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| Titel |
High-resolution observations of the near-surface wind field over an isolated mountain and in a steep river canyon |
| VerfasserIn |
B. W. Butler, N. S. Wagenbrenner, J. M. Forthofer, B. K. Lamb, K. S. Shannon, D. Finn, R. M. Eckman, K. Clawson, L. Bradshaw, P. Sopko, S. Beard, D. Jimenez, C. Wold, M. Vosburgh |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 7 ; Nr. 15, no. 7 (2015-04-08), S.3785-3801 |
| Datensatznummer |
250119619
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| Publikation (Nr.) |
 copernicus.org/acp-15-3785-2015.pdf |
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| Zusammenfassung |
| A number of numerical wind flow models have been developed for simulating
wind flow at relatively fine spatial resolutions (e.g., ~ 100 m);
however, there are very limited observational data available for evaluating
these high-resolution models. This study presents high-resolution surface
wind data sets collected from an isolated mountain and a steep river canyon.
The wind data are presented in terms of four flow regimes: upslope,
afternoon, downslope, and a synoptically driven regime. There were notable
differences in the data collected from the two terrain types. For example,
wind speeds on the isolated mountain increased with distance upslope during
upslope flow, but generally decreased with distance upslope at the river
canyon site during upslope flow. In a downslope flow, wind speed did not have
a consistent trend with position on the isolated mountain, but generally
increased with distance upslope at the river canyon site. The highest
measured speeds occurred during the passage of frontal systems on the
isolated mountain. Mountaintop winds were often twice as high as wind speeds
measured on the surrounding plain. The highest speeds measured in the river
canyon occurred during late morning hours and were from easterly down-canyon
flows, presumably associated with surface pressure gradients induced by
formation of a regional thermal trough to the west and high pressure to the
east. Under periods of weak synoptic forcing, surface winds tended to be
decoupled from large-scale flows, and under periods of strong synoptic
forcing, variability in surface winds was sufficiently large due to
terrain-induced mechanical effects (speed-up over ridges and decreased speeds
on leeward sides of terrain obstacles) that a large-scale mean flow would not
be representative of surface winds at most locations on or within the terrain
feature. These findings suggest that traditional operational weather model
(i.e., with numerical grid resolutions of around 4 km or larger) wind
predictions are not likely to be good predictors of local near-surface winds
on sub-grid scales in complex terrain. Measurement data can be found at
http://www.firemodels.org/index.php/windninja-introduction/windninja-publications. |
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