Lidar observations of low-level wind reversals over the Gulf of Lion and characterization of their impact on the water vapour variability
Di Girolamo, Paolo ; Flamant, Cyrille ; Cacciani, Marco ; Summa, Donato ; Stelitano, Dario ; Richard, Evelyne ; Ducrocq, Véronique ; Fourrié, Nadia ; Said, Frédérique ; Davies, Roger ; Egli, Luca ; Schmutz, Werner
Water vapour measurements from a ground-based Raman lidar and an airborne differential absorption lidar, complemented by high resolution numerical simulations from two mesoscale models (Arome-WMED and MESO-NH), are considered to investigate transition events from Mistral/Tramontane to southerly marine flow taking place over the Gulf of Lion in Southern France in the time frame September-October 2012, during the Hydrological Cycle in the Mediterranean Experiment (HyMeX) Special Observation Period 1 (SOP1). Low-level wind reversals associated with these transitions are found to have a strong impact on water vapour transport, leading to a large variability of the water vapour vertical and horizontal distribution. The high spatial and temporal resolution of the lidar data allow to monitor the time evolution of the three-dimensional water vapour field during these transitions from predominantly northerly Mistral/Tramontane flow to a predominantly southerly flow, allowing to identify the quite sharp separation between these flows, which is also quite well captured by the mesoscale models.
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