THE AVAILABLE ENERGY OVER A SCOTS PINE PLANTATION - WHATS UP FOR PARTITIONING

Errors influencing the calculation of the available energy above a for est are discussed. The main emphasis is put on the investigation of th e problems affecting the measurement of net radiation. This is done by utilizing the data set of a surface energy balance experiment which w as conducted in and above a Scots Pine plantation from May 11 to 22, 1 992. During that Hartheimer Experiment (HartX) there were redundant me asurements of net radiation using five different radiometers of three different designs. The initially fair agreement between the net radiom eter readings was considerably improved by introducing different respo nsivities for the short- and longwave range. The mean deviations to th e relative net radiation after correction vary between - 1.4 and 1.2 W m(-2) with standard deviations between +/- 5.4 and 6.6 Wm(-2). The tot al error referring to the available energy is estimated to be up to +/ - 36 Wm(-2) (+/- 6%) around midday decreasing to 10 Wm(-2) during nigh ttime.