Thermal asymmetry and cross-valley circulation in a small alpine valley

Hennemuth, Barbara

doi:10.1007/bf00118338

Cited by 25 publications

(22 citation statements)

References 16 publications

(19 reference statements)

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“…Slope flows were observed at the surface stations on the valley sidewalls with speeds around 2 m s −1 as was shown in Section 3.3.1. It is interesting to note that several studies have found a rather inhomogeneous temperature structure across a valley from which the existence of cross-valley circulations could be explained [28,29]. Given the steepness of the Riviera Valley, it may be surprising that horizontal temperature gradients and cross-valley circulations were not clearly seen in the observations.…”

Section: Spatial Structure Of Along-valley Windmentioning

confidence: 92%

The performance of RAMS in representing the convective boundary layer structure in a very steep valley

et al. 2005

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Abstract. Data from a comprehensive field study in the Riviera Valley of Southern Switzerland are used to investigate convective boundary layer structure in a steep valley and to evaluate wind and temperature fields, convective boundary layer height, and surface sensible heat fluxes as predicted by the mesoscale model RAMS. Current parameterizations of surface and boundary layer processes in RAMS, as well as in other mesoscale models, are based on scaling laws strictly valid only for flat topography and uniform land cover. Model evaluation is required to investigate whether this limits the applicability of RAMS in steep, inhomogeneous terrain. One clear-sky day with light synoptic winds is selected from the field study. Observed temperature structure across and along the valley is nearly homogeneous while wind structure is complex with a wind speed maximum on one side of the valley. Upvalley flows are not purely thermally driven and mechanical effects near the valley entrance also affect the wind structure. RAMS captured many of the observed boundary layer characteristics within the steep valley. The wind field, temperature structure, and convective boundary layer height in the valley are qualitatively simulated by RAMS, but the horizontal temperature structure across and along the valley is less homogeneous in the model than in the observations. The model reproduced the observed net radiation, except around sunset and sunrise when RAMS does not take into account the shadows cast by the surrounding topography. The observed sensible heat fluxes fall within the range of simulated values at grid points surrounding the measurement sites. Some of the scatter between observed and simulated turbulent sensible heat fluxes are due to sub-grid scale effects related to local topography.

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Section: Spatial Structure Of Along-valley Windmentioning

confidence: 92%

The performance of RAMS in representing the convective boundary layer structure in a very steep valley

et al. 2005

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“…Because of the small scale at which processes occur, extrapolation of meteorological variables is difficult. A mountain-valley wind (valley breeze) develops for certain periods of the day, and slope winds only exist as long as there are strong temperature gradients between the ground surface and air (Hennemuth 1986). On clear sky days with meta-stable air layering, air temperatures increase by as much as 3…”

Section: Dischma Valley Grisons Switzerlandmentioning

confidence: 99%

Comparison of Evapotranspiration and Condensation Measurements between the Giant Mountains and the Alps

Jong

Mundelius

Migała

2005

Climate and Hydrology in Mountain Areas

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“…Because of the small scale at which processes occur, approximations for extrapolation of weather variables are difficult. A mountain-valley wind (valley breeze) is developed only 2421 for certain periods of the day, and slope winds only exist as long as there are strong temperature gradients between the ground surface and air (Hennemuth, 1986). On clear-sky days with metastable air layering, air temperatures increase at the same pressure level from the valley outlet towards the highest ridges at the valley head (by as much as 3°C) and develop a clear up-valley wind (Ulrich, 1987).…”

Section: Study Areamentioning

confidence: 99%

The contribution of condensation to the water cycle under high‐mountain conditions

Jong

2005

Hydrological Processes

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Abstract:Little is known about the interaction between condensation, precipitation and evaporation as an integral part of the water cycle under high-mountain conditions. This paper focuses on methods of identification and measurement of condensation under natural conditions in high alpine valleys by example of the Dischma in eastern Switzerland. The role of different vegetation zones in transferring water from and to the atmosphere is investigated above the treeline (1900-2600 m a.s.l.). Field measurements of condensation and evaporation at 10 min intervals show that condensation plays a more significant role in the water cycle than previously assumed. Both diurnal and nocturnal condensation are compared at different altitudes on slope and valley locations during the exceptionally hot and dry mid-summer of 1998. It is suggested that, in addition to standard hydrological components, water balance modelling in mountain zones should include more precise data on measured condensation.

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Thermal asymmetry and cross-valley circulation in a small alpine valley

Cited by 25 publications

References 16 publications

The performance of RAMS in representing the convective boundary layer structure in a very steep valley

The performance of RAMS in representing the convective boundary layer structure in a very steep valley

Comparison of Evapotranspiration and Condensation Measurements between the Giant Mountains and the Alps

The contribution of condensation to the water cycle under high‐mountain conditions

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