Subjective Analysis of Mesoscale Flow Patterns in Northern Israel

D. Skibin Nuclear Research Center-Negev, Beer Sheva, Israel

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A. Hod Nuclear Research Center-Negev, Beer Sheva, Israel

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Abstract

The average flow over northern Israel in July has been analyzed. Three-hourly maps of the flow were obtained and discussed. The synoptic pressure distribution is relatively invariable in this period. Therefore, the flow changes mainly through the action of mesoscale and microscale processes. The land-sea temperature differences and the topography are the main factors which influence the flow. The effects of topography are anticyclonic curvature of the flow as it passes the mountains; downslope flow during the night; creation of convergence zones during the morning due to differential heating of the ground; and the absence of a sea breeze “front.” Other minor influences are the land and sea breeze circulations over the Sea of Galilee and the Dead Sea, urban effects of large metropolitan areas and the geometry of the Mediterranean coast. The clutching mechanism between surface and upper air flow during early morning is suggested to explain changes in the flow direction and speed. The relative importance of these influences and their changes with time are seen in the analyzed flow.

The results of this analysis can be used as a basis for numerical studies of mesoscale circulations. It is concluded that such circulations, especially the existence of convergence and divergence zones and the vertical flow separation, may be very important in relation to siting of pollution sources. Thus, they should be incorporated into the siting procedure, in addition to local wind and pollution roses.

Abstract

The average flow over northern Israel in July has been analyzed. Three-hourly maps of the flow were obtained and discussed. The synoptic pressure distribution is relatively invariable in this period. Therefore, the flow changes mainly through the action of mesoscale and microscale processes. The land-sea temperature differences and the topography are the main factors which influence the flow. The effects of topography are anticyclonic curvature of the flow as it passes the mountains; downslope flow during the night; creation of convergence zones during the morning due to differential heating of the ground; and the absence of a sea breeze “front.” Other minor influences are the land and sea breeze circulations over the Sea of Galilee and the Dead Sea, urban effects of large metropolitan areas and the geometry of the Mediterranean coast. The clutching mechanism between surface and upper air flow during early morning is suggested to explain changes in the flow direction and speed. The relative importance of these influences and their changes with time are seen in the analyzed flow.

The results of this analysis can be used as a basis for numerical studies of mesoscale circulations. It is concluded that such circulations, especially the existence of convergence and divergence zones and the vertical flow separation, may be very important in relation to siting of pollution sources. Thus, they should be incorporated into the siting procedure, in addition to local wind and pollution roses.

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