ORIGIN OF STORM FOOTPRINTS ON THE SEA SEEN BY SYNTHETIC-APERTURE RADAR

Spaceborne synthetic aperture radar can detect storm footprints on the sea. Coastal weather radar from Cape Hatteras provides evidence that the echo-free hole at the footprint core is the result of wave damping by rain. The increased radar cross section of the sea surrounding the echo-free hole results from the divergence of the precipitation-forced downdraft impacting the sea. The footprint boundary is the gust front; its orientation is aligned with the direction of the winds aloft, which are transported down with the downdraft, and its length implies downdraft impact 1 hour earlier at a quasi-stationary impact spot. The steady, localized nature of the storm remains a mystery.