Shop Windows to the Universe

Ready, Set, SCIENCE!, by the National Research Council, focuses on K-8 science classsrooms. Check out the other publications in our online store, as well as classroom materials.
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

The troposphere is the lowest layer of Earth's atmosphere. The troposphere starts at Earth's surface and goes up to a height of 7 to 20 km (4 to 12 miles, or 23,000 to 65,000 feet) above sea level. Most of the mass (about 75-80%) of the atmosphere is in the troposphere. Almost all weather occurs within this layer. Air is warmest at the bottom of the troposphere near ground level. Higher up it gets colder. Air pressure and the density of the air are also less at high altitudes. The layer above the troposphere is called the stratosphere.

Nearly all of the water vapor and dust particles in the atmosphere are in the troposphere. That is why most clouds are found in this lowest layer, too. The bottom of the troposphere, right next to the surface of Earth, is called the "boundary layer". In places where Earth's surface is "bumpy" (mountains, forests) winds in the boundary layer are all jumbled up. In smooth places (over water or ice) the winds are smoother. The winds above the boundary layer aren't affected by the surface much.

The troposphere is heated from below. Sunlight warms the ground or ocean, which in turn radiates the heat into the air right above it. This warm air tends to rise. That keeps the air in the troposphere "stirred up". The top of the troposphere is quite cold. The temperature there is around -55° C (-64° F)! Air also gets 'thinner' as you go higher up. That's why mountain climbers sometimes need bottled oxygen to breathe.

The boundary between the top of the troposphere and the stratosphere (the layer above it) is called the tropopause. The height of the tropopause depends on latitude, season, and whether it is day or night. Near the equator, the tropopause is about 20 km (12 miles or 65,000 feet) above sea level. In winter near the poles the tropopause is much lower. It is about 7 km (4 miles or 23,000 feet) high. The jet stream is just below the tropopause. This "river of air" zooms along at 400 km/hr (250 mph)!

Last modified January 11, 2010 by Randy Russell.

Shop Windows to the Universe Science Store!

The Fall 2009 issue of The Earth Scientist, which includes articles on student research into building design for earthquakes and a classroom lab on the composition of the Earth’s ancient atmosphere, is available in our online store.

Windows to the Universe Community

News

Opportunities

You might also be interested in:

Traveling Nitrogen Classroom Activity Kit

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

Aerosols: Tiny Particulates in the Air

When you look up at the sky, you are looking at more than just air. There are also billions of tiny bits of solid and liquid floating in the atmosphere. Those tiny floating particles are called aerosols...more

Atmospheric Boundary Layer

The lowest part of the troposphere, closest to Earth's surface, is called the "boundary layer" (or planetary boundary layer or atmospheric boundary layer). Near the surface, the texture of the...more

Wind

Wind is moving air. Warm air rises, and cool air comes in to take its place. This movement creates different pressures in the atmosphere which creates the winds around the globe. Since the Earth spins,...more

Atmospheric Chemistry of Earth's Troposphere

When you think of chemistry, do you think about mixing colored liquids in test tubes and maybe making an explosion... or at least a nice puff of smoke? Did you know that a lot of chemistry happens in Earth's...more

Jupiter's Troposphere

The troposphere of Jupiter is where the clouds are. Clouds form in regions of strong atmospheric motion, when condensation takes place. The troposphere is the region rapidly stirred by vertical motions....more

Uranus' Tropospheric Temperature Profile

This is the temperature profile of Uranus' troposphere. The temperature becomes cooler with height until the tropopause, or "top" of the troposphere is reached. The tropopause is defined to be the altitude...more

Clouds with Vertical Growth

Clouds with vertical growth include cumulus and cumulonimbus clouds. These clouds grow high up into the atmosphere rather than spreading across the sky. They span all levels of the troposphere and can...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA