A Numerical Study of a Dynamically Induced Foehn Observed in the Abashiri-Ohmu Area
نویسنده
چکیده
Observations are given for the foehn event which occurred in the Abashiri-Ohmu area (N44.3, E143.5), Hokkaido, northern Japan, on 12 May 1975. A numerical investigation is made of the foehn, using a 2-dimensional nonhydrostatic model. The foehn is well simulated, even without any diabatic heating in the presence of an inversion layer below 900hPa. This foehn is confirmed to be dynamically induced, and is an unsteady, highly nonlinear phenomenon. It is accompanied by an atmospheric bore (a shock-like disturbance propagating upstream) and an internal hydraulic jump (a shock-like disturbance propagating downstream), but no wave breaking (wave induced critical layer). The foehn of a homogeneous fluid (with constant mean velocity U and constant Brunt-Vaisala frequency N) is also simulated. It is accompanied by wave breaking and hydraulic jump, but no bore. A foehn index (a non-dimensionalized potential temperature rise on the lee slope) is introduced, and its dependence on the inverse Froude number (Nh/U) is examined for the 4-layered fluid of the Abashiri-Ohmu case and the homogeneous fluid. The critical mountain height for the occurrence of the foehn is found to be lower in the presence of an inversion layer below 900hPa than in the absence of an inversion layer. In addition, the foehn event in the Abashiri-Ohmu area is compared with that of the European Alps
منابع مشابه
Experimental and numerical investigation of unsteady flow around cylinder with four plates perpendicular to it with the rotational degree of freedom
In this study, the behavior of a subject consisting of a cylinder with 4 plates perpendicular to it with a rotational degree of freedom under airflow both through the numerical approach, known as improved discrete vortex and experimental approach were investigated. The experimental and numerical results have shown that oscillating regime occurs in low velocity and length. This movement is vibra...
متن کاملFire danger anomalies associated with foehn-like winds in southeastern Australia
In southeastern Australia the synoptic archetypical severe fire weather day is that of the dry “cool change”, or coastally modified cold front. Less well known, however, are synoptic cases that occur in connection with the topography of the eastern Australian mainland and Tasmania, which can also lead to abrupt spatiotemporal changes in fire weather variables that ultimately result in locally e...
متن کاملFeasibility study of underground salt caverns in Western Newfoundland: experimental and finite element investigation of creep-induced damage
Underground caverns in rock salt deposits are the most secure disposal method and a type of gas-storing facility. Gas storage plays a vital role in ensuring that a strategic relationship is secured between an established energy infrastructure provider and a midstream energy company. The Fischells Brook area is a pillow-shaped body of salts located in the St. George's Bay area of southwest Newfo...
متن کاملSwiss and Austrian Foehn revisited: A Lagrangian-based analysis
Two different South Foehn types have been described in the literature: the Swiss Foehn is characterized by significant ascent on the southern side of the Alps, hence fulfilling a requirement of the thermodynamic Foehn theory associated with latent heating. On contrast, the Austrian Foehn is characterized by near-horizontal flow to the south of the Alps, followed by dry-adiabatic descent into th...
متن کاملThreat-Independent Column Removal and Fire-Induced Progressive Collapse: Numerical Study and Comparison
Progressive collapse is defined as the spread of an initial failure from element to element, eventually resulting in the collapse of an entire structure or a disproportionately large part of it. The current progressive collapse analyses and design methods in guidelines and codes focus on the alternate load path method. This method is suitable especially in the case of blast-induced progressive ...
متن کامل