Correction of Canopy Interception Loss Measurements in Temperate Forests: A Comparison of Necessary Adjustments among Three Different Rain Gauges Based on a Dynamic Calibration Procedure

Abstract

ABSTRACT Tipping-bucket rain gauges are used widely to measure the amount and intensity of gross rainfall and throughfall in forests, despite the fact that their systematic underestimations are well known. To the knowledge of the authors, no dynamic calibrations for the budget-conscious Davis gauge (Rain Collector II, Davis Instruments, California) have been published. Thus, five Davis gauges were dynamically calibrated under different constant intensities of inflow and a correction equation was derived. The derived correction equation for the Davis rain gauge is V = −0.2005Q2 + 0.702Q + 1 (R2 = 0.95, p < 0.001), where V is the actual volume of a single tip scaled by the static volume of single tip c (cm3 cm−3), and Q is actual inflow scaled by c (s−1). The Davis rain gauge was then compared to the Onset rain gauge and the Ota rain gauge, and the corrections were applied to field observation data of canopy interception loss from a temperate forest in Japan. It is necessary to apply corrections to gross rainfall and throughfall data by tipping-bucket gauges because the results reveal that such corrections change the actual interception loss computed by values from −20% to 40%, depending on the combination of gauges employed. This difference is not trivial. The systematic bias of the Davis gauge is larger than the Onset and Ota gauges. Thus, it is recommended that researchers using Davis rain gauges apply the dynamically calibrated correction equation presented here to ensure more reliable estimates of gross rainfall and canopy interception loss.