Effect of rainfall intensity on the mechanical biases of tipping bucket rainfall measurements

Tipping bucket rain gauges are worldwide implemented due to their simplicity, low-energy consumption, and cheaper cost. Being their main disadvantage measurement biases caused by different factors such as wind, mechanical, etc. This work focus on errors caused by rainfall intensity variation, and its effect into the measurement mechanism, which results in rainfall underestimation, specially at extreme events. Aiming to understand these biases and identifies their causes. A semi-analytical simulation based on the rain gauge mechanism response to rainfall intensity has been developed in laboratory and contrasted with the standardized dynamic calibration and conventional static calibration, through a root-mean-square error analysis, using two different tipping bucket rain gauge models. Thus, two major sources of underestimation have been recognized: one due to the cumulative water lost during tipping movement and the other due to the surplus water contributed by the critical drop. Furthermore, a random variation, unrelated to rainfall intensity, was also observed, and three regions in the calibration curve were described.