Articles | Volume 21, issue 7
Hydrol. Earth Syst. Sci., 21, 3525–3542, 2017

Special issue: The World Meteorological Organization Solid Precipitation...

Hydrol. Earth Syst. Sci., 21, 3525–3542, 2017

Research article 14 Jul 2017

Research article | 14 Jul 2017

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

John Kochendorfer1, Rodica Nitu2,3, Mareile Wolff4, Eva Mekis2, Roy Rasmussen5, Bruce Baker1, Michael E. Earle6, Audrey Reverdin7, Kai Wong2, Craig D. Smith8, Daqing Yang8, Yves-Alain Roulet7, Samuel Buisan9, Timo Laine10, Gyuwon Lee11, Jose Luis C. Aceituno9, Javier Alastrué9, Ketil Isaksen4, Tilden Meyers1, Ragnar Brækkan4, Scott Landolt5, Al Jachcik5, and Antti Poikonen10 John Kochendorfer et al.
  • 1Atmospheric Turbulence and Diffusion Division, ARL, National Oceanic and Atmospheric Administration, Oak Ridge, TN, 37830, USA
  • 2Environment and Climate Change Canada, Toronto, ON, M3H 5T4, Canada
  • 3World Meteorological Organization, Geneva, 1211, Switzerland
  • 4Norwegian Meteorological Institute, Oslo, 0313, Norway
  • 5National Center for Atmospheric Research, Boulder, 80305, USA
  • 6Environment and Climate Change Canada, Dartmouth, Nova Scotia, B2Y 2N6, Canada
  • 7Meteoswiss, Payerne, 1530, Switzerland
  • 8Environment and Climate Change Canada, Saskatoon, SK S7N 3H5, Canada
  • 9Delegación Territorial de AEMET (Spanish National Meteorological Agency) en Aragón, Zaragoza, 50007, Spain
  • 10Finnish Meteorological Institute, Helsinki, 00101, Finland
  • 11Kyungpook National University, Daegu, 41566, Korea

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 precipitation-weighing 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.

Short summary
Precipitation measurements were combined from eight separate precipitation testbeds to create multi-site transfer functions for the correction of unshielded and single-Alter-shielded precipitation gauge measurements. Site-specific errors and more universally applicable corrections were created from these WMO-SPICE measurements. The importance and magnitude of such wind speed corrections were demonstrated.