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Winds - Measuring ocean winds from space
Synoptic View of Ocean Surface Winds Measured by NSCAT, September 21, 1996
Synoptic View of Ocean Surface Winds

This image shows ocean surface wind speeds and directions over the Pacific Ocean on 21 September 1996 as they were measured by the NASA Scatterometer (NSCAT) which was onboard Japan's Advanced Earth Observing Satellite (ADEOS). The background color indicates wind speed and the white arrows show the direction of the wind. The basin-wide wind field is representative of near-Equinox atmospheric circulation. The strong Trade Winds (red) blow steadily from the cooler subtropical ocean to the warm water of the Intertropical Convergence Zone (ITCZ) located just north the Equator. Instead of blowing in the north-south direction, the winds are deflected westward by the Corriolis Force due to the Earth's rotation. The air rises over the warm water of ITCZ and sinks in the subtropics at the Horse Latitudes, forming the Hadley Circulation. Both the convergence area at the ITCZ and the divergence area at the Horse Latitudes are indicated by low wind speed of blue color. In the mid-latitudes, the high vorticity due to the Corriolis Force generates cyclones (yellow spirals) moving in the eastward direction. Two typhoons are observed in the western Pacific. Typhoon Violet is just south of Japan. After these data were taken, Typhoon Violet struck the East Coast of Japan causing damage and deaths. Typhoon Tom is located further east and did not land.

The image is based on preliminary processing of the first set of NSCAT observations, using prelaunch model function and calibration. Improvement is expected after the standard calibration and beam balancing procedures. The image is produced by objective interpolation as described by Tang and Liu [JPL Publication 96-19, 1996] based entirely on NSCAT data. This preliminary analysis clearly demonstrates that the high spatial resolution of NSCAT data improves the monitoring of sever storms, such as typhoons, which are usually grossed over by conventional methods. It also shows that the repeated global coverage provides a better description of atmospheric circulation over ocean that is not adequately sampled in the past.

Credit: NASA/JPL


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