Influence of lee waves and rotors on the near‐surface flow and pressure fields in the northern foreland of the Tatra Mountains

This study presents the results of a field campaign aimed at observing near‐surface flow and pressure fields downwind of the Tatra Mountains. The general objective was to study low‐level turbulence associated with lee waves and rotors and to improve weather forecasts for aviation. The main instrumentation consisted of a network of nine weather stations arranged as a transect perpendicular to the Tatra Mountains. The stations recorded the wind speed and direction (at 10 m), atmospheric pressure, temperature and humidity (at 2 m) for ∼2 years. Gliding flights and cloud cover observations using two digital sky cameras also formed part of the campaign. The measurements were supported by data from atmospheric soundings in Poprad (Slovakia) and satellite images provided by the Moderate Resolution Imaging Spectroradiometer ( MODIS ). During a stable southerly flow, episodes of flow separation were observed, which are associated with lee‐wave and rotor activity aloft. Based on data from the selected period, surface‐pressure perturbations arranged as alternate positive and negative anomalies with extreme values of up to ∼0.7 hPa were detected. Positive (negative) anomalies are assumed to be a response of the surface‐pressure field under the influence of descending (ascending) wave or rotor currents because of the downward (upward) component of the air movement in the atmosphere. The relationship between the decreasing magnitudes of the pressure perturbations with the distance from the Tatra Mountains was exposed. It was also possible to demonstrate the dependence of the position and intensity of pressure anomalies in relation to changes in wind conditions.