Cold air drainage - mobile transect studies

<section><para>Observed temperatures on “cold air” transects at 33 locations within the HJ Andrews Forest. Data are sampled every 15 minutes with Hobo portable sensors mounted on rebar approximately 1.5 m above ground. Radiation shields are the “HJA short” type, which is made from PVC tubing, cut lengthwise and mounted above the sensor; sensors are open to the ground. Most sensors are located under dense forest canopy, with little solar radiation exposure. Many sensors also record illumination, which is useful in quantifying light exposure. The lower Lookout Creek transect (10 stations) is located just to the west of the concrete bridge, and intersects RS10. The upper Lookout Creek transect (11 stations) extends north from the north slope of Lookout Mountain, across Lookout Creek, and ends below the CENMET benchmark station. East of the upper transect, there is a short, 4-station transect across Cold Creek, a tributary of Lookout Creek. North of the upper transect, a 5-station cluster samples locations near a stream channel, above and below a spring. Single sensors are located downslope from the Roads End rain gauge near the southern border of the forest (high elevation, but locally low topographic position), and near the summit of Carpenter Mountain, on the northern border of the forest (high elevation, high topographic position, exposed to the free atmosphere). Two sensors will located temporarily in and above a sink northeast of the CENMET benchmark station. The upper and lower Lookout Creek transects were established in 2002, with others placed at later dates.</para></section>