Severe Tropical Cyclone Donna is the strongest off-season South Pacific tropical cyclone on record during the month of May and it has been upgraded to a category five storm, the most destructive wind-speed level.
The cyclone is in north of archipelago Vanuatu located in the South Pacific Ocean.
On May 4th the Sea and Land Surface Temperature Radiometer, carried by Sentinel-3A satellite, captured the cyclone on the cloud-tops.
Thanks to the infrared bands SLSTR shows us the round-shaped temperature profile all over the storm: the temperature decreases as we go into the eye of the cyclone, where the clouds, that are at -86 degrees Celsius, are at the limit of the troposphere.
The SAR sensor of Copernicus Sentinel 1 radar waves can penetrate all weather conditions including clouds and rain.
The size, the shape and the wind fields can be used to derive wind intensity and direction for even extreme weather events.
A SAR image is a measure of the amount of energy reflected back to the radar antenna following interaction of the transmitted pulse with the ocean’s surface. The degree of backscatter depends on the roughness of the surface at the scale of the radar wavelength.
For the ocean surface, the short scale roughness is influenced primarily by the surface wind speed.
The image, captured on 4 may 2017, shows an imprint of the cyclone Donna on the ocean surface roughness.
The eye of the cyclone appears darker than its surrounding area because the wind speed at the center of the cyclone is lower.
On the right side of the image there is Tikopia island with its internal lake (visible as the white pixels with black pixels inside).
Tikopia is one of the Solomon Islands of Melanesia.
On the right a zoom of Tikopia island acquired by the spatial and temporal resolution Copernicus Sentinel-2 satellite.