Summer solstice in SEVIRI imagery

Summer solstice in SEVIRI imagery

21 June 2014 06:00 UTC

Summer solstice in SEVIRI imagery
Summer solstice in SEVIRI imagery

Experts from the Hungarian Meteorological Service tracked the 2014 summer solstice using Meteosat-10 imagery.

Last Updated

05 November 2020

Published on

21 June 2014

by Mária Putsay, Ildikó Szenyán and Zsófia Kocsis (Hungarian Meteorological Service)

On the 21 June at 10:51 UTC it was the summer solstice this year. From the Meteosat geostationary satellite we could clearly observe this feature.

 The Earth illuminated by the sun at the summer solstice at 06:00 UTC (Meteosat-10 Natural Colours RGB image, 21 June, 06:00 UTC)
Figure 1: The Earth illuminated by the sun at the summer solstice at 06:00 UTC (Meteosat-10 Natural Colours RGB image, 21 June, 06:00 UTC)

Figure 1 (above right) shows full disk Natural Colours RGB image at 06:00 UTC on 21 June. In the illuminated area we can clearly see the surface features and clouds. The black colour shows the area where sun had not yet risen, so it was still night. The boundary line between day and night (the so-called terminator line) and the rotation axis of the Earth has a 23.5 degree inclination on that day.

The 24-hour animation of images taken every 15 minutes, shows how the Northern Hemisphere was illuminated by the Sun over the summer solstice (21 June 12:00 UTC to 22 June 12:00 UTC).

Download animation

On Figure 2 (Meteosat-10, 21 June, 23:45 UTC) we can see that the sun never set over the North Pole on that day.

 

Figure 2: Meteosat-10 Natural Colour RGB, 21 June, 23:45 UTC

The rotational axis of the Earth is not perpendicular to the plane of the orbit. The difference between the rotational axis and the perpendicular is 23.5 degree (see Figure 3).

 

Figure 3: Rotational axis of the Earth

In half of the annual orbit the Northern Hemisphere gets more sunlight, while in the other half it's the Southern Hemisphere that gets more sunlight. At the equinox both hemispheres get the same amount of radiation. This is the reason for the seasons' progress.

The effect described above can be clearly seen on satellite images in Figure 4. In the first row we can see the images corresponding to the autumnal equinox (September 2013), in the second row to the winter solstice (December 2013), in the third row to the vernal equinox (March 2014), in the fourth to the summer solstice (June 2014) of the North Hemisphere at 06:00, 12:00, 18:00 and 24:00 UTC. In June and December we can see the midnight sun.

 

Figure 4: Meteosat-10 Natural Color RGB, seasonal equinoxes

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