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.