution of global models is ever-improving as

computing power increases and it is generally accepted

that ocean prediction, like GEOSS, is a global partner-

ship. Smaller NMS are not in a position to contribute to

extremely expensive satellite programs. Where they can

still play a significant role however, is the collection of

quality marine data in their own waters, and by ensur-

ing that they maintain close contact with their

international community. Even ocean data which is not

available real-time can still perform a vital role by

providing verification data for the models, especially in

data-sparse waters.

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The FPSO (floating production storage offloading) platform

Dalia

. Cables parted in rough seas off the South African coast as the newly built 300 metre

vessel was being towed to Angola

Photo: Sydney Marais, South African Weather Service

GEOSS C

OMPONENTS

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REDICTION

YSTEMS