Testing and development of transfer functions for weighing precipitation gauges in WMO-SPICE

Weighing precipitationgauges are used widely for the measurement of all forms of precipitation, and are typically more accurate than tipping-bucket precipitationgauges. This is especially true for the measurement of solid precipitation; however, weighing precipitationgauge measurements must still be adjusted for undercatch in snowy, windy conditions. In WMO-SPICE (World Meteorological Organization Solid PrecipitationInterComparison Experiment), different types of weighing precipitationgauges and shieldswere compared, and adjustments were determined for the undercatch of solid precipitationcaused by wind. For the various combinations of gauges and shields, adjustments using both new and previously existing transfer functionswere evaluated. For most of the gauge and shieldcombinations, previously derived transfer functionswere found to perform as well as those more recently derived. This indicates that wind shieldtype (or lack thereof) is more important in determining the magnitude of wind-induced undercatch than the type of weighing precipitationgauge. It also demonstrates the potential for widespread use of the previously developed transfer functions. Another overarching result was that, in general, the more effective shields, which were associated with smaller unadjusted errors, also produced more accurate measurements after adjustment. This indicates that although transfer functionscan effectively reduce measurement biases, effective wind shieldingis still required for the most accurate measurement of solid precipitation.