Dew deposition across a longitudinal sand dune with biological crusting, Negev desert, Israel

Abstract: In a desert, dew can serve as a source of moisture for small animals, plants, and biological crust development. Parts of desert dunes can consist of a thin crust layer on the sandy surface, which is formed by biological activity. The existence of such a layer is very important as it can initiate or enhance the stability of sand dunes. The goal of the present research is to assess dew-fall along a 200 m long transect running between 2 longitudinal sand dunes in the northern Negev desert, Israel. In September 1997, a measurement programme was carried out in which the energy budget at the biological crust layer was measured. Here, special attention was focussed on the nighttime (dew-fall period) and early morning (drying period) sensible and latent heat transports. With the eddy correlation technique both convective transports are estimated in a direct way. At the surface, with a number of small micro lysimeters, the water budget of the first 2 cm depth of the ground, including the biological crust layer, is observed. Moreover, with an optical remote dew sensor the wetness of the surface is monitored continuously during the observing period. Model simulations are carried out and during the presentation, the model results as well as the analysed measurement results will be discussed.