Satellitenaufnahme des Pazik vom
30 June 2010
Viewed from space, the most striking feature of our
planet is the water. In both liquid and frozen form, it covers
75% of the Earth’s surface. It fills the sky with clouds. Water
is practically everywhere on Earth, from inside the rocky crust
to inside our cells.
This detailed, photo-like view of Earth is
based largely on observations from the Moderate Resolution Imaging
Spectroradiometer (MODIS) on NASA’s Terra satellite. It is one of
many images of our watery world featured in a new story examining
water in all of its forms and functions. Here is an excerpt: “In
all, the Earth’s water content is about 1.39 billion cubic
kilometers (331 million cubic miles), with the bulk of it, about
96.5%, being in the global oceans. As for the rest, approximately
1.7% is stored in the polar icecaps, glaciers, and permanent snow,
and another 1.7% is stored in groundwater, lakes, rivers, streams,
and soil. Only a thousandth of 1% of the water on Earth exists as
water vapor in the atmosphere. Despite its small amount, this water
vapor has a huge influence on the planet. Water vapor is a powerful
greenhouse gas, and it is a major driver of the Earth’s weather and
climate as it travels around the globe, transporting heat with it.
For human needs, the amount of freshwater for drinking and
agriculture is particularly important. Freshwater exists in
lakes, rivers, groundwater, and frozen as snow and ice.
Estimates of groundwater are particularly difficult to make, and
they vary widely. Groundwater may constitute anywhere from
approximately 22 to 30% of fresh water, with ice accounting for
most of the remaining 78 to 70%.”