Wind fronts in the Strait of Messina (Italy)

The figure shows an ERS-1 SAR image (100Km x 100Km) of the Mediterranean sea north of the Strait of Messina (I) acquired on the 8th of September 1992 at 21:13 UT (orbit 6014, frame 765).
It shows north-west of Gioia sea surface manifestations of katabatic wind tongue (bright blob in the image). Furthermore, between the island of Stromboli and the Sicilian coast, a granular pattern can be delineated which we believe are sea surface imprints of atmospheric convective cells. This cellular structure is destroyed in the vicinity of the Sicilian coasts by the katabatic wind blowing from the mountains onto the sea.

Katabatic winds are cold winds blowing in the evening and night down a sloping terrain (gravity flow) and, at a coast, over the adjacent sea surface. These winds are generated because in the evening and night the air near the surface cools off faster over the land than over the sea.
Over mountain slopes, a horizontal density difference develops between the cooled air at the slope surface and the free air in the same altitude over the lower ground or the sea.
This results in a down-hill flow of cold air.

Sea surface manifestation of katabatic wind field have often been identified in the summer on ERS-1 SAR images of coastal regions which are adjacent to mountainous areas.
In the lower part of the image an oceanic internal wave train propagating southward in the Strait of Messina can be delineated.

(From Measurements of mesoscale oceanic and atmosphere phenomena by ERS-1 SAR - Werner Alpers).

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry