J. Egger et al., NUMERICAL EXPERIMENTS ON THE GENESIS OF SHARAV CYCLONES - IDEALIZED SIMULATIONS, Tellus. Series A, Dynamic meteorology and oceanography, 47(2), 1995, pp. 162-174
A three-level channel flow model is used to investigate the generation
of Sharav cyclones in the lee of the Atlas mountains through ''ideali
zed'' numerical experimentation. A typical initial state consists of a
barotropic high-low system, embedded in baroclinic shear flow and cen
tered to the north of the Atlas mountains. If this ''perturbation'' is
of sufficient strength, a cold-air outbreak occurs in the rear of the
low as well as a southward excursion of the trough at upper levels. T
he cold air is blocked by the Atlas mountains, if the initial location
of the low is chosen properly. The upper-level trough intensifies sli
ghtly when crossing the mountain range and induces then a low-level cy
clone in the lee. The trough turns eastward later on and the new cyclo
ne is staying close to this upper-level centre. A simple two-dimension
al three-layer model is used to explain salient features of this type
of lee cyclogenesis. Moreover, additional experiments are conducted in
order to elucidate details of the cyclogenetic process.