THE ASA SHUTTLE - A SYSTEM FOR MOBILE SAMPLING OF AIR-TEMPERATURE ANDRADIATION

The Asa shuttle-a system for mobile sampling of air temperature, solar -, and net radiation in a shelterwood experiment was developed. The sh uttle was equipped with thermocouples which measured at 6 different he ights. Tree radiometers measured total solar, photosynthetically activ e-, and net radiation. The shuttle, which was driven by an electric mo tor, moved back and forth along a 780 m long track with a speed of abo ut 2 m s-1. After each ''trip'' data were transferred to and stored in a personal computer. After recharging the batteries the shuttle was r eady to start a new trip about every 20 min. Two stationary measuremen t modules placed close to the track were used to test the measurement accuracy of the shuttle. The Asa shuttle made it possible to measure a ir temperatures and radiation with high spatial resolution, accuracy a nd repeatability and with high reliability over long time periods. In the present study the shuttle was primarily used in frost studies, but it can also be used in any study where detailed knowledge of meteorol ogical processes in the forest are needed.