Water vapour mixing ratio distribution in the area of Naples by Raman lidar measurements and a high resolution model

During August-October 2005, several lidar measurements have been performed at many Italian lidar stations during the Launch (International Lindenberg campaign for Assessment of hUmidity aNd Cloud profiling systems and its impact on High-resolution modelling) campaign according with the IOP (Intensive Operational Period) schedule. IOP 4 episode (1-3 October 2005) has been selected and investigated with a special attention to the variability of water vapour mixing ratio vertical distribution to better understand the associated circulation in the coastal waters of the Gulf of Naples (Tyrrhenian Sea). A simulation is performed using the mesoscale model MM5 (version 3) model from PSU/NCAR1,2 for this study. Water vapour mixing ratio observations have been detected in the Naples site (40°50'N, 14°11'E, 118 m asl) by a water vapour Raman lidar which is also able to measure the backscatter profile at 355 and 532 nm and the extinction profile at 355 nm. Water vapour mixing ratio vertical profiles retrieved by lidar have been compared with the MM5 water vapour mixing ratio vertical profiles. The agreement between the model and the lidar data is good; all the modelled and the lidar profiles are able to capture the cold air intrusion, that is the sharp decrease of the water vapour mixing ratio at about 2000 m. Also the water-layer between 3000 and 8000 m is well captured. Moreover, both the model and the observations are able to capture the land/sea breeze phenomena.