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Seen from Space 2003

Snow Ice in the Northern Hemisphere (April 2003)

 

Image (A) is a cloud-free image composed of GLI data acquired from April 7 to May 7. The image was taken from right above the Arctic pole, and Japan can be seen in the upper right of the image (but upside down). Snow areas, such as sea ice that covers the Arctic Ocean and snow in the permafrost and in the northern coniferous forest in Siberia (right of the Arctic Ocean), Alaska and Canada (left of the Arctic Ocean), were colored light blue.

In image (B), snow and sea ice were distinguished by color. White indicates snow on the ground; light blue, sea ice; dark green, ground; and dark blue, ocean. Snow and sea ice reflect the sunlight so much that it is interrelated with the amount of radiant heat that the land surface receives. Therefore, snow and sea ice distribution is important data related to the Earth's climate.

Reflection intensity of snow differs with the extent of snow impurities. If snow is impure and seems blackish, it does not reflect the sunlight so much and absorbs the heat, so the snow temperature rises. Snow impurities, as seen in image (C), are caused by dust and dirt in the air that lie thick on the ground with snow. If snow is impure, it speeds up the melting of snow ice in the spring, and that changes the rhythm of the turning of the seasons. Snow grain size, as image (D) represents, is small in new snow and gradually becomes bigger. Grains tend to be borne sooner when the snow temperature is high, and that is closely interrelated with snow impurities.

In image (C), snow impurities are low in Greenland (dark blue area in the bottom left of the image). Because Greenland is situated in highlands over 3,000m and has no major city around it, it is less affected by air pollution than sea ice areas, and snow impurities are low. In image (D), snow grain size is bigger at lower latitudes in the snow area, and it changes with the rising of the temperature to the south. (The black circle at the North Pole was not observed by GLI).

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