Fog precipitation on the Island of Madeira (Portugal)

An important aspect of the Madeira Island's climate is its persistent nebulous covering mainly of orographic origin, which normally exists between the 600-800- to 1,600-m altitude. The object of this study is to quantify the amount of water that can be gathered by direct interception from clouds. The first results at the end of 2 years were higher than expected. The daily rates of the 'standard fog collector' ranged between 6.0 to 21.3 l/m(2) of vertical collecting surface. The water collected by the rain gauges beneath Erica arborea L., ranged between 33.3 to 56.4 mm of water per day (l/m(2) per day). Depending on wind direction and speed, which is normally north-east, the highest fog water production can be 250 mm/day. Fog drip under the vegetation was three and a half times greater than the annual precipitation.