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Mexico Mexico

Latitude: 15° 30' N - Longitude: 94° 00' W

Visible on this ERS-2 SAR image is a bright area near the coast which results from wind which is blowing from the mountains in the Isthmus of Tehuantepec (Mexico) onto the eastern tropical Pacific Ocean. Also visible are sea surface manifestations of several oceanic internal wave packets. Note that in the area with a higher wind speed the internal waves have a lower image contrast. This is a consequence of the fact that the hydrodynamic modulation of the short surface waves ("Bragg waves") by a variable current decreases with wind speed.
Sakishima-gunto Sakishima-gunto

Latitude: 23° 49' N - Longitude: 122° 42' E

Atmospheric front near Taiwan. The dark and bright bands on the SAR image extending from NE to SW result from an atmopsheric front that moves in a southeastward direction. The surface analysis map of the Japan Meteorological Agency of December 14, 1994 at 12 UTC shows an occlusion front located approximately at the position of the bands in the SAR image The bright band is very likely caused by a squall line ahead of the front,while the dark band and the dark patches are caused by rain impinging onto the sea surface where they generate turbulence in the uppermost water layer and thus damp the C band Bragg waves. Behind the front the image intensity is almost uniform indicating a uniform wind field. The wind direction in this backward side of the front can be obtained from the direction of the faintly visible streaks,which are oriented almost normal to the dark band and which are sea surface imprints of atmospheric boundary layer rolls.
Sulu Sea Sulu Sea

Latitude: 8° 21' N - Longitude: 118° 32' E

The bright area in the right-hand section of this image is caused by winds (downdrafts) associated with tropical rain cells. Sea surface manifestations of oceanic internal waves are also visible on this image.
Surinam Surinam

Latitude: 6° 08' N - Longitude: 53° 42' W

This ERS-1 SAR image shows an atmospheric front in the tropical Atlantic with several small tropical rain cells embedded (the irregular patches with dark areas).
Makassar Strait Makassar Strait

Latitude: 1° 56' S - Longitude: 117° 43' E

In the upper part of this image an atmospheric front with several associated rain cells can be delineated . In the lower part the gust front of a large cluster of rain cells is visible.
# Orbit Frame(s) Satellite Date Time Location
1 03444 3285-3303 ERS-2 17-Dec-1995 16:44 Mexico
2 17859 0459-0477 ERS-1 14-Dec-1994 14:15 Sakishima-gunto
3 24091 3429-3447 ERS-2 29-Nov-1999 02:29 Sulu Sea
4 04220 3483 ERS-1 06-May-1992 13:31 Surinam
5 10521 3609-3627-3645-
3663-3681
ERS-2 25-Apr-1997 02:27 Makassar Strait

If you have any comments on these images please write an e-mail to alpers@ifm.uni-hamburg.de.

Introduction

Atmospheric fronts are boundaries of air masses with different properties. Often atmospheric fronts separate air masses of different temperatures. Usually the wind speed and wind direction are different at both sides of an atmospheric front. Over the ocean this results in a differing short-scale sea surface roughness and thus on the SAR image atmospheric fronts appear as boundaries between areas of different image intensity, which easily can be delineated on SAR images of the sea surface.