Rain Catch under Wind and Vegetal Cover Effects

Abstract

Wind effects on a rain gauge can cause a significant underestimation of rainfall depths and contribute to the inconsistency in rainfall data. To reconstruct rainfall data requires a consistent method to quantify the undercatch. Although some empirical adjustment factors have been recommended, they are not generalized enough to reflect the variations of wind speed with respect to height. This paper presents a model by which the undercatch at an elevated rain gauge can be estimated by the logarithmic wind velocity profile and raindrop terminal velocity. Deficiency percentages of rain catch predicted by this model agree with field observations and recommended adjustment factors. This approach was further expanded to predict rain undercatch percentage due to vegetal coverage or other obstructions.