Vertical distribution of physical and chemical properties of haze particles in the Dead Sea valley

摘要

The chemical and physical properties of haze particles in the Dead Sea were measured using airborne and ground-based instruments. The results show a very distinct layering of the haze with two major layers, one below about 300 m ASL and the other at around -150m ASL, which is around +250m above the Dead Sea surface. The lower layer was found to contain a large fraction of sodium nitrate particles with sizes larger than 1 μm. The particles in this layer are likely transported at night from pollution sources to the south west of the Dead Sea. The upper layer contained large concentrations of fine sulfate particles that are transported from distance sources such as the Israeli Mediterranean coastal regions or even from sources as far away as Europe. The two haze layers appear to be separated in the morning hours, but as the day marches on and the temperature of the land surface on both sides of the lake increases, thermal convection sets in and the two layers become homogenized. A third layer around 1000m ASL is also observed. This layer is the commonly observed marine boundary layer over Israel and is not affected by the circulation in and around the Dead Sea. In the afternoon the Mediterranean sea breeze reaches the Dead Sea valley and is diverted first into a weak easterly and then into stronger northerly winds, which clear the haze particles from the valley. The land breeze over the lake during the night brings new pollution particles from the Rotem Plato to the southeast of the Dead Sea and is responsible for the formation of the early morning lower haze layer.