| Summary: | To better understand the role of mountains in lee cyclogenesis, two such cases which occurred during BASE (Beaufort and Arctic Storms Experiment) are simulated using the Mesoscale Compressible Community model (MC2). Both cases are shown to satisfy criteria for lee cyclogenesis, despite some ambiguity in its definition. The successful simulations reveal that lee cyclogenesis involves several processes: (1) formation of an upper-level short wave, (2) column stretching, (3) enhanced convergence and increased relative vorticity resulting from adiabatic warming, (4) latent heat release and, in one case, increased baroclinicity due to low-level blocking by topography. The results of sensitivity experiments indicate that removal of topography (latent heat) produces a stronger (weaker) lee cyclone. Topography significantly influences the distribution of precipitation with climatological consequences for areas in the lee. It is found that cyclogenesis can still occur in the absence of mountains in the two cases studied, although mountains modify the cyclogenetic processes.
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