Should We
Talk About the Weather?
   
It’s early summer 1994, 12:34 p.m. local time, and the Canadian Twin Otter research aircraft is flying 20 meters (about 65 feet) above the boreal forest canopy near Prince Albert, Saskatchewan. Scientists are busy measuring the exchanges of gas and heat between the forest and the lower atmosphere when the plane flies into an unseen vortex of intense, heat-induced winds—a "dust devil," as these phenomena are called in desert regions of the southwestern United States. Instruments aboard the aircraft clock the wind shift across the wall of the vortex at nearly 20 meters per second (45 miles per hour) and the updraft at the center of the vortex at 11 meters per second (25 miles per hour). Without warning, the strong winds catapult the Twin Otter upward and sideways in a few seconds. Fortunately, the pilot is able to stabilize the aircraft and return the plane and crewmembers safely to the ground, albeit a little shaken up. That summer the Twin Otter flew into eight such vortices in four months (MacPherson and Betts, 1997).
 
  by David Herring
Page 2

Boreal Ecosystem Series
· Introduction to BOREAS
· The Mystery of the Missing Carbon
· Should We Talk About the Weather?
· Evolving in the Presence of Fire
· The Migrating Boreal Forest

The boreal forestAs an integral part of NASA’s Boreal Ecosystem-Atmosphere Study (BOREAS) measurement strategy, a team of researchers, including Alan K. Betts from Vermont, used instruments aboard the Twin Otter and on forest towers to measure interactions between the forest and the lower atmosphere. During each season from 1994—97, data were collected on the exchanges of heat, momentum, carbon dioxide, ozone and water vapor to gain insights into the ongoing "dialogue" that occurs between the boreal ecosystem and the atmosphere. Their goal is to understand how changes in air temperature, moisture and carbon dioxide levels may impact the boreal ecosystem and what role the boreal forest plays in global-scale climate changes.

One of Betts’ primary research objectives was to quantify the amount of heat emitted and light reflected by the boreal forest. The vortices of hot air that occasionally sent his colleagues on the Twin Otter "thrill rides" reinforced what other measurements were showing—the boreal forest stores and releases significantly more heat to the atmosphere in the spring and early summer than scientists previously thought.

next Everyone Complains About the Weather

The data used in this study are available in one or more of NASA's Earth Science Data Centers.

The boreal forest canopy as seen from the top of a tower about 30 meters above the ground. To measure the fluxes of heat and gases exchanged between the forest ecosystem and the lower atmosphere, the BOREAS team mounted sensitive instruments on these towers at multiple sites in the Canadian boreal forest. Measurements from these flux towers were complimented by measurements made aboard the Twin Otter research aircraft flying at roughly this altitude. (Photograph courtesy BOREAS project)