IR Satellite, Lightning & Radar
What does the brightness of a cloud mean on the Infrared Satellite Imagery?
All objects emit electromagnetic radiation, which is measured by infrared ('IR') radiometers on weather satellites. For easy interpretation, the energy measured by the infrared satellite instruments is converted to a temperature. We use infrared satellite imagery in order to see the cloud patterns both during the day and night - imagery in the visible spectrum would only show cloud tops which relflect sunlight, and therefore is dark at nighttime. Usually, in IR imagery, cold cloud tops are white and hot surfaces appear black. In some instances, the colour of the colder temperatures is enhanced with various colours, to highlight the highest and deepest clouds. Animated time sequences of infrared images are shown on our website, and the Bermuda Weather Channel. Overlaid on top of these images, when available, are Doppler radar images. For further information on Doppler imagery, please see our information page here.
How are the lightning strikes detected?
Lightning is an electrical discharge in the atmosphere, which not only produces light and sound (thunder), but also radio waves, known in meteorology as 'sferics'. These radio waves can be detected and triangulated by a global network of specially tuned sensors. The trangulated position of a lightning discharge is displayed as a cross on the imagery which we display and use at the Bermuda Weather Service. The colour of the cross indicates how recently the sferic was detected.