The planetary boundary layer (PBL) typically extends from Earth’s surface to several hundreds to a few thousands of meters above ground level. In the PBL, measurements of temperature, relative humidity, horizontal wind velocity and direction, and upward wind velocity usually exhibit rapid fluctuations. In essence, the PBL “connects” the mid- to upper-atmosphere with the ground surface. Scientists study the PBL to better understand how conditions at the surface influence behavior of the entire atmosphere and weather and climate across the globe.
For many years, ATDD scientists have performed PBL measurements in various environments and landscapes, including the desert Southwest and pastureland in the Southern U. S. Recently, ATDD has undertaken a measurement program at the Chestnut Ridge Environmental Study site on the U. S. Department of Energy reservation near Oak Ridge National Laboratory. The 60 m tall tower at Chestnut Ridge extends 20 m above the dense deciduous oak-hickory forest at the site, which is typical of the Southeastern U. S. The tower has been intensively instrumented (at 12 heights from 5m to 60m) with 3-dimensional sonic anemometers (fast-response wind measurement devices) and precision temperature sensors. Observations gathered from the tower include mean, turbulent, and cross-correlations of both wind and temperature. The tower is also available for other short- or long-term collaborative studies.