THE <i>MISTRAL</i> AND FOREST FIRES IN PROVENCE—CÔTE D'AZUR, SOUTHERN FRANCE

Wrathall, James E.

doi:10.1002/j.1477-8696.1985.tb07493.x

Cited by 9 publications

(5 citation statements)

References 4 publications

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“…The operation of several facilities there requires the controlling of pollutant emissions and the assessment of their impact. Clear skies and calm winds are regularly observed in the region (Wrathall, 1985), leading to the onset of locally driven winds in the complex area in and around Cadarache. Understanding the patterns of valley flows, their interactions, and cold‐air pool formation in the tributaries of the DV is therefore essential when evaluating the environmental impact of Cadarache's activities.…”

Section: Kascade Experimentsmentioning

confidence: 99%

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Characterization of valley flows within two confluent valleys under stable conditions: observations from the KASCADE field experiment

Duine

Hedde

Roubin

et al. 2017

Quart J Royal Meteoro Soc

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Wind patterns in main and tributary valley systems undergo diurnal variations that are very dependent on the valley's dimensions. Characterizing the down‐valley winds is important for pollutant dispersion studies. It is also a challenge for numerical simulations. This paper uses KASCADE (KAtabatic winds and Stability over CAdarache for Dispersion of Effluents) observations to describe down‐valley flow development and characteristics in two intersecting, shallow valleys of different sizes located in the pre‐alpine region of southeast France. The Durance Valley and its tributary valley, the Cadarache Valley, are different in depth (200 and 100 m depth, respectively), slope (0.2 and 1.2°), width (5–8 and 1–2 km) and length (>50 and 6 km). Both down‐valley flows were dominant features for the period of measurements. The distinct valley scales lead to different characteristics: the smaller Cadarache down‐valley wind is primarily thermally driven and attains wind speeds of up to 1–4 m s−1 with its jet nose at around 30 m in height above ground. The flow at that height initiates 2 h after sensible heat flux turnover, a time‐scale which relates to a linear wave solution for along‐valley winds. The Durance down‐valley wind involves larger scales –for both terrain features and large‐scale circulation –and is related to a mountain‐to‐plain circulation. Therefore its onset occurs with a delay of ∼6 h after sunset. It reaches speeds of 4–8 m s−1 and a depth of 175–225 m above ground. Its highest occurrence is just after sunrise. Between the two valley winds, a shear layer is observed, the origin of which could be a combination of a Cadarache valley flow return current and a Durance down‐valley wind stream redirected by orography.

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Section: Kascade Experimentsmentioning

confidence: 99%

“…Mistral) favour clear sky. Wrathall (1985) reported more than 2500 h of sunshine per year in the region.…”

Section: Kascade Experimentsmentioning

confidence: 99%

Characterization of valley flows within two confluent valleys under stable conditions: observations from the KASCADE field experiment

Duine

Hedde

Roubin

et al. 2017

Quart J Royal Meteoro Soc

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“…At finer scale, its dynamics over land has been investigated. The mistral mechanism was first described as cold air funneling through the Rhône valley, or fall wind [ Galzi , ; Gerbier and Berenger , ; Bordeuil et al , ; Mayençon , ; Wrathall , ]. Pettré [] described the mistral dynamics by the two‐dimensional reduced‐gravity shallow‐water theory, in which the flow under consideration is bounded by a free surface.…”

Section: Introductionmentioning

confidence: 99%

Lagrangian dynamics of the mistral during the HyMeX SOP2

et al. 2017

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The mistral refers to a severe wind blowing over the Gulf of Lions after being channeled in the Rhone valley. It influences the western Mediterranean climate as it brings cold and dry continental air over the warm western Mediterranean, generating intense air‐sea heat exchanges and sea surface cooling, inducing the formation of the western Mediterranean deep water that moves into the Atlantic Ocean. The mistral is frequently observed to extend as far as a few hundred kilometers from the coast, and its fine‐scale dynamics over the sea is still only partially understood as finely resolved observations in time and space are lacking. The boundary layer pressurized balloons (BLPB) developed by the Centre National d'Etudes Spatiales and deployed during HyMeX SOP2 allowed the Lagrangian documentation of the mistral events that occurred between beginning of February to mid‐March 2013. Analyzed in synergy with the AROME‐WMED weather forecast model, all the terms of the Lagrangian formulation of the momentum conservation equation could be quantified showing three different regions: (1) an injection zone where the mistral flow is directed toward the center of the Genoa cyclone due to a strong zonal pressure gradient, enhanced friction, and entrainment in the mountain wake; (2) an ejection zone where the flow is deflected outward of the cyclone due to either the nonnegligible inertia pseudoforce or an inertial oscillation caused by a sudden friction decrease; and (3) a region of geostrophic deceleration due to the weakening of the pressure gradient.

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“…During summer, it accelerates ground drying and is responsible for the propagation of devastating forest fires (Wrathall, 1985). It accompanies cold and dry continental air masses and restores clear sky conditions after the passage of a cold front over Provence (south-eastern France).…”

Section: Introductionmentioning

confidence: 99%

An Observational Study of the Mesoscale Mistral Dynamics

Guénard

Drobinski

Caccia

et al. 2005

Boundary-Layer Meteorol

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We investigate the mesoscale dynamics of the mistral through the wind profiler observations of the MAP (autumn 1999) and ESCOMPTE (summer 2001) field campaigns. We show that the mistral wind field can dramatically change on a time scale less than 3 hours. Transitions from a deep to a shallow mistral are often observed at any season when the lower layers are stable. The variability, mainly attributed in summer to the mistral/land–sea breeze interactions on a 10-km scale, is highlighted by observations from the wind profiler network set up during ESCOMPTE. The interpretations of the dynamical mistral structure are performed through comparisons with existing basic theories. The linear theory of R. B. Smith [Advances in Geophysics, Vol. 31, 1989, Academic Press, 1–41] and the shallow water theory [Schär, C. and Smith, R. B.: 1993a, J. Atmos. Sci. 50, 1373–1400] give some complementary explanations for the deep-to-shallow transition especially for the MAP mistral event. The wave breaking process induces a low-level jet (LLJ) downstream of the Alps that degenerates into a mountain wake, which in turn provokes the cessation of the mistral downstream of the Alps. Both theories indicate that the flow splits around the Alps and results in a persistent LLJ at the exit of the Rhône valley. The LLJ is strengthened by the channelling effect of the Rhône valley that is more efficient for north-easterly than northerly upstream winds despite the north–south valley axis. Summer moderate and weak mistral episodes are influenced by land–sea breezes and convection over land that induce a very complex interaction that cannot be accurately described by the previous theories

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THE MISTRAL AND FOREST FIRES IN PROVENCE—CÔTE D'AZUR, SOUTHERN FRANCE

Cited by 9 publications

References 4 publications

Characterization of valley flows within two confluent valleys under stable conditions: observations from the KASCADE field experiment

Characterization of valley flows within two confluent valleys under stable conditions: observations from the KASCADE field experiment

Lagrangian dynamics of the mistral during the HyMeX SOP2

An Observational Study of the Mesoscale Mistral Dynamics

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