Background and scope

Water availability is one of the main limitations in the Mediterranean region given the characteristic severe dryness recorded in the warm season and as consequence of the strong interannual variability of precipitation, which causes severe and long-lasting droughts with noticeable hydrological, ecological and socioeconomic impacts. Moreover, total precipitation is characterised to concentrate in very few days in some Mediterranean regions, generating not only long dry spells but high rainfalls that commonly cause flash floods with devastating personal and economic consequences.
If we would try to synthetize the main challenges associated to the climate in the Mediterranean region, probably the precipitation would be in one of the first positions given the several implications associated to its excess or deficit and the strong spatial and temporal complexity characteristic of the precipitation in the region. The research topics in which precipitation is involved are very diverse. Currently, although there are still important gaps in the availability of precipitation data in some areas of the Mediterranean region, we know very well what is the average spatial distribution of precipitation over the region. Nevertheless, there are important uncertainties related to the long-term precipitation evolution, with a current scientific debate on the Mediterranean precipitation dynamic associated to the anthropogenic forcing or to the natural climate variability. Moreover, if there are gaps in the determination of the evolution of precipitation at the annual, seasonal and monthly time scales, our understanding of the precipitation dynamic diminishes in agreement with the frequency of the precipitation observations, so the evolution of daily and sub-daily scales shows important uncertainties that are necessary to solve with more available observations that may represent more regions and time periods.

Challenges

Current challenges are related to the better knowledge of the precipitation dynamic in the Mediterranean and to a variety of topics:

• understanding the complex dynamic and thermodynamic mechanisms that determine the variability of precipitation at different spatial scales and temporal frequencies, with important implications for the short-term and the seasonal forecasting,
• knowing the mechanisms, characteristics and dynamic of the anomalous precipitation conditions, which cause extreme events like floods and droughts,
• assessing the goodness of the precipitation projections under scenarios characterised by high greenhouse gasses emissions, considering the need of high spatial resolution assessment given the complex of the relief and the atmospheric influences, etc.

Meetings and activities

• UNESCO workshop on Mediterranean precipitation changes (Montpellier 22-24 November 2022)

The Precipitation WG has started reinforcing the cooperation between the different Mediterranean countries in order to advance in the data sharing necessary to determine with robustness the long-term dynamic of precipitation at the annual and seasonal scales. For this purpose a UNESCO workshop on Mediterranean precipitation changes was celebrated in Montpellier 22-24 November 2022 in which 28 scientists and members of national meteorological institutes of the majority of the Mediterranean countries attended the meeting in which it was agreed to advance in the development of a database that allows the study related to the long-term precipitation trends considering the whole available precipitation data available. In the coming months it is expected to organise some particular scientific activities related to the Mediterranean precipitation from a wide perspective (special sessions in scientific conferences, e.g., EGU) and more focused meetings on particular precipitation topics.