Along-Valley Structure of Daytime Thermally Driven Flows in the Wipp Valley

Rucker, Magdalena; Banta, Robert M.; Steyn, D. G.

doi:10.1175/2007jamc1319.1

Cited by 25 publications

(19 citation statements)

References 35 publications

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“…An acceleration of the along-valley flow has been observed in other valleys (e.g., Rucker et al 2008;Whiteman 2000). Such an acceleration is counterintuitive because one might expect a loss of valley airmass through the tributary valleys and side canyons (Zardi and Whiteman 2012).…”

Section: ) Spatial Wind Structure In the Salinas Valleymentioning

confidence: 97%

“…For example, in the case of an adjacent ocean, sea breezes can interact with valley flows to generate an extended sea breeze (e.g., Kondo 1990). In addition, synoptic flows can be subject to channeling into valleys (Whiteman 2000), and upvalley flows have been observed to accelerate along the valley floor (Rucker et al 2008). Across the valley, flow heterogeneities have been observed that result from dynamical effects caused by bends in the valley (De Wekker et al 2005;Weigel et al 2006) and thermally driven cross-valley circulations (Bader and Whiteman 1989).…”

Section: Introductionmentioning

confidence: 99%

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Airborne Doppler Lidar Measurements of Valley Flows in Complex Coastal Terrain

Wekker

Godwin

Emmitt

et al. 2012

Journal of Applied Meteorology and Climatology

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Three-dimensional winds obtained with an airborne Doppler lidar are used to investigate the spatial structure of topographically driven flows in complex coastal terrain in Southern California. The airborne Doppler lidar collected four hours of data between the surface and 3000 m MSL along a 40-km segment of the Salinas Valley during the afternoon of 12 November 2007. The airborne lidar measurements, obtained at horizontal and vertical resolutions of approximately 1500 and 50 m, respectively, reveal a detailed spatial structure of the atmospheric flows within the valley and their associated aerosol features. Clear skies prevailed on the flight day with northwesterly synoptic flows around 10 m s 21 . The data document a shallow sea breeze making a transition into an upvalley flow in the Salinas Valley that accelerates in the upvalley direction. Along with the acceleration of the upvalley wind, the lidar data indicate the presence of enhanced sinking motions. No return flows associated with the sea-breeze or upvalley flows are observed. While synoptic flows are aligned along the valley axis in the upvalley direction, lidar data indicate the presence of a northerly crossvalley flow around the height of the surrounding ridges. This flow intrudes into the valley atmosphere and induces, along with thermally driven slope flows on the sunlit valley sidewall, a cross-valley circulation that causes an asymmetric distribution of the aerosols. This study demonstrates the large potential of airborne Doppler lidar data in describing flows in complex terrain.

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Section: ) Spatial Wind Structure In the Salinas Valleymentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Airborne Doppler Lidar Measurements of Valley Flows in Complex Coastal Terrain

Wekker

Godwin

Emmitt

et al. 2012

Journal of Applied Meteorology and Climatology

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“…Groundbased remote sensing systems, such as Doppler lidars, have proved extremely useful for the description of the kinematic structure of cold fronts over complex terrain (Darby, et al, 1999;Neiman, et al, 2001;Darby and Poulos, 2006). During the MAP SOP such a Doppler lidar had been operated in the Wipp Valley to investigate south foehn (Flamant, et al, 2002;Durran, et al, 2003;Weissmann, et al, 2004;Zängl and Gohm, 2006;Marić and Durran, 2009) as well as thermally driven flows (Rucker, et al, 2008). In our cold front study we will use data from the same lidar.…”

Section: Introductionmentioning

confidence: 99%

Evolution and structure of a cold front in an Alpine valley as revealed by a Doppler lidar

Gohm

Mayr

Darby

et al. 2010

Q.J.R. Meteorol. Soc.

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“…These studies described a wind reversal twice per day at the slope and valley scale in response to local density gradients under fair-weather conditions. Eighty years later, these concepts remain central but it is known now that the local dynamics strongly depend on orographic arrangement and the literature shows that this cannot be generalized from one valley to another (Rucker et al, 2008;Duine et al, 2017;Giovannini et al, 2017). These local dynamics show a seasonal variability with solar forcing driving the relative period of daytime and night-time regimes (Bader and Whiteman, 1989;Whiteman, 2000;Zängl, 2004).…”

Section: Introductionmentioning

confidence: 99%

Semi‐idealized simulations of wintertime flows and pollutant transport in an Alpine valley: Origins of local circulations (Part I)

Sabatier

Paci

Lac

et al. 2020

Quart J Royal Meteoro Soc

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Mountainous terrains are known for driving their own dynamics which respond to the local morphological arrangement of the area. Thermally driven flows in particular develop at slope and valley scales and ensure a certain degree of pollutant dispersion under quiescent wintertime synoptic conditions. The present study focuses on a section of the Arve River valley situated close to Mont Blanc which frequently suffers from severe pollution episodes under stable wintertime conditions whilst surrounding valleys appear to be less affected. The particular shape of this basin‐like section and its location at the confluence of several tributary valleys raises the question of the extent to which local circulations participate in pollutant trapping over restricted sectors. A set of high‐resolution numerical simulations are designed in order to improve our understanding of the local flow structure and their sensitivity to thermal stratification, radiative forcing and snow cover. The tributary valleys play a major role in both daytime and night‐time dynamics by deflecting the entering daytime flux and constraining the night‐time flow trajectories. In addition, the basin morphology greatly influences the circulations. During daytime a two‐layer wind structure is developed and driven by spatial variations in sun exposure which is particularly heterogeneous under wintertime forcing. Early spring radiative forcing or the presence of snow allow both of them to develop more homogeneous circulations through the reduction of sun exposure variations, except when snow cover is restricted to shaded basin sidewalls. At night, a three‐layer wind structure is developed. It favours air mass ventilation in the western linear branch of the basin whilst stagnation and recirculation prevail in the curved part of the valley which is also the most polluted. This study therefore highlights spatial variations in circulation patterns consistent with the accumulation of observed pollutants and their heterogeneous distribution.

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Along-Valley Structure of Daytime Thermally Driven Flows in the Wipp Valley

Cited by 25 publications

References 35 publications

Airborne Doppler Lidar Measurements of Valley Flows in Complex Coastal Terrain

Airborne Doppler Lidar Measurements of Valley Flows in Complex Coastal Terrain

Evolution and structure of a cold front in an Alpine valley as revealed by a Doppler lidar

Semi‐idealized simulations of wintertime flows and pollutant transport in an Alpine valley: Origins of local circulations (Part I)

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