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A Wintry Tale of Two Seasons: Earth Images of the Week September 14, 2012
Astronaut photo of Guam
The snow in the image from Siberia is fresh, while that in Tasmania appears to have been around long enough to melt in some of lower-elevation fringes.
The ratio of day and night is changing around the world at nearly the fastest pace of the year as the sun rapidly approaches the September equinox.

This will mark the beginning of spring south of the equator and the onset of autumn to the north.

The resulting shifts in weather patterns are now producing some of the earliest snowfall of the season in far northern latitudes, while late-winter snowfall lingers in a few southern climes.

The images to the right illustrate that trend in progress on the closing day of August and the fourth day of September 2012.

The top image was captured on August 31 when NASA’s Terra satellite passed over the Australian island state of Tasmania.

It shows a blanket of late-winter snow over the Central Highlands, where the tallest peaks rise to about 5,600 feet in elevation.

The snow-covered alpine terrain is in contrast to the various shades of green that surround the mountains. The darkest greens represent the heavily wooded temperate rain forests at lower elevations, while the lighter greens in the far right are grasslands and farms.

The bottom image of north-central Siberia was snapped by NASA’s Terra satellite on September 4. The bright snow-capped highlands of the Putorana Plateau shows up dramatically against the surrounding brown landscape, which is of volcanic origin. A few dark blue lakes and rivers can also be seen.

While the snow in the two images looks somewhat similar, to a trained specialist like NASA scientist James Foster, subtle differences are apparent.

“Because the snow in Siberia is likely fresh and probably fell at night, the snow-line is nearly the same elevation throughout the scene,” Foster noted. “There’s no melting on southern and western slopes ... and there is no snow below a certain elevation. This is not the case in the Tasmania image, where (a portion of) the snow pack has had an opportunity to melt.”

Full story and image: NASA