Vis/NIR image close-up	AIRS infrared window channel	HSB microwave channel

Packing gusts of 296.1 kilometers per hour (184 miles per hour) and sustained winds of 241.4 kilometers per hour (150 miles per hour), Supertyphoon Pongsona struck the U.S. Island of Guam on Sunday, December 8. The storm cut off electricity over the entire island along with telephone and water service, and President George W. Bush declared the U.S. territory a federal disaster area. Pongsona is the third typhoon to hit Guam since June, and the second cyclone of supertyphoon status to hit in five years.

These images were made from data acquired by the Atmospheric Infrared Sounding System (AIRS) instrument suite aboard NASA's Aqua spacecraft just as the eye of the storm was about to pass over Guam.

This image was made using visible/near-infrared data using the AIRS instrument. Its 2-kilometer (1.24-mile) resolution shows fine details of the cloud structure and can be used to help interpret the other images. It confirms that the eye was not cloud free at the time the data was acquired, and pinpoints towering thunderheads rising up in several areas of the spiral arms (see figure 1 for close-up).

The image in figure 2 shows how the typhoon looks through an AIRS infrared "window" channel, which measures the temperature of the nearest impenetrable surface. Where the sky is clear, this window channel shows the surface of the Earth, otherwise it will show cloud tops. High cold clouds appear blue, while lower warmer clouds are green through orange. The Earth's surface, where it can be seen between the clouds, is warmest and appears red. Although the storm has a clearly defined eye, it is not cloud free and therefore shows up as yellow in this infrared image.

The image in figure 3 shows how the typhoon looks through a microwave channel of the Humidity Sounder for Brazil (HSB), a component of the AIRS instrument suite. This channel, which is sensitive to humidity, clouds and rain, sees through much of the clouds and reveals some of the inner structure of the storm. Here the eye is more clearly defined than in the infrared image and appears to be very large - perhaps 80.5 kilometers (50 miles) across. Rain areas appear as blue patches, and a very intense rain cell can be seen right over Guam itself. This cell is in the leading eye wall and is probably associated with the highest wind speeds. It is likely that much of the damage in Guam was caused by this particular part of the storm.

In the near future, when estimates of the three-dimensional distribution of the temperature, humidity and clouds in the atmosphere are also routinely derived from the AIRS sounding system, it will be possible to get a unique view of the interior of destructive storms like Pongsona. The new knowledge gained will eventually make for more accurate forecasts of such events.

The Atmospheric Infrared Sounder Experiment, with its visible, infrared, and microwave detectors, provides a three-dimensional look at Earth's weather. Working in tandem, the three instruments can make simultaneous observations all the way down to the Earth's surface, even in the presence of heavy clouds. With more than 2,000 channels sensing different regions of the atmosphere, the system creates a global, 3-D map of atmospheric temperature and humidity and provides information on clouds, greenhouse gases, and many other atmospheric phenomena. The AIRS Infrared Sounder Experiment flies onboard NASA's Aqua spacecraft and is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., under contract to NASA. JPL is a division of the California Institute of Technology in Pasadena