Quantification of Sampling Errors of Tipping-Bucket Rain Gauge Measurements

Investigators 

Emad Habib, Witold Krajewski, and Anton Kruger

Overview

Despite recent advances in the use of remote sensing techniques for measuring rainfall, traditional rain gauges, such as Tipping-Bucket (TB) gauges, are still widely used in various hydrological and climatological applications. However, it is recognized that TB gauges suffer from several sources of uncertainty -- both systematic and random. The current study investigated sampling-related errors of the TB rain gauge measurements, focusing on the gauges ability to represent the small-scale rainfall temporal variability. TB observations are simulated using ultra-high resolution measurements from an experimental optical rain gauge (ORG) that is part of the IIHR weather station. The simulated observations were used to provide TB rain rate estimates on time scales as low as one minute. The simulation results showed that the TB estimates suffer from significant errors if based on time scales less than 10 to 15 minutes. The errors are more significant at low rain rates. The study shows the importance of using fine resolution of both the sampling time interval (5 seconds) and the bucket size (0.01 inches) so that the TB rain rate estimates have minimum levels of uncertainty. For practical applications, the study provided approximate formulae that can be used to characterize the TB sampling errors at several time scales.

Related publications 

Habib, E., W.F. Krajewski, and A. Kruger, "Sampling Errors of Tipping-Bucket Rain Gauge Measurements", ASCE Journal of Hydrologic Engineering, 159-166, March/April, 2001.