Abstract
Abstract. We present novel measurements from a field campaign that aims to characterize multi-scale flow patterns, ranging from 0.1 to 10 km in a time-resolved manner, in a mountainous region in northwestern Spain with a mountain–valley–ridge configuration. We select two flow cases where topographic-flow interactions were measured by five synchronized scanning Doppler wind lidars along a 10 km transect line that includes a cross section of the valley. We observed a hydraulic jump in the lee side of the mountain. For this case, the Froude number transition from supercritical (>1) at the mountain to subcritical (<1) at the valley is in agreement with previous experiments at a smaller scale. For a 1-year period, the measurements show such a transition about 10 % of the time, indicating a possible high occurrence of hydraulic jumps. The second flow case presents valley winds that are decoupled from the northerly flow aloft and show a stratified layered pattern, which is well captured by the lidar scans and complementary ground-based observations. These measurements can aid the evaluation of multi-scale numerical models as well as improve our knowledge with regards to mountain meteorology.
Highlights
Over flat and homogeneous terrain, such as areas far offshore, the difference between measured and simulated climatological mean wind speeds at wind-energy-relevant heights is in some cases less than 4 % (Olsen et al, 2017)
This paper firstly introduces the Alaiz experiment (ALEX17), which aims to peer into multi-scale flow patterns with mountain–valley interactions
Results show that the New European Wind Atlas (NEWA)-Weather Research and Forecast Model (WRF) simulations underestimate the mean wind by more than 1.5 m s−1, which is indicative of unresolved speed-up effects in the mesoscale model
Summary
Over flat and homogeneous terrain, such as areas far offshore, the difference between measured and simulated climatological mean wind speeds at wind-energy-relevant heights is in some cases less than 4 % (Olsen et al, 2017). Doppler wind lidars and airborne instrumentation have been used to characterize largescale phenomena over steep hills and mountain ranges. Two examples of such are the terrain-induced rotor experiment (T-REX, Grubišicet al., 2008) and the mountain terrain atmospheric modeling and observations program (MATERHORN, Fernando et al, 2015). In parallel to the NEWA project, the second Wind Forecast Improvement Project (WFIP2) deployed a large array of instruments to cover the area around the Columbia River Gorge in the United States (Wilczak et al, 2019) This experiment was focused on the improvement of mesoand microscale coupling methods (Haupt et al, 2019).
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