The thermal structure of the inn valley atmosphere

Nickus, Ulrike; Vergeiner, I.

doi:10.1007/bf02257725

Cited by 26 publications

(18 citation statements)

References 3 publications

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“…Urfer (1967) reports that the upslope winds start 2-37 min after local sunrise; considering a retardation of the pressure difference of several minutes we also obtain a reaction time of a few minutes. Calculation of the reaction time l/k for the valley wind from @/ax and u produces a value of 30 min, which is in agreement with Nickus and Vergeiner (1984).…”

Section: Explanation Of the Wind Field In The Dischma Valleysupporting

confidence: 71%

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

Hennemuth¹

1986

Boundary-Layer Meteorol

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Wind observations from a small Alpine valley are used to investigate the problem of cross-valley winds. The observed daytime windfield is a superposition of dynamically and thermally forced cross-winds. Prevailing cross-winds above the valley result in a recirculation cell above the lee slope. The return flow is strengthened or weakened by thermal effects which induce a wind that blows from the shaded to the sunny side of the valley. The reaction time of the thermally induced cross-winds is only 4 min. The horizontal and vertical motions of the cross-valley circulation transport heat in such a way that the insolation differences between the two sides of the valley are nearly equalized.

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Section: Explanation Of the Wind Field In The Dischma Valleysupporting

confidence: 71%

“…The question of reaction time of the cross-valley wind system to the thermal asymmetry may be treated with the equation which includes the pressure forcing (compare Nickus and Vergeiner, 1984). k is determined from the regression of &/dv and u for each grid point in the cross-section.…”

Section: Explanation Of the Wind Field In The Dischma Valleymentioning

confidence: 99%

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

Hennemuth¹

1986

Boundary-Layer Meteorol

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“…Normally, it takes about six hours before an approximately steady state is reached [119]. The surface wind itself reacts to changes of the pressure gradient on a timescale of 30-45 min [118,120,121].…”

Section: Valley Windsmentioning

confidence: 99%

Exchange Processes in the Atmospheric Boundary Layer Over Mountainous Terrain

et al. 2018

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Abstract:The exchange of heat, momentum, and mass in the atmosphere over mountainous terrain is controlled by synoptic-scale dynamics, thermally driven mesoscale circulations, and turbulence. This article reviews the key challenges relevant to the understanding of exchange processes in the mountain boundary layer and outlines possible research priorities for the future. The review describes the limitations of the experimental study of turbulent exchange over complex terrain, the impact of slope and valley breezes on the structure of the convective boundary layer, and the role of intermittent mixing and wave-turbulence interaction in the stable boundary layer. The interplay between exchange processes at different spatial scales is discussed in depth, emphasizing the role of elevated and ground-based stable layers in controlling multi-scale interactions in the atmosphere over and near mountains. Implications of the current understanding of exchange processes over mountains towards the improvement of numerical weather prediction and climate models are discussed, considering in particular the representation of surface boundary conditions, the parameterization of sub-grid-scale exchange, and the development of stochastic perturbation schemes.

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“…Based on the studies of wind regimes in the Inn Valley in Austria, by Nickus and Vergeiner (1984) and Vergeiner and Dreiseitl (1987), an estimate of the response time of valley winds to pressure gradient forcing can be obtained using the following simplified equation of motion for the along-valley wind component:…”

Section: Mesoscale Thermal Forcing and Wind Speed Oscillationsmentioning

confidence: 99%

Diurnal Evolution of Three-Dimensional Wind and Temperature Structure in California's Central Valley

Zhong

Whiteman

Bian³

2004

Journal of Applied Meteorology

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The diurnal evolution of the three-dimensional summer-season mean wind and temperature structure in California's Sacramento and San Joaquin Valleys (collectively called the Central Valley) is investigated using data from 22 radar wind profiler/radio acoustic sounding systems (RASS) operated as part of the Central California Ozone Study in 2000. The profiler network revealed, for the first time, that the persistent summer-season flow pattern documented by surface observations extends 800-1000 m above the surface. At most locations, upvalley winds persist during both day and night except at the upper ends of the valleys and close to the valley sidewalls where diurnal wind reversals occur. Wind speeds exhibit pronounced diurnal oscillations, with amplitudes decreasing with height. A low-level wind maximum occurs in the lowest 300 m, with a sharp decrease in speed above the maximum. Especially well defined nocturnal low-level jets occur at sites in the southern San Joaquin Valley, where maximum speeds of 10 m s Ϫ1 or more occur 1-2 h before midnight at heights near 300 m. The afternoon mixed layer, generally deeper than 1000 m, increases in depth with up-valley distance in both valleys. At night, temperature inversions develop in the lowest several hundred meters with near-isothermal layers above. Mean temperatures in the lowest 500 m of the valleys are always warmer than at the same altitude over the coast, and temperature increases from the lower to upper valleys. The diurnal oscillations of the coastvalley and along-valley temperature and pressure difference reach a maximum in late afternoon and a minimum in early morning. These oscillations are in phase with the diurnal variation of westerly onshore flows. The alongvalley wind maxima, however, occur 1-2 h before midnight, whereas the along-valley pressure gradient maxima are usually found just before sunset.

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The thermal structure of the inn valley atmosphere

Cited by 26 publications

References 3 publications

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

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

Exchange Processes in the Atmospheric Boundary Layer Over Mountainous Terrain

Diurnal Evolution of Three-Dimensional Wind and Temperature Structure in California's Central Valley

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