One of the largest challenges facing environmental science is understanding future changes in the terrestrial water cycle and the subsequent impact on water resources. It has also been recognized by international organizations such as the World Climate Research Programme (WCRP) that human activities are playing a key role in modifying the continental water cycle, and therefore must be accounted for in projections. As highlighted by the WCRP Grand Challenge on "Water for the Food Baskets of the World", this issue is especially critical in bread basket regions where water resources are already limited, such as the Mediterranean basin. Climate projections from the Coupled Model Intercomparison Project phase 5 (CMIP5) predict that the Mediterranean region will be a so-called climate change "hot spot" during the twenty-first century. Understanding the processes that drive the hydrological cycle in this region is a key aim of the international HYdrological cycle in the Mediterranean Experiment (HyMeX).

      Semi-arid regions are also hot spots for biases in climate model variables, in particular land surface temperature (LST) and components of the surface energy balance. The Mediterranean basin is also characterized by highly heterogeneous land cover in terms of both natural and anthropized surfaces. Since rainfall is essentially limited to winter and mountainous areas, human management of the natural river systems is required to provide water for crops and an ever-increasing population. Dams and extraction for irrigation modify the amount and timing of the water flowing into the ocean. Irrigation is also known to significantly impact local atmospheric boundary layer (ABL) growth and structure, in addition to modifying near surface atmospheric conditions and increasing convective activity and clouds downwind of irrigated areas. The understanding of the impact of anthropization and its representation in models have been inhibited due to a lack of consistent and extensive observations. Here we present the plans for the international LIAISE project, under the auspices of HyMeX, which will bring together ground-based and airborne measurements with modeling studies including data assimilation of remotely-sensed data to improve our understanding of key natural and anthropogenic land processes and the subsequent feedbacks with the Mediterranean boundary layer and basin-scale hydrological cycle.

We would like to thank Antoni Térmens for the design of the LIAISE logo.