The vertical distribution of Saharan dust over the western and central Mediterranean through dust modelling and lidar observations

摘要

Aerosol extinction vertical profiles during Saharan dust events measured by two EARLINET lidar stations in the western and central Mediterranean during a two-year period (2001-2002) are compared to profiles forecasted by the Dust Regional Atmospheric Model (DREAM) that currently operates dust forecasts over the Mediterranean region. 35 Saharan dust cases were successfully captured in Barcelona (Spain) with a 1064 nm backscatter lidar and 45 Saharan dust cases in Naples (Italy) with a 351 nm Raman lidar. The objective of the present study is twofold: (1) to evaluate the skills of the model to forecast the dust vertical distribution in the Mediterranean basin and (2) to study the synoptic pattern dependence of the Saharan dust events over the western and central Mediterranean. The comparison between the modeled and the measured mean annual aerosol extinction vertical profiles shows a rather good agreement between model forecasts and lidar data. However, below 2000 m the extinction measured by the lidar systems is not captured by DREAM due to the significant influence of local anthropogenic aerosols in the boundary layer. The main synoptic patterns responsible for all the measured events of Saharan dust were identified and classified for both sites. It was found that the main synoptic situations in which the Saharan dust reaches the Mediterranean basin are anticyclonic systems located in North Africa (both for dust transport over the western and the central Mediterranean) and a low pressure system located in Portugal (for the western Mediterranean) and in Central Europe (for the central Mediterranean). In the presence of low pressure, the altitude of the dust plume is higher in the western than in the central Mediterranean and this is probably related to geographical factors.