ASAR image of Frances passing near Puerto Rico

This ASAR Global Monitoring Mode image acquired 1 September 2004 shows Hurricane Frances passing near the island of Puerto Rico. ASAR returns details of surface roughness from which wind and wave fields at the base of the hurricane can be derived. Although the resolution of this image is approximately 1 km, the eye is clear - because of tranquil weather prevailing within it, the water within it is smoother than that around it - plus the surrounding spiral structure of the eye wall, where the winds are fastest and sea roughest.