Calibration of tipping‐bucket flow meters and rain gauges to measure gross rainfall, throughfall, and stemflow applied to data from a Japanese temperate coniferous forest and a Cambodian tropical deciduous forest

Tipping‐bucket flow meter and rain gauge (TBFM/TBRG) are widely used for the measurement of gross rainfall ( GR ), throughfall ( TF ), and stemflow ( SF ) to evaluate the amount of interception loss ( I ). However, TBFM/TBRG cannot measure the inflow rate during tipping and underestimates the inflow rate. To correct this systematic bias, 33 total calibrations were conducted for five types of TBFM/TBRG in the laboratory. The tipping time increased with the bucket volume, and the underestimation during one tip was higher for TBFM/TBRG of larger capacity. With the use of the scaled actual inflow rate and the actual volume of a single tip from the measured static volume of a single tip when the inflow rate is zero, the common calibration curves were obtained as quadratic equations for each of the five types within an error range of ±3%. We measured GR and TF by using TBRG and TBFM with a resolution of 0.2 mm and measured SF by TBRG with a single‐tip static volume of 15.7 cm 3 in a Japanese temperate coniferous forest (TCF) and a Cambodian tropical deciduous forest (TDF). At both sites, the calibration curves needed to be applied to obtain GR , TF , and SF on an event scale with an underestimation degree of less than 3%. Without applying any calibrations, the higher rainfall intensities in TDF caused larger underestimations of GR , TF , and SF and larger overestimations of I compared with results for TCF. On an annual scale, the degree of overestimation of I relative to GR (Δ I / GR ) was 1.2% in TCF and 3.5% in TDF, and Δ I / I was at least 10% at both sites. Copyright © 2012 John Wiley & Sons, Ltd.