Surface pressure disturbance in the Ebro Valley (Spain) produced by the Pyrenees mountains during PYREX
Résumé
In this paper, the pressure anomaly created by the Pyrenees during the Pyrenees Experiment (PYREX) in the Ebro Valley is studied and analysed. In the first part, pressure disturbance is obtained during some selected cases of PYREX by subtracting the synoptic component from the pressure registered by microbarographs and regular meteorological stations located in the area. As expected from a linear model, a low pressure is found for northerly synoptic winds and a high pressure for southerly synoptic winds. Data shows that the maximum pressure anomaly observed may reach values of the order of 7 hPa. Pressure-anomaly spatial patterns found inside the valley are classified by using principal component analysis (PCA). It is found that the first axes deduced from the PCA carried out represent 75% of the variance in pressure data, indicating that all the stations analysed observed pressure anomalies in a correlated manner. Pressure anomalies are then related to incident-air characteristics expressed as Froude and Rossby numbers. Significant correlation is generally found with these numbers in all cases, demonstrating the dynamic origin of the pressure anomaly computed.
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