Mesoscale Influences on Nocturnal Valley Drainage Winds in Western Colorado ValleysSource: Journal of Applied Meteorology:;1992:;volume( 031 ):;issue: 002::page 121DOI: 10.1175/1520-0450(1992)031<0121:MIONVD>2.0.CO;2Publisher: American Meteorological Society
Abstract: The mesoalpha-scale upper-level sounding network data collected during the 1984 ASCOT meteorological and tracer experiments provided a unique opportunity to analyze the nocturnal drainage wind in four different valleys in western Colorado, and to examine the effects of the synoptic-and mesoscale ambient conditions on these valley drainage winds. The six experimental periods, although biased because of a ?fair weather? selection process, provided an additional opportunity to examine ?good? and ?poor? drainage scenarios. The results show that drainage winds fill all four valleys up to 80%?l00% of their valley depths under favorable nocturnal radiative longwave cooling (1.0°?1.5°C h?1) and light (<5 m s?1) ambient winds. Valley drainage, once established, is rather resistant to erosion from above because of the large source regions of these valleys, their large volume fluxes and inertia, and the persistent stable conditions inside these valleys. Wind erosion was observed on three nights when the drainage depth was reduced to less than half of the valley depth. The principal contributing factors to wind erosion processes were above-valley along-valley wind component opposing the drainage, valley stability, height of the 5 m s?1 isotach above the valley, and total above-valley wind acceleration. Generally, wind erosion processes appear to be especially active when above-valley wind speeds exceed 5 m s?1 and accelerations exceed 0.00040 m s?1. Other contributing factors that cause variable or terminated drainage depths are precipitation-evaporation effects causing nonradiative drainage events, wind shear above the valley, cloudiness, frontal passages, and synoptic winds directed in the down-valley direction.
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contributor author | Orgill, Montie M. | |
contributor author | Kincheloe, John D. | |
contributor author | Sutherland, Robert A. | |
date accessioned | 2017-06-09T14:03:48Z | |
date available | 2017-06-09T14:03:48Z | |
date copyright | 1992/02/01 | |
date issued | 1992 | |
identifier issn | 0894-8763 | |
identifier other | ams-11755.pdf | |
identifier uri | http://onlinelibrary.yabesh.ir/handle/yetl/4147018 | |
description abstract | The mesoalpha-scale upper-level sounding network data collected during the 1984 ASCOT meteorological and tracer experiments provided a unique opportunity to analyze the nocturnal drainage wind in four different valleys in western Colorado, and to examine the effects of the synoptic-and mesoscale ambient conditions on these valley drainage winds. The six experimental periods, although biased because of a ?fair weather? selection process, provided an additional opportunity to examine ?good? and ?poor? drainage scenarios. The results show that drainage winds fill all four valleys up to 80%?l00% of their valley depths under favorable nocturnal radiative longwave cooling (1.0°?1.5°C h?1) and light (<5 m s?1) ambient winds. Valley drainage, once established, is rather resistant to erosion from above because of the large source regions of these valleys, their large volume fluxes and inertia, and the persistent stable conditions inside these valleys. Wind erosion was observed on three nights when the drainage depth was reduced to less than half of the valley depth. The principal contributing factors to wind erosion processes were above-valley along-valley wind component opposing the drainage, valley stability, height of the 5 m s?1 isotach above the valley, and total above-valley wind acceleration. Generally, wind erosion processes appear to be especially active when above-valley wind speeds exceed 5 m s?1 and accelerations exceed 0.00040 m s?1. Other contributing factors that cause variable or terminated drainage depths are precipitation-evaporation effects causing nonradiative drainage events, wind shear above the valley, cloudiness, frontal passages, and synoptic winds directed in the down-valley direction. | |
publisher | American Meteorological Society | |
title | Mesoscale Influences on Nocturnal Valley Drainage Winds in Western Colorado Valleys | |
type | Journal Paper | |
journal volume | 31 | |
journal issue | 2 | |
journal title | Journal of Applied Meteorology | |
identifier doi | 10.1175/1520-0450(1992)031<0121:MIONVD>2.0.CO;2 | |
journal fristpage | 121 | |
journal lastpage | 141 | |
tree | Journal of Applied Meteorology:;1992:;volume( 031 ):;issue: 002 | |
contenttype | Fulltext |