Aerosols strongly affect the Mediterranean basin located at the crossroads of air masses carrying both natural and anthropogenic particles making the basin an ideal testbed for aerosol effects on climate. The aerosols have strong effects on the regional climate fluctuations from daily to multi-decadal scales due to their direct, semi-direct and indirect effects on radiation, atmospheric circulation and cloud cover. Aerosols also represent one of the main sources of uncertainty in past climate change attribution and future climate change projections at global and regional scales. Due to their relatively short life-time, aerosols influencing the Mediterranean area are mostly produced in nearby regions and therefore they constitute a regional climate forcing of regional origin. In addition, the aerosols show a hig spatio-temporal variability and are influenced by numerous fine-scale processes. The use of high-resolution RCMs therefore fits well to address the four main scientific questions of the proposed FPS:
(1) Can we fully characterize the Mediterranean aerosol past variability and future evolution at climate scales ? in particular using RCMs.
(2) Can we understand the role of the Mediterranean aerosols on the past regional climate variability? including issues related to regional climate change attribution and aerosols representation in climate models (GCM, RCM).
(3) Can we determine the role of regionally-born aerosols in the Mediterranean future climate sensitivity ? in particular using RCMs as complementary approach to GCMs.
(4) What is the aerosol role in shaping the Mediterranean extreme events ? (e.g. heat waves, heavy precipitation events)
The proposed FPS will be facilitated by recent observation efforts such as the ChArMEx programme, long-term multi-variable super-sites, availability of new homogenized datasets for AOD and surface shortwave and longwave radiations from in-situ coordinated networks (AERONET, GEBA, BRSN) and climate-aware satellite initiatives (ESA-CCI).
The representation of aerosols and their effects in RCMs is still very crude and uncertain and a multi-model approach is therefore requested to bring robust answers to the scientific questions CORDEX then constitutes an adequate framework to propose scientifically-based and well-coordinated simulation protocols involving RCMs with various aerosol representations
The proposed FPS targets in particular a better understanding of solar radiation variability and future changes. This is required to anticipate potential energy production or to understand the level of production of existing sites. The FPS may therefore leads to new and innovative climate services for energy producers over the Euro-Mediterranean area. Another outcomes of the FPS concerns the marine biogeochemistry of the oligotrophic Mediterranean Sea ecosystem as particles constitute one of the main sources of regional nutrients.
Besides, this FPS will contribute to several WCRP Grand Challenges, to the CORDEX Challenge about the coupled regional climate models and to the climate modelling activities of the Mediterranean regional programmes of Gewex (HyMeX) and CLIVAR (Med-CLIVAR).
