Envisat Sees Whirling Hurricane Katrina From Ocean Waves To Cloud Tops

SHAKE AND BLOW

Chart showing acquisition locations for Envisat's MERIS and ASAR images. The MERIS image covers approximately 1200 by 1200 km, while the ASAR Wide Swath mode image covers approximately 415 by 1200 km. Image background from CIMSS, Univ. of Wisconsin - Madison. Credits: ESA/Image background from CIMSS, Univ. of Wisconsin - Madison.

More images at ESA

Paris (ESA) Aug 30, 2005
ESA's multi-sensor Envisat satellite has gathered a unique view of Hurricane Katrina in the Gulf of Mexico. While an optical image shows characteristic spiralling cloud patterns, a simultaneous radar observation pierces through the clouds to show how Katrina's 250-kilometre-an-hour an hour winds scour the sea surface.

Envisat simultaneously acquired these images at 1550 UTC (1150 US Eastern Daylight Saving Time) on 28 August, with its Medium Resolution Imaging Spectrometer (MERIS) and Advanced Synthetic Aperture Radar (ASAR).

At the time of acquisition Hurricane Katrina was a maximum Category Five on the Saffir-Simpson scale. Further ESA acquisitions are being prioritised because the International Charter on Space and Major Disasters has been activated.

The eye of the hurricane is seen clearly in both images, with the wall of the eye clearly visible in the MERIS image, the area of the hurricane where the fastest winds and highest rainfall is found.

The ASAR instrument works by recording signal backscatter based on surface roughness: the wind-free storm centre � seen enclosed within a dark ring feature measuring approximately 60 kilometres across - shows up darker because the waters here are hardly rippled by comparison to the sea around it.

Hurricane Katrina, which formed in the Bahamas in mid-August, struck South Florida on 25 August, killing nine people and leaving a million more without electricity. It is poised to strike coastal Louisiana and New Orleans. Hurricane-strength winds of at least 119 kilometres per hour currently extend 136 kilometres from its centre.

Katrina has today dropped from a maximum Category Five to a Category Four storm on the Saffir-Simpson scale, but forecasters warn it could again grow in intensity having made landfall.

With serious flooding anticipated in the hurricane's wake as well as direct storm damage, the US Geological Service (USGS) activated the International Charter on Space and Major Disasters on 27 August.

ESA is a founding member of the Charter, which represents a joint effort by global space agencies to put resources at the service of rescue authorities responding to major natural or man-made disasters. To date the Charter has been activated more than 80 times.

Observing hurricanes

A hurricane is basically a large, powerful storm centred around a zone of extreme low pressure. Strong low-level surface winds and bands of intense precipitation combine strong updrafts and outflows of moist air at higher altitudes, with energy released as rainy thunderstorms.

Envisat carries both optical and radar instruments, enabling researchers to observe high-atmosphere cloud structure and pressure in the visible and infrared spectrum, while at the same time using radar backscatter to measure the roughness of the sea surface and so derive the wind fields just above it.

Those winds converging on the low-pressure eye of the storm are what ultimately determine the spiralling cloud patterns that are characteristic of a hurricane.

Additionally Envisat instruments can potentially be used to take the temperature of the warm ocean waters that power storms during the annual Atlantic hurricane season, or detect sea height anomalies related to warm upper ocean features known as 'loop currents'.

SHAKE AND BLOW

New Orleans Residents Flee Hurricane, Hide In Stadium

New Orleans LA (AFP) Aug 28, 2005
Hundreds of people lugging their worldly goods in plastic trash bags stood Sunday outside a roofed stadium that became a shelter as Hurricane Katrina threatened the city.

Thanks for being here; We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain. With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords. Our news coverage takes time and effort to publish 365 days a year. If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor $5 Billed Once credit card or paypal		SpaceDaily Monthly Supporter $5 Billed Monthly paypal only

The content herein, unless otherwise known to be public domain, are Copyright 1995-2016 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.