H. Shafir

Mesoγ-Scale Distribution of Orographic Precipitation: Numerical Study and Comparison with Precipitation Derived from Radar Measurements

Abstract On the assumption that moisture convergence due to mechanical uplifting approximately equals the orographic precipitation, the mesoγ-scale rainfall distributions over mountainous regions in Israel are investigated. The simulated distributions are compared to rainfall observations both from raingages and from radar reflectivities. The mean error in the predicted rainfall on scale of 2 km was ±8.4% for mean annual normals and 15%–20% for three case studies. It is suggest that orographic rainfall on the small mesoscale is highly predictable with the adiabatic assumption that the uplifting is determined by V·ΔZs, where V is the horizontal wind encountering the mountain and Zs, is the topographic elevation. It is also illustrated that the climatological observed rainfall distribution could be complemented by the model at locations where sufficient observations were not available. By comparison of the model simulation with the radar-derived rainfall, the considerable effect that a change in the wind di...

A Dust Prediction System with TOMS Initialization

Abstract A dust prediction system, developed earlier at the University of Athens within the framework of the Mediterranean Dust Experiment (MEDUSE) project, was enhanced at Tel Aviv University to support the Israeli–American Mediterranean Israeli Dust Experiment (MEIDEX) project. These enhancements include development of a dust initialization approach using Total Ozone Mapping Spectrometer (TOMS) aerosol index (AI) data and improved specification of the dust sources. The skill of the model against the TOMS AI measurements was tested during two periods in March and June 2000 using four different scores. It is shown that the TOMS-based initialization has a significant positive impact on all the scores. For instance, the average distance between the predicted and TOMS-observed dust plumes drops from 350–485 to less than 200 km. Verification of model forecasts against surface dust measurements in Tel Aviv shows correlations of up to 0.69 based on 27 predictions, for both 24 and 48 h. One example of a narrow d...

Climatic-related Evaluations of the Summer Peak-Hours' Electric Load in Israel

Abstract The interrelationship between the Summer peak electric load in Israel and pertinent meteorological parameters, including the commonly used outdoor biometeorological comfort index, is evaluated conceptually and statistically. Linear regression that was established between the peak electric load and these parameters indicated high correlation for the comfort index. Estimation of climatic change impact on the summer peak electric load indicated (i) mild effects as a result of changes in land use, and (ii) noticeable long-term changes due to potential climatic change associated with doubling of the atmospheric CO2.

Orographic Precipitation Simulated by a Super-High Resolution Global Climate Model over the Middle East

A super-high resolution (20 km) global climate model data and Climate Research Unit (CRU) data were employed to investigate the seasonal precipitation regime over the Middle East, and the main research focus is on the orographic rainfall effects over a large part of Turkey by using these two different datasets.

Wind Channeling by the Dead-Sea Wadis

Wind channeling by small wadis of few kilometers width at the Dead-Sea area is demonstrated with high- resolution modeling. Previous works have not shown such channeling in very small rivers due to computation difficulties on the meso-� and the lack of suitable observations for verification. The wind channeling is demonstrated in three wadis, and was verified by meteorological model simulations on the meso-� scale, as well as by surface and upper layers obser- vations. There are two dominant mechanisms for the wind channeling, the geometrical forcing and the thermal katabatic effect as shown by the model negative divergence zone inside the wadis. The unique features of the Dead-Sea i.e., the ab- sence of vegetation cover and urban areas can serve as a proposed natural model for the wind-wadi interaction.