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March 20 marked the beginnin gof astronomical spring
 in the Northern Hemisphere.

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Called the vernal equinox, or spring equinox, this event

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reulsts in nearly equal daylight and darkness across the planet.

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NOAA's GOES-16 and 17 satellies constantly observe the 
same region of Earth,

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allowing a view of the terminator as it moves 
across the Western Hemisphere.

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The terminator is the edge between the shadows of nightfall and the sunlight of dusk and dawn.

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The shape of the terminator curve changes with the seasons.

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On the vernal equinox each year, the terminator is a stragiht north-south line over the equator.

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The seasons change due to the tilt of Earth's axis as it orbits the sun.

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The titlt means the two hemispheres are exposed to different sun angles and variable lengths of daylight during the year.

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Throught the year, NOAA satellites observe the markers of seasonal change.

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Earth from Orbit: Vernal Equinox

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NASA Meatball

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