Fog over ocean water. The low-lying fog is within the atmospheric boundary layer.
Click on image for full size
Image Courtesy of Amy Hatheway

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 ground has a strong influence on the movement of winds. Higher up, above the boundary layer, wind speed is much less affected by the details of the surface below. As you might expect, different surfaces have more or less influence on wind flow, so the thickness of this boundary layer varies. The boundary layer is quite thin over smooth water or ice, and much thicker over hilly, tree-covered, or urban terrains with many large buildings. The boundary layer typically extends upward about 200 to 500 meters (650 to 1,640 feet), but can be as thin as 50 meters (164 feet) or as deep as 2 km (6,562 feet). The depth of the boundary layer also tends to vary with latitude. Like the thickness of the troposphere as a whole, the depth of the boundary layer is usually greatest in the tropics and least near the poles.

Last modified July 27, 2009 by Randy Russell.

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

Wind

Wind is moving air. Warm air rises, and cool air comes in to take its place. This movement creates the winds around the globe. Winds move at different speeds and have different names based on their speed....more

Rainbows

Rainbows appear in the sky when there is bright sunlight and rain. Sunlight is known as visible or white light and is actually a mixture of colors. The sun's rays pass through millions of raindrops. A...more

The Four Seasons

It takes the Earth one year to travel around the sun one time. During this year, there are four seasons: summer, autumn, winter, and spring. Each season depends on the amount of sunlight reaching the...more

Research Aircraft

Scientists sometimes travel in airplanes that carry weather instruments in order to gather data about the atmosphere. These research aircraft bring air from the outside into the plane so scientists can...more

Anemometer

An anemometer is a weather instrument used to measure the wind (it can also be called a wind gauge). These instruments can be used in a backyard weather station or on a well-equipped scientific research...more

Thermometer

Thermometers measure temperature. "Thermo" means heat and "meter" means to measure. You can use a thermometer to measure the temperature of many things, including the temperature of...more

Weather Balloons

Weather balloons are used to carry weather instruments that measure temperature, pressure, humidity, and winds in the atmosphere. The information collected from the instruments on weather balloons are...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