Dew keeps deserts alive

Condensation of the atmospheric vapor into water occurs in nature near ground surface in two different forms: fog and dew. While for the formation of fog a high relative humidity (in practice close to 100%) is necessary, the formation of dew requires a cold well-insulated surface and air-saturation is not necessary. Precipitation in deserts tends to be episodic and localized, with aridity erratically interrupted by torrential rains. Although rainfall exceeds in quantity other forms of precipitation, it is dew which is the main source of water available for plants and animals. The present investigations on dew are oriented mainly toward agricultural practices and to some extent toward water recovery from dew. An investigation of arid natural ecosystems requires the information concerning water and the thermal regime of the soil and the atmospheric boundary layer. To fulfil this requirement, an improvement of in-situ measuring techniques relevant for harsh climatic and soil moisture conditions of deserts and development of monitoring systems, including remote sensing techniques, are necessary. There are inherent characteristics of the desert environment to which life in the desert has adapted. Any change in the dew and fog regime caused by local or global human impact can easily destroy the fragile natural ecosystems created. Monitoring of all forms of precipitation, especially dew and fog, as well as both air and soil humidity can provide information necessary for environmental control of deserts.