The Alaiz experiment: untangling multi-scale stratified flows over complex terrain
Pedro Santos, Jakob Mann, Nikola Vasiljević, Elena Cantero, Javier Sanz Rodrigo, Fernando Borbón, Daniel Martínez‐Villagrasa, Belén Martí, Joan Cuxart
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.