Surf’s Up

First, let’s set the mood. (Click the button to play .)

Next, let’s set the scene.

 

That’s right — it’s Monday, and we don’t feel like working, so we’re going to fantasize for a bit about surfing and the freedom of the endless summer that is almost upon us.

This idle day dreaming, to be clear, is prompted by this news report of a series of huge waves that struck Reunion Island in the Indian Ocean (as well as parts of Indonesia, the Maldives, Thailand and Western Australia) on Saturday.

There was no official warning about the freakish waves that killed at least one person, damaged hundreds of homes and displaced thousands of people across Indonesia. Homes and fishing boats were also damaged in Thailand and the Maldives.

Weather officials said the waves were the result of an accumulation of winds in one spot on the ocean, but were looking at why they were so intense.

How do weather officials know where the waves originated? Why, through satellite observation, of course:

The origin and movement of waves reaching up to 11 metres that devastated France’s Reunion Island in the Indian Ocean on Saturday evening have been detected with ESA’s Envisat satellite.

The waves that thrashed the southern port of Saint Pierre, leaving two fishermen missing, causing several piers to collapse and flooding several homes and businesses, originated south of Cape Town, South Africa, and travelled northeast for nearly 4000 km over a period of three days before slamming into Reunion Island.

Dr Bertrand Chapron of IFREMER, the French Research Institute for Exploitation of the Sea, and Dr Fabrice Collard of France’s BOOST Technologies in Brest located and tracked the swells using standard processed Synthetic Aperture Radar (SAR) ESA products…

Chapron and Collard are working on a project that will make data for global swells available to scientists and users by the end of the year as a demonstration. The products will be useful for weather centres to complement the accuracy of their sea forecast models.

Envisat is equipped with an advanced version of the SAR instrument, Advanced Synthetic Aperture Radar (ASAR), flown on the ERS-1 and ERS-2 missions. Its wave mode acquires 10 by 5 km small images, or ‘imagettes’, of the sea surface every 100 km along the satellite orbit. These small ‘imagettes’, which depict the individual wave heights, are then mathematically transformed into averaged-out breakdowns of wave energy and direction, called ocean-wave spectra, which ESA makes available to scientists and weather centres.

A typical SAR satellite images a swath of 400 km, enough to capture complete ‘mesoscale’ phenomena such as tropical storms. While optical satellite images show the swirling cloud-tops of a hurricane, a SAR image pierces through the clouds to show the sea surface roughness and its modulation through the combination of wind wave and currents….

As part of the Global Monitoring for Environment and Security (GMES), a joint initiative of the European Commission and ESA, the space agency has undertaken the development of Sentinel-1, a European polar-orbiting satellite system for the continuation of SAR operational applications. The Sentinel-1 SAR instrument will have a dedicated wave mode allowing the Near Real Time tracking and forecasting of swell for European users. 

No need to wait for the Europeans to get their act fully together, however. Thanks to publicly-available information from the U.S. Navy’s Fleet Numerical Meteorology and Oceanography Center, surfers can already plan their vacations according to where the waves are, dude. Using the WaveWatch III model, FNMOC provides computer-generated models of global wave height and direction (such as this global model).

Proving, as we well know as we sit at our desks this morning daydreaming, that the surf’s up, dude. Somewhere. 

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