Lake Kinneret (Sea of Galilee) and its exceptional wind system

From 1973–1976, research was performed around the Sea of Galilee, aimed at examining the wind regime in the area and whether the area develops a land-sea breeze despite its particular topographical location.

The main conclusions were:
1. During the summer mornings a lake breeze develops, blowing towards the shores of the lake. It ceases at the peak of its development when a westerly wind, originating in the development of a breeze along the Israeli Mediterranean coast, plunges towards the lake.
2. Late at night, a wind flow develops from the land towards the lake, which combines with the katabatic winds that blow along the steep slopes surrounding the Kinneret.
3. The stations at the upper level, at a height of 400–500 m above the Kinneret, are not affected by the lake breeze during the day or by the land breeze at night.
4. In winter, the Kinneret lake breeze is almost as developed as in summer, because the westerly winds, originating in the Mediterranean sea breeze which hardly develops in this season, do not plunge into the Kinneret.

     

Planning and climate — The case of Di-Zahav

Climate is one of the important factors which must be taken into consideration in all levels of planning. Despite its importance many planners are still unaware of it. An excellent example of such a situation is the case of Di-Zahav, a new settlement located about 130km south of Elat, on the alluvial fan of Wadi Dahab, which flows to the Gulf of Elat.In addition to its extreme hot and arid climate, the region suffers from very strong winds blowing throughout the year from the northerly direction. Heavy rainfall on the 19—20 February 1975 caused a considerable flood in the Wadi Dahab. Because of a mistake in the construction of the road leading to Di-Zahav, the settlement was inundated. After the water dried up, the strong north winds blew sand and dust into the village and dunes accumulated between the buildings. The strong winds are also a negative factor in human comfort and are an obstacle in the development of tourism which is the economic basis of Di-Zahav. Therefore, it seems that the location of the settlement on the southern part of the alluvial fan instead of on the north-eastern edge was a mistake. Also the detailed plan did not take into consideration the negative effects of the climate. It was therefore necessary to plan and carry out a peripheral and internal protection system consisting of planted and artificial windbreaks. It was also suggested to carry out some modifications in the buildings in order to prevent the strong winds blowing into them.     

Climatological aspects in locating settlements in arid regionsKlimatologische aspekte bei der standortwahl für neue siedlungen in ariden regionenAspects climatologiques dans l'emplacement de villages dans des régions arides

In arid and semi-arid regions it is important to pay attention to climatic factors in locating and planning new settlements. Physical factors such as large differences in elevation over short distances, proximity to a large lake or the combination of the two factors, cause improvement of the climate.The central Jordan Valley and the Dead Sea could be a suitable area for proving these assumptions. A topo-climatological research has been performed in this region to help the planners in finding the best locations for new settlements. By using a “discomfort index”, which is based on temperature and humidity, the influence of the above mentioned physical factors on local climate modification has been verified. Also, its importance in the improvement of the location of new settlements has been shown.     

Explicit adaptive symplectic integrators for solving Hamiltonian systems

We consider Sundman and Poincaré transformations for the long-time numerical integration of Hamiltonian systems whose evolution occurs at different time scales. The transformed systems are numerically integrated using explicit symplectic methods. The schemes we consider are explicit symplectic methods with adaptive time steps and they generalise other methods from the literature, while exhibiting a high performance. The Sundman transformation can also be used on non-Hamiltonian systems while the Poincaré transformation can be used, in some cases, with more efficient symplectic integrators. The performance of both transformations with different symplectic methods is analysed on several numerical examples.     

A model for GRB jets

By using relativistic, axisymmetric, ideal MHD, we examine the motion of the baryon/e^±/ photon fluid that emanates from a stellar-mass compact object/debris-disk system (a common outcome of many progenitor models). We prove that the motion can be described as a frozen pulse, which permits the study of each shell of the pancake-shaped outflow using steady-state equations. The ejected energy flux is dominated by the electromagnetic (Poynting) contribution, but it can also have a non negligible e^±/radiation (thermal fireball)component. We demonstrate, through exact self-similar solutions, that the flow is first thermally and subsequently magnetically accelerated up to equipartition between kinetic and Poynting fluxes, i.e., ～ 50% of the total energy is converted into baryonic kinetic energy. The electromagnetic forces also collimate the flow, reaching a cylindrical structure asymptotically.     

Numerical Simulation of the Airflow Across Trees in a Windbreak

The flow across a three-dimensional (3-D) windbreak comprising individual cypress trees is studied to establish the significance and extent of the 3-D flow patterns. The cypress tree is modelled as a solid cylindrical stem and a conic porous canopy. Cases with a single row of trees or two rows of trees with different distances between the rows are considered; in the case of a single row, several densities of the canopy are used. The steady Reynolds-averaged Navier–Stokes (RANS) approximation is solved using a commercial computational fluid dynamics (CFD) package and a high-resolution mesh. Three-dimensional flow is found in the vicinity of the windbreak up to a leeward distance of 1–2 tree-heights, depending on the density of the canopy, and is manifest as significant lateral variations and reduced vertical flow. At larger leeward distances, a two-dimensional (2-D) flow is established with characteristics similar to existing 2-D studies; the flow leeward of the last row is insensitive to the distance between the rows. Homogeneous 2-D windbreak models are found to be inaccurate in the vicinity of the windbreak. This is exactly the region that needs to be sheltered in many cases, since the inner vegetation is anyway protected by the outer vegetation.