home site map home clouds climate wx modeling learn home csu nsf home learn science research kt news directory webmaster



The surface energy budget

The Planetary Boundary Layer

The PBL is characterized by turbulence because of the friction between the atmosphere and the earth's surface. The PBL height depends on the stability of the atmosphere - which can be determined from above and below. When there are high winds in the free atmosphere, the turbulence near the surface is increased and the PBL gets thicker.

The stability is also determined at the bottom of the PBL by the surface temperature. On warm days, thermals rising from the surface increase the depth of the PBL. The PBL is usually at its shallowest point during the night. The height is usually about 1 km (about 0.62 miles) above the surface, but it can range from 30 m (about 100 ft.) to 3 km (almost 2 miles).

If you want to learn more about the PBL and its role in air quality, try visiting this site.

This Windows to the Universe website can tell you how the planetary boundary layer and surface affect weather and climate.

Back to climate topics

Links and resources