Numerical Simulations of the 1994 Piedmont Flood: Role of Orography and Moist Processes

Buzzi, A.; Tartaglione, Nazario; Malguzzi, P.

doi:10.1175/1520-0493(1998)126<2369:nsotpf>2.0.co;2

Cited by 210 publications

(190 citation statements)

References 9 publications

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“…Orographic lifting has been largely proposed in past studies as a mechanism for triggering heavy precipitation events over the western Mediterranean (e.g. Smith, 1979;Houze, 1993;Lin, 1993;Buzzi et al, 1998;Buzzi and Foschini, 2000;Lin et al, 2001;Rotunno and Ferretti, 2001;Pradier et al, 2002;Bousquet and Smull, 2003;Georgis et al, 2003 among others). Whereas precipitation formation induced by uplift of a stably stratified flow over a mountain ridge has been thoroughly investigated in idealized numerical frameworks, few studies have been devoted to the more challenging issue of a conditionally unstable flow impinging on a mountain range.…”

Section: Introductionmentioning

confidence: 99%

Idealized numerical simulations of quasi‐stationary convective systems over the Northwestern Mediterranean complex terrain

Bresson

Ducrocq

Nuissier

et al. 2012

Quart J Royal Meteoro Soc

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Northwestern Mediterranean coastal regions are frequently affected by torrential rainfall associated with quasi-stationary mesoscale convective systems (MCSs). The present work examines how the characteristics of a conditionally unstable flow impinging on the coastal complex terrain of the Northwestern Mediterranean can affect the location and intensity of quasi-stationary MCSs. The study is based on idealized simulations, but including the major ingredients of Northwestern Mediterranean heavy precipitation events: a moist conditionally unstable marine flow of about 100 km width facing the true terrain, composed of the Massif Central surrounded by the Alps and the Pyrenees.We find that MCSs are located upstream of the mountain range with a slow flow, whereas with a rapid flow the heaviest precipitation is over the Massif Central slopes. In a similar way, when the lateral environment is drier the heaviest precipitation is located upstream whereas a humid environment favours precipitation over the slopes. The dominant lifting mechanism is strongly related to the location of the system: (1) direct orographic triggering for systems over mountain slopes and (2) cold-pool triggering for upstream systems. In addition, the neighbouring mountains interplay through deflection of the flow and induced low-level convergence favoured by slow or dry lateral environments and through cold-pool blocking within valleys. Copyright c 2012 Royal Meteorological SocietyKey Words: deep convection; heavy precipitation; mesoscale processes

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Section: Introductionmentioning

confidence: 99%

Idealized numerical simulations of quasi‐stationary convective systems over the Northwestern Mediterranean complex terrain

Bresson

Ducrocq

Nuissier

et al. 2012

Quart J Royal Meteoro Soc

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“…The sea provides the moisture supply to the moderate to strong, southerly to easterly, low-level flow that feeds the heavy precipitation events. The role of sensible and latent-heat fluxes from the Mediterranean Sea has been investigated by Buzzi et al (1998) for the Piedmont flood event (1994). They found for their case-study that the Mediterranean mainly modulates the intensity and not the location of the convective precipitation.…”

Section: Introductionmentioning

confidence: 99%

“…Besides, the role of orography in triggering heavy precipitation over western Mediterranean regions has been well documented (e.g. Smith, 1979;Houze, 1993;Lin, 1993;Buzzi et al, 1998;Buzzi and Foschini, 2000;Lin 132 V. DUCROCQ ET AL. et al, 2001;Rotunno and Ferretti, 2001;Pradier et al, 2002;Bousquet and Smull, 2003;Georgis et al, 2003, among others).…”

Section: Introductionmentioning

confidence: 99%

“…Considering both synoptic-scale forced and unforced cases, recent numerical studies (Buzzi et al, 1998;Ferretti et al, 2002;Stein, 2002) have emphasized that suppression of orography significantly reduces total simulated rainfall, clearly showing the orography as the first-order cause of floods. Buzzi et al (1998) emphasized the feedback between latent heat release and orographic forcing that can determine the type of orographic flow regime (via 'effective' Froude number changes), thus influencing the larger-scale flow. Other studies also insist on the role played by the low-level convergence in producing heavy precipitation.…”

Section: Introductionmentioning

confidence: 99%

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A numerical study of three catastrophic precipitating events over southern France. II: Mesoscale triggering and stationarity factors

Ducrocq

Nuissier

Ricard

et al. 2008

Quart J Royal Meteoro Soc

196

200

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ABSTRACT:In the western Mediterranean basin, large amounts of precipitation can accumulate in less than a day when a Mesoscale Convective System (MCS) stays over the same area for several hours. Heavy Precipitating Events (HPEs) in this region (especially southern France) are not only characterized by significant precipitation rates (typically more than 200 mm in less than 24 or 48 hours) but also by quasi-stationary behaviour. The aim of this present study is to use realistic simulations of past events to analyze and better understand the physical mechanisms which lead to the stationarity of HPEs over southern France using a high-resolution (2.5 km) non-hydrostatic mesoscale atmospheric model. We focused on three

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“…In addition to these observational studies, there are multiple theoretical experiments that describe the inverse relationship between the Froude number and the degree of frontal retardation (e.g., Egger and Hoinka 1992). Furthermore, several studies have used numerical simulations with and without topography to evaluate the role of terrain (e.g., Buzzi et al 1998;Rotunno and Ferretti 2001).…”

Section: Introductionmentioning

confidence: 99%

Effect of the Andes Cordillera on Precipitation from a Midlatitude Cold Front

Barrett

Garreaud

Falvey

2009

Monthly Weather Review

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The effects of the Andes Cordillera, the major mountain range in South America, on precipitation patterns of baroclinic systems approaching from the southeast Pacific remain largely unstudied. This study focuses on a case in late May 2008 when an upper-level trough and surface cold front produced widespread precipitation in central Chile. The primary goal was to analyze the physical mechanisms responsible for the structure and evolution of the precipitation.Weather Research and Forecasting (WRF) model simulations indicate that as an upper-level trough approached central Chile, midtropospheric flow below 700 hPa was blocked by the high topography and deflected poleward in the form of a barrier jet. This northerly jet had wind maxima in excess of 15 m s 21 , was centered around 925 hPa, and extended westward 200 km from the mountains. It intersected the cold front, which approached from the south near the coast, thereby increasing convergence along the frontal surface, slowing its equatorward progress, and enhancing rainfall over central Chile. Another separate region of heavy precipitation formed over the upwind slopes of the cordillera. A trajectory analysis confirmed that the barrier jet moved low-level parcels from their origin in the moist southeast Pacific boundary layer to the coast. When model topography was reduced to twenty percent of its original height, the cold front advanced more rapidly to the northeast, generated less precipitation in central Chile between 338 and 368S, and produced minimal orographic precipitation on the upwind Andean slopes. Based on these findings, the high topography appears responsible for not only orographic precipitation but also for substantially increasing precipitation totals over the central coast and valley.

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Numerical Simulations of the 1994 Piedmont Flood: Role of Orography and Moist Processes

Cited by 210 publications

References 9 publications

Idealized numerical simulations of quasi‐stationary convective systems over the Northwestern Mediterranean complex terrain

Idealized numerical simulations of quasi‐stationary convective systems over the Northwestern Mediterranean complex terrain

A numerical study of three catastrophic precipitating events over southern France. II: Mesoscale triggering and stationarity factors

Effect of the Andes Cordillera on Precipitation from a Midlatitude Cold Front

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