Analysis of single-Alter-shielded and unshielded measurements of mixed and solid precipitation from WMO-SPICE

Abstract

Abstract. Although precipitation has been measured for many centuries, precipitation measurements are still beset with significant inaccuracies. Solid precipitation is particularly difficult to measure accurately, and wintertime precipitation measurement biases between different observing networks or different regions can exceed 100 %. Using precipitation gauge results from the World Meteorological Organization Solid Precipitation Intercomparison Experiment (WMO-SPICE), errors in precipitation measurement caused by gauge uncertainty, spatial variability in precipitation, hydrometeor type, crystal habit, and wind were quantified. The methods used to calculate gauge catch efficiency and correct known biases are described. Adjustments, in the form of "transfer functions" that describe catch efficiency as a function of air temperature and wind speed, were derived using measurements from eight separate WMO-SPICE sites for both unshielded and single-Alter-shielded precipitationweighing gauges. For the unshielded gauges, the average undercatch for all eight sites was 0.50 mm h −1 (34 %), and for the single-Alter-shielded gauges it was 0.35 mm h −1 (24 %). After adjustment, the mean bias for both the unshielded and single-Alter measurements was within 0.03 mm h −1 (2 %) of zero. The use of multiple sites to derive such adjustments makes these results unique and more broadly applicable to other sites with various climatic conditions. In addition, errors associated with the use of a single transfer function to correct gauge undercatch at multiple sites were estimated.

Adjustment of measurement errors to reconcile precipitation distribution in the high‐altitude Indus basin

“…However, it is also gauge/shield-specific and different site specificities and gauge/shield configurations might result in different adjustment functions. Kochendorfer et al (2017a) analysed precipitation measurements from eight different WMO-SPICE sites for both unshielded and single-Alter-shielded OTT Pluvio 2 and Geonor T-200B3 types of weighing gauges. They grouped unshielded and single-Alter-shielded precipitation gauge configurations separately irrespective of gauge types and created a single transfer function of air temperature and wind speed using the corresponding measurements from the reference gauge.…”

“…where T air is mean air temperature ( C), U is wind speed (m/s), a, b and c are the coefficients fit to the data and TAN −1 is the inverse of tangent function. Our method of adjusting systematic errors in precipitation measurements largely follows the approach by Adam and Lettenmaier (2003) using the "liquid" part of the model by Legates (1987) and uses the model by Kochendorfer et al (2017a) for adjustment of the solid precipitation component. The detailed methods for computation of the required variables in Equation (1) are described in the supplement available on-line.…”

“…The detailed methods for computation of the required variables in Equation (1) are described in the supplement available on-line. The coefficient values in Equation (2) (a = 0.0623, b = 0.776, c = 0.431) are taken as determined at 10 m height by Kochendorfer et al (2017a). We used the coefficient values of 10 m height because most of our wind speed data belonged to the JRA55 data set, which provides wind speed data at 10 m height.…”

An Overview of Surface-Based Precipitation Observations at Environment and Climate Change Canada

“…The responses of several gauge and shield configurations were studied operationally under certain environmental conditions. Transfer functions were developed to adjust gauge measurements, specific to individual configurations and climate regimes using available overlapping reference gauges and ancillary measurements (wind, temperature, and precipitation type; Kochendorfer, Nitu, et al, 2017;Wolff et al, 2015;Wong, 2012;Yang, 2014).…”

Multi‐scale evaluation of a linear model of orographic precipitation over Sierra de Guadarrama (Iberian Central System)

“…Representativeness depends on many factors and rain gauge measurements often need extra corrections (Goodison et al, 1989;Groisman and Legates, 1994;Sevruk, 1996;Sevruk et al, 2009;Cheval et al, 2011;Isotta et al, 2015). For unshielded gauges, an average undercatch for alpine areas has been found to be around 34% (Kochendorfer et al, 2017).…”