Dynamics Of The Dead Sea Planetary Boundary Layer Employing High Resolution Measurements And WRF Model

RAL Seminar Series

Aug. 15, 2019

2:00 pm MDT

NCAR Foothills Lab - building FL2, room 1001
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The Dead Sea (DS) valley is unique in the world because it is the lowest place on land (430 below MSL) and the very saline water body (DS) in its center. It is important to study the atmospheric circulation and be able to forecast the extreme weather conditions because of their influence on the population and the ecological system in the area.

In this seminar I will present a recent study that focused on the Mediterranean Sea Breeze (MSB) arrival to the DS valley during evening hours. Motivated by the significant interdaily variability, we investigated two events that differ in the influence of the MSB on the local DS valley circulation, characterized by steep changes in moisture, temperature and wind at the surface and along the planetary boundary layer.

Unique very high-resolution (HR, both vertical and temporal) observations first conducted in the DS valley as part of the Virtual Institute DEad SEa Research Venue (DESERVE) together with HR WRF model simulations were used in this study.

The observations included the KITcube instruments (a ground-based microwave radiometer, two wind lidars and radiosoundings) along with Energy Balance Stations. These provided horizontal and vertical winds, temperature, humidity, pressure, radiation, and visibility data.

WRF model was configured with four nested domain with 30, 10, 3.3 and 1.1 km grid spacing. The WRF model sensitivity was checked for: (1) landuse/vegetation databases, (2) PBL schemes, (3) number of vertical levels, (4) atmospheric and soil initial and lateral boundary conditions from different global models, (5) source of initial conditions for the finest domain, (6) initialization times of coarse domains and (7) initialization times of finest domain. After evaluation against the HR observations, results from the optimal WRF configuration were used to analyze the chosen events.

It was found that the foehn wind phenomena developed along with the MSB descent from the mountains down to the DS valley and the weakening of opposing upward winds on the lee side. The foehn characteristics on both events, including the associated hydraulic jump, were influenced by the synoptic and mesoscale conditions.

The feasibility of forecasting foehn and the sudden temperature, moisture and wind changes in the DS valley 24 hours in advance is suggested following the present study. These forecasts can be most valuable during high pollution events.

Dr. Dorita Rostkier-Edelstein, Hebrew University of Jerusalem