Wind-driven rain and driving rain coefficient during thunderstorms and non-thunderstorms

Water leakage of building envelopes is the result of wind and rain acting on the build faces. A good understanding of the wind-driven rain phenomenon will help to overcome water-leakage problems as well as other issues such as staining and drainage on building facade. This paper presents the results of observations of a wind-driven rain-measuring station in Singapore. It first gives a description of the station which monitors the wind, rain and wind-driven rain. Analyses are carried out on measurements taken during thunderstorm and non-thunderstorm rain events to obtain their characteristics. Studies on the variation of wind-driven rain intensity with averaging period are carried out. Results indicate that the short duration intensity can be 10-20 times the hourly average. The relationship between wind, rain and the wind-driven rain intensity is also investigated. Study of the driving-rain intensity coefficient indicates that the ideal coefficient calculated based on drop size distribution is not appropriate for low altitudes close to the ground. The actual coefficient is 1.5-2.2 times the ideal value. (C) 2001 Elsevier Science Ltd. All rights reserved.