Monthly Archives: August 2011

On 22th August 2011, the tropical storm Irene was classified as stage 1 Hurricane while it was passing over Puerto Rico Island. With time, it gained power, reaching stage 2 on 23th in the morning and stage 3 as it was approaching the coast of the Bahamas, before heading north aside the US East Coast (about 400km off the shore). Its intensity then diminished down to stage 1 when it passed Cap Hatteras. Still, the forecast trajectory announced it would reach New York City which, unlike the Caribbean’s, is not very used to this type of natural events (Gloria, the last hurricane that hit the city, dates back to 1985).

As soon as the news came out, ASAR (Advanced Synthetic Aperture Radar onboard ENVISAT) acquisition plans were updated by ESA (the European Space Agency) to get a radar snapshot of the hurricane. Roughness products show the two radar images, acquired over Cap Hatteras before the cyclone reached the American East Coast. The eye of the hurricane is well depicted on the first image (dark disk). The displacement of the hurricane is shown by the new location of the eye, passing over the Sound of Pamlico 12 hours later.

Radar observation presents many advantages: the capacity to see through rain and clouds, at night and days and with a high resolution to assess geophysical parameters such as surface wind, swell and currents. Besides, its wide swath of 400km gives a synoptic view of such meso-scale phenomenon. Continue reading →