FOOTPRINTS OF STORMS ON THE SEA IN THE JERS-1 SAR IMAGE

SEASAT synthetic aperture radar (SAR) echoes from the sea show beautif ul images of storms over the ocean. However, the mechanisms by which s uch storm images are created have not yet been revealed very well. The core of these images is usually an echo-free hole which is attributed to the damping of the radar-detectable short gravity waves by the int ense rain in the storm core. The bright area surrounding the core is b elieved to be caused by strong winds diverging from the downdraft whic h is collocated with the intense rain. The outer boundary of the brigh t area has been found to be associated with the classical gust front. During the Tropical Ocean Global Atmosphere/Coupled Ocean-Atmosphere R esponse Experiment (TOGA/COARE), continuous observations of rain by sh ipborne radars were carried out. One image of JERS-1 SAR taken in this period contains storms that were within the observation area of a shi pborne radar. The SAR image and the rain-radar image are compared. Eve n though the signal-to-noise ratio of the SAR image is very low, there is good correspondence between heavy rain areas and some of the dark areas in the SAR image. The boundary of a rain-induced dark area is fo und to correspond approximately to the radar reflectivity factor (Z-fa ctor) of 35 dBZ or 5.5 mm/h of rain.