Biases and Errors in Weighing Gauge Precipitation Measurements

Precipitation measurements are used by policy makers, hydrologists, farmers, and watershed managers to quantify and allocate the water available for society's needs. Precipitation measurements are also necessary to understand our changing climate and for public safety in areas as diverse as flood forecasting, roadway safety, and aircraft de-icing operations. Although precipitation has been measured for many centuries, precipitation measurements are still beset with significant biases and errors. Solid precipitation is particularly difficult to measure accurately, and biases between winter-time precipitation measurements made using different technologies, different measurement networks, or different regions can be greater than 100%. To address these issues the WMO initiated the Solid Precipitation Intercomparison Experiment (SPICE). Using the reference precipitation gauge results from SPICE, the errors in precipitation measurement caused by gauge uncertainty, spatial variability and wind are quantified and discussed. In addition, the methods used to calculate gauge catch efficiency and correct known biases are described.