ملف:Thunderstorms over Estonia on a Copernicus Sentinel-1 synthetic aperture radar image.jpg

English: Synthetic Aperture Radar (SAR) is said to be weather independent. It is true in a majority of the cases - the microwaves do not interact with condensed water of clouds and light rain and the image represents the underlying land or sea. But sometimes in case of heavy rain or hail, like during the thunderstorms the size and density of water particles is enough to interact with the microwaves of a SAR. The image presents Estonia around the lakes of Võrtsjärv and Peipsi in the evening of August 12th, 2015 at 18:56 local time. During that time heavy thunderstorms were passing over Estonia, bringing car damaging apple sized hail particles with them. According to Estonian Weather Service ground-based meteorological radar the vertical profiles of the thunderstorm centres were exceeding 10 km of height.

Notice the white and purple areas in the photo over land and lake Peipsi at left. Notice also the dark areas over land. The bright-white and purple areas correspond to backscattering from the atmosphere in the heavy rainfall areas. Dark areas is land backscattering, which is attenuated, because the SAR signal travelled through the rainfall cloud. Due to the side-looking geometry of the SAR system and tall profile of the thunderstorm clouds the bright backscattering and dark attenuation areas of the same cloud are misplaced. The bright backscattering is located in the left of the dark attenuation area as satellite beam was looking from left side. Using ground based weather radar and spaceborne SAR data it is possible to re-construct the thunderstorm clouds in 3D.

Satellite look direction left (ascending orbit), incidence angle range 34-45 degrees, false colour RGB, R=VV-, G=VH- and B=VV+VH-polarisation backscatter.