The troposphere is the lowest layer of Earth's atmosphere. We
live in the troposphere. Weather happens in this layer. Most
clouds are found in the troposphere. The next layer up is the
stratosphere. Click on image for full size Original artwork by
Windows to the Universe staff (Randy Russell). The troposphere
is the lowest layer of Earth's atmosphere. The troposphere
starts at ground level. The top of the troposphere is about 11
km up (that's 7 miles or 36,000 feet). The layer above the
troposphere is called the stratosphere. Most of the air (about
3/4ths) in our atmosphere is in the troposphere. Almost all
weather happens in the troposphere. Most clouds are found in
this lowest layer, too. The jet stream is near the top of the
troposphere. This "river of air" zooms along at 400 km/hr (250
mph)! The troposphere is warmest near the ground. Sunlight heats
the ground (or oceans!). The ground heats the air that is
closest to it... at the bottom of the troposphere. The higher up
you go in the troposphere, the cold