Abstract
In a series of papers, Miglietta and Rotunno reported on numerical simulations of conditionally unstable flows past an idealized mesoscale mountain ridge. These idealized simulations, which were performed with a three- dimensional, explicitly cloud-resolving model, allowed the investigation of simulated-precipitation characteristics as a function of the prescribed environment. The numerical solutions were carried out for a uniform wind flowing past a bell-shaped ridge and using an idealized unstable sounding with prescribed values of the relevant parameters. Dimensional analysis of the numerical solutions revealed that the simulated maximum nondimensional rainfall rate depends on five nondimensional parameters. In this talk I will report on recent work by Migletta and Rotunno in which these theoretical results are applied to observed cases of orographically forced convective rainfall including the Big Thompson Flood (1976, Colorado), the Oahu Flood (1974, Hawaii), and the Gard Flood (2002, France). Specifically, numerical simulations were carried out using observed and idealized soundings relevant to these cases but with idealized topography. It is found that using the observed soundings, but with idealized constant wind profiles, the simulated rain rates fit reasonably well within the previous theoretically derived parameter space for intense orographic convective rainfall. However, in order to reproduce larger rainfall amounts, in closer agreement with observations, in the first two cases it was necessary to initialize the sounding with a wind profile characterized by low-level flow towards the mountain with weak flow aloft (as observed). However for the Gard case, the situation was more complex and it was found to be unlikely that the situation can be reduced to a simple two-dimensional problem.
扫一扫
被折叠的 条评论
为什么被折叠?
到【灌水乐园】发言
