The atmospheric moisture budget in the Mediterranean: Mechanisms for seasonal changes in the Last Glacial Maximum and future warming scenario

We have investigated the sensitivity of the Mediterranean atmospheric moisture budget (P-E) to large global mean temperature changes and the mechanisms for its seasonal changes. Model simulations of the Last Glacial Maximum (LGM) and Representative Concentration Pathway rcp8.5 scenario have been compared to pre-Industrial (PI) conditions. We have decomposed (P-E) in thermodynamic, dynamic, transient eddy and surface term. The decomposition revealed that mechanisms for (P-E) changes in the Mediterranean do not follow a simple scaling with temperature from the cold LGM to the warm rcp8.5 and they cannot be described by the thermodynamic contribution associated with the “wet-get-wetter, dry-get-drier” paradigm. Winter changes are caused by the anomalous mean atmospheric circulation. In summer, the thermodynamics provides the largest contribution, but its effect is counteracted by other mechanisms. The Mediterranean response to climate change differs from the averaged behavior of other regions in the same latitudinal belt. The complex spatial interplay of the atmospheric moisture budget contributions results in reduced precipitation in the rcp8.5 and reduced evaporation in the LGM relative to PI. This analysis shows that past (LGM) and future (rcp8.5) atmospheric moisture budget changes have very different basic mechanisms, which cannot be simply linked to changes of global mean temperature