Investigation of sea-breeze/foehn in the Dead Sea valley employing high resolution WRF and observations.

The penetration of the uniquely strong Mediterranean Sea Breeze (MSB) into the Dead Sea (DS) valley has been studied for decades. However, the studies relied mostly on surface observations and coarse-model simulations. Motivated by the significant interdaily variability, we investigate two typical but different events: a frequent event in which the surface specific humidity (SH) steeply decreases and surface temperature increases during MSB penetration by ~40% and 1.2 °C, respectively; and a less frequent event, with almost the opposite behavior, an increase of surface SH by ~20%. Decrease in the integrated water vapor (IWV) content at MSB arrival is significantly larger in the first event. To reveal the factors responsible for these different behaviors we use high-resolution in–situ and remote-sensing observations, together with WRF simulations. It was found that foehn developed following the MSB descent down to the DS valley. The foehn characteristics were influenced by the synoptic and mesoscale conditions. While on the first event the foehn reached the surface of the valley, on the second it did not. This led to the different behavior of the surface temperature and SH. An additional factor was the amount of moisture brought by the DS breeze and MSB. Different altitudes of stable layers led to the different changes of the IWV. Our simulations suggest the feasibility of forecasting foehn and sudden changes in surface variables in the DS valley 24 h in advance. These forecasts can be most valuable during high pollution events. • MSB/foehn penetration into Dead Sea valley using observations and WRF. • Two case studies show significant differences at the time of MSB arrival. • The surface SH decreased and surface temperature increased in the first event. • Opposite behavior of SH and temperature in the second event. • The differences were caused by different synoptic, mesoscale and local conditions. [ABSTRACT FROM AUTHOR]