MODELING OF WIND-TUNNEL MEASUREMENTS OF PRECIPITATION GAUGES

Wind-induced loss constitutes the greatest systematic error of precipi tation measurements and its assessment is a problem of major concern. This paper deals with some aspects of wind-flow deformation around pre cipitation gauges. A number of wind-tunnel measurements are analysed w ith the aim of determining a gauge characteristic scale length and a s uitable value for the reference velocity for normalizing vertical velo city profiles, used for intercomparison of different precipitation gau ges. For this purpose, the outer diameter of the gauge and the measure d velocity value taken from a height of twice the outer diameter and d ivided by 1.0225 are recommended. The flow around the Mk2 gauge has be en numerically simulated and intercomparisons with measurements show p romising agreement.