Featured Research

from universities, journals, and other organizations

Envisat Sees Whirling Hurricane Katrina From Ocean Waves To Cloud Tops

August 30, 2005
European Space Agency
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.

Two separate views of Hurricane Katrina acquired 28 August 2005 from instruments aboard Envisat. The ASAR Wide Swath mode radar image of the sea surface shows how Katrina's wind fields are rippling the ocean. Beside it is the MERIS Reduced Resolution mode optical images showing characteristic swirling cloud patterns around the central eye, with the eye walls visible.
Credit: ESA

Atthe time of acquisition Hurricane Katrina was a maximum Category Fiveon the Saffir-Simpson scale. Further ESA acquisitions are beingprioritised because the International Charter on Space and MajorDisasters has been activated.

The eye of the hurricane is seenclearly in both images, with the wall of the eye clearly visible in theMERIS image, the area of the hurricane where the fastest winds andhighest rainfall is found.

The ASAR instrument works by recordingsignal backscatter based on surface roughness: the wind-free stormcentre – seen enclosed within a dark ring feature measuringapproximately 60 kilometres across - shows up darker because the watershere are hardly rippled by comparison to the sea around it.

HurricaneKatrina, which formed in the Bahamas in mid-August, struck SouthFlorida on 25 August, killing nine people and leaving a million morewithout electricity. It is poised to strike coastal Louisiana and NewOrleans. Hurricane-strength winds of at least 119 kilometres per hourcurrently extend 136 kilometres from its centre.

Katrina hastoday dropped from a maximum Category Five to a Category Four storm onthe Saffir-Simpson scale, but forecasters warn it could again grow inintensity having made landfall.

With serious flooding anticipatedin the hurricane's wake as well as direct storm damage, the USGeological Service (USGS) activated the International Charter on Spaceand Major Disasters on 27 August.

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

Observing hurricanes

Ahurricane is basically a large, powerful storm centred around a zone ofextreme low pressure. Strong low-level surface winds and bands ofintense precipitation combine strong updrafts and outflows of moist airat higher altitudes, with energy released as rainy thunderstorms.

Envisatcarries both optical and radar instruments, enabling researchers toobserve high-atmosphere cloud structure and pressure in the visible andinfrared spectrum, while at the same time using radar backscatter tomeasure the roughness of the sea surface and so derive the wind fieldsjust above it.
Those winds converging on the low-pressure eye of thestorm are what ultimately determine the spiralling cloud patterns thatare characteristic of a hurricane.

Additionally Envisatinstruments can potentially be used to take the temperature of the warmocean waters that power storms during the annual Atlantic hurricaneseason, or detect sea height anomalies related to warm upper oceanfeatures known as 'loop currents'.

Story Source:

The above story is based on materials provided by European Space Agency. Note: Materials may be edited for content and length.

Cite This Page:

European Space Agency. "Envisat Sees Whirling Hurricane Katrina From Ocean Waves To Cloud Tops." ScienceDaily. ScienceDaily, 30 August 2005. <www.sciencedaily.com/releases/2005/08/050830071214.htm>.
European Space Agency. (2005, August 30). Envisat Sees Whirling Hurricane Katrina From Ocean Waves To Cloud Tops. ScienceDaily. Retrieved September 22, 2014 from www.sciencedaily.com/releases/2005/08/050830071214.htm
European Space Agency. "Envisat Sees Whirling Hurricane Katrina From Ocean Waves To Cloud Tops." ScienceDaily. www.sciencedaily.com/releases/2005/08/050830071214.htm (accessed September 22, 2014).

Share This

More Earth & Climate News

Monday, September 22, 2014

Featured Research

from universities, journals, and other organizations

Featured Videos

from AP, Reuters, AFP, and other news services

Will Climate Rallies Spur Change?

Will Climate Rallies Spur Change?

Newsy (Sep. 21, 2014) Organizers of the People's Climate March and other rallies taking place in 166 countries hope to move U.N. officials to action ahead of their summit. Video provided by Newsy
Powered by NewsLook.com
UN's Ban: Climate Change 'defining Issue of Our Time'

UN's Ban: Climate Change 'defining Issue of Our Time'

Reuters - US Online Video (Sep. 21, 2014) United Nations Secretary-General Ban Ki-moon marches with hundreds of thousands of people in New York for the international day of action on climate change. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
Thousands March in NYC Over Climate Change

Thousands March in NYC Over Climate Change

AP (Sep. 21, 2014) Accompanied by drumbeats, wearing costumes and carrying signs, thousands of demonstrators filled the streets of Manhattan and other cities around the world on Sunday to urge policy makers to take action on climate change. (Sept. 21) Video provided by AP
Powered by NewsLook.com
Climate Change Rally Held in India Ahead of UN Summit

Climate Change Rally Held in India Ahead of UN Summit

AFP (Sep. 20, 2014) Some 125 world leaders are expected to commit to action on climate change at a UN summit Tuesday called to inject momentum in struggling efforts to tackle global warming. Duration: 00:41 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.


Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News


Free Subscriptions

Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile

Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?

Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins