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James D. Doyle, Qingfang Jiang, Ronald B. Smith, and Vanda Grubišić

(1999) showed that for stratified flow impinging on a topographic ridge, low-level jets occur along the northern and southern portions of the ridge flanks, which they refer to as tip jets. In the Northern Hemisphere, westerly flow is deflected primarily leftward around the obstacle, which results in strong jets and downslope flows along the northern flank. Doyle and Shapiro found that jets along the southern ridge flanks can be prominent as well, and consistent with the principal of conservation of

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Qingfang Jiang and James D. Doyle

-valley soundings are similar to their upstream counterparts except that the 0000 UTC 14 April sounding reveals an approximately 1.5-km-deep westerly jet above the surface. 3) Surface observations The 16 automatic weather stations, each of which consists of a standard 10-m meteorological tower and sensors for wind, temperature, relative humidity, and pressure measurements, were deployed near Independence approximately along three linear segments across the valley floor ( Fig. 1c ). For the convenience of

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Patrick A. Reinecke and Dale Durran

9-km domains are identical. d. Model simulations The 0000 UTC ensemble mean analysis and 0600 UTC ensemble mean forecast of the 500-hPa geopotential height field and wind speeds on the 27-km domain are plotted in Fig. 13 . At the analysis time ( Fig. 13a ) a low pressure trough is located just offshore of the western United States. Associated with the low pressure trough is a jet extending around the base of the trough and into the central portion of California. The wind speeds within the jet

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James D. Doyle, Saša Gaberšek, Qingfang Jiang, Ligia Bernardet, John M. Brown, Andreas Dörnbrack, Elmar Filaus, Vanda Grubišić, Daniel J. Kirshbaum, Oswald Knoth, Steven Koch, Juerg Schmidli, Ivana Stiperski, Simon Vosper, and Shiyuan Zhong

extends from above the mountain to the upstream lateral boundary at an approximate altitude of 5 km. The jet results from an in situ increase in momentum at the upstream boundary that subsequently self-advects toward the ridge. The jet has a minimal impact on the solution by 4 h. Fig . 7. Horizontal perturbation wind component (color, interval 2.5 m s −1 ) and potential temperature (black contours, interval 10 K) for Ex2500_ns ( h m = 2500 m, no slip) at the final time (4 h) for all models and

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Vanda Grubišić and Brian J. Billings

. Weatherwise , 25 , 2 . 56 – 63 . Mitchell , R. M. , R. P. Cechet , P. J. Turner , and C. C. Elsum , 1990 : Observation and interpretation of wave clouds over Macquarie Island. Quart. J. Roy. Meteor. Soc. , 116 , 741 – 752 . Moore , G. W. K. , and I. A. Renfrew , 2005 : Tip jets and barrier winds: A QuikSCAT climatology of high wind speed events around Greenland. J. Climate , 18 , 3713 – 3725 . Pan , F. , and R. B. Smith , 1999 : Gap winds and wakes: SAR observations and

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Christian Kühnlein, Andreas Dörnbrack, and Martin Weissmann

, the gradual change of the wind direction from southwesterlies to northwesterlies can be seen in the sign shift of the meridional wind component during the 12-h period. The upstream upper-level features only change marginally during the period. The wind and θ profiles show a sharp tropopause at 12-km altitude (i.e., a local maximum in N 2 ; see Birner et al. 2002 ), and the jet stream maximum of ≈50 m s −1 underneath that level. The stratospheric θ profiles are characterized by wave

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