## 3 Results
### Comparison of Total ET Estimates and Evaporative Stress Index over AOIs  
Hourly potential evapotranspiration (PET), a derived dataset from the ASCE's standardized reference ET model is used for countrywide atmospheric energy demand comparisons. Zonal statistics were applied to calculate the average precipitation (influx) and PET (outflux) for each country over a year. Figure 4 highlights the hydro-climatic disparities for the year 2019 in the Mediterranean countries. Precipitation is surplus in some countries (e.g., Montenegro, Bosnia, Albania, Italy, and Croatia) and deficits in others. This suggests favorable conditions for water availability, agriculture, and ecosystems in some southeast Mediterranean countries with precipitation surpluses. In contrast, the majority of Middle Eastern and North African (MENA) countries received less than 500 mm of annual rainfall, with the exceptions of Lebanon and Cyprus. Notably, Egypt is one of the driest countries, where PET reached above 1500 mm. In Egypt and other MENA countries (Libya, Tunisia, Algeria, Morocco) rainfall is low but evaporation demand is high, and agriculture is irrigation dependent. This makes water demand a dominant factor controlling water availability in the region. However, irrigation supplements the water deficit and allows agricultural activities to persist. The dependence on irrigation systems also highlights these regions' fragility to changes in climate variability. Strong climate variability over southern Europe, Turkey, and the western Balkans has also been observed in recent years, affecting the water budget, and making their land use systems more vulnerable to water stress, which makes the two distinct climate clusters of hydrological imbalances more intense [4], as shown in Figure 4 with a dotted borderline. The comparison of ET across different land cover types of seven AOIs reveals more distinct model behaviors in arid regions. Figure 5a presents the area-averaged annual ET sums from all models across seven AOIs, in which SCOPE exhibits the highest values over croplands in Turkey, Morocco, Egypt, and the grasslands of Spain. In these areas with high PET near 1500 mm, indicating a high atmospheric water demand, GLEAM and TerraClimate show considerably lower ET there compared to other models, indicating their limitation in the arid cultivated regions. These model discrepancies highlight the importance of not relying on a single ET product for water use assessment. A complementary approach using multiple ET datasets is recommended for the arid regions in the Middle East and North Africa (MENA). However, differences in case of France, Italy, and the Balkans are less pronounced. Here, TSEB shows relatively low ET estimates over the forest ecosystems. Figure 4: The figure shows aggregated precipitation and potential ET in the year 2019 over different Mediterranean countries, retrieved from the annual total Precipitation from Soil Moisture to Rain (SM2 rain) and Potential ET (PET) product from ERA5. Figure 5: _Cont_. The Evaporative Stress Index (ESI) is employed to further assess how different ET products can influence the assessment of water stress (Figure 5b). An ESI value of \(-1.5\) or lower indicates severe water stress, while +1.5 or higher suggests excessive soil moisture [49]. By comparing ESI derived from different models' ET outputs, we observed variations in model performance over AOIs. For example, over croplands in Egypt, STEPS-GLEAM indicated water stress in June and July, whereas SCOPE-TSEB indicated earlier stress in May. It shows their effectiveness for irrigated croplands, assessing water demand earlier. Over grasslands in Spain, TSEB, MOD16A2, GLEAM, and TerraClimate showed a summer deficit, while STEPS and SCOPE did not, showing usability of the former over Spain. In the Balkan Forest, all models behaved entirely differently, making it challenging to decipher the uniform ET pattern of this region. The response of models over croplands in France was more consistent.