## 3 Results  
### Spatial-Temporal Variations of Ecosystems' AET, GPP, and WUE  
The spatial distribution of AET values varied significantly in the terrestrial ecosystems of the Middle East between 1982 and 2017 (Figure 3a). This variance is explained by several climatic and hydrological conditioning factors. In this regard, the regional spatial annual mean of AET values was 220 mm yr\({}^{-1}\). In general, the spatial distribution of the values of AET reached its highest values (\(<\)400 mm yr\({}^{-1}\)) in the north and northwest of the area under study, especially in northern Iran and Turkey and some western parts of Syria and Lebanon. Moreover, these areas are subject to the Mediterranean climate in a mountainous environment, implying a high-intensity orographic rainfall pattern (annual precipitation \(<\) 1000 mm), thereby implying high water abundance, high humidity, and relatively short drought episodes. The AET value was the lowest (\(<\)400 mm yr\({}^{-1}\)) in the central, south, and east of the area under study, especially in most of the territories in Iran, Iraq, Syria, Jordan, and Palestine.  
The regional annual mean of GPP values was 277 g C m\({}^{2}\) yr\({}^{-1}\). Most of the territories in central Iran, Iraq, Syria, and Jordan (Figure 3b) recorded the lowest values of GPP (\(<\)400 g C m\({}^{2}\) yr\({}^{-1}\)); these regions showed a negative trend (\(-\)0.3 to \(-\)5 g C m\({}^{2}\) per decade) in contrast to that in the far northern west Iran, and most of the Turkish and Lebanese territories have positive significant trends (\(+\)15 to \(+\)45 g C m\({}^{2}\) per decade) (Figure 3d,e). Referring to the spatial distribution of WUE values, all countries under study were characterized by a noticeable spatial variation in the distribution of WUE values with a multiyear average of 1.1 g C mm\({}^{-1}\) yr\({}^{-1}\). For instance, WUE values of \(<\)2 g C mm\({}^{-1}\) yr\({}^{-1}\) dominated most of the ecosystem territories of the study area (Figure 3c). In marked contrast, the whole ecosystem territories of Lebanon, western Syria, Palestine, northern Turkey, Iran, and southern Jordan were subjected to WUE values of \(>\)2 g C mm\({}^{-1}\) yr\({}^{-1}\). Figure A1 in Appendix A shows the spatial-temporal distribution of the WUE values in detail. WUE values of \(<\)0.2 g C mm\({}^{-1}\) yr\({}^{-1}\) dominated most of the area under study in 1994, while most  
Figure 2: A scheme to illustrate the DS across time and extract multiyear drought events.  
of the area achieved WUE values of >1 g C mm\({}^{-1}\) yr\({}^{-1}\) in 1984. It is worth noting that WUE trends are consistent with those of GPP (Figure 3f,g).  
Figure 4 shows the quantitative variation of the ecosystems' values of AET, GPP, and WUE for each land cover type and prevailing climate patterns. TCA cover achieved the highest values of AET, GPP, and WUE with values of 440 mm yr\({}^{-1}\), 791 g C m\({}^{-2}\) yr\({}^{-1}\), and 1.82 g C mm\({}^{-1}\) yr\({}^{-1}\), respectively, while bare soil produced the lowest AET and GPP values, with 156 mm yr\({}^{-1}\) and 87 g C m\({}^{-2}\) yr\({}^{-1}\), respectively. Sparse vegetation cover, however, produced the lowest values of WUE (0.78 g C mm\({}^{-1}\) yr\({}^{-1}\)). Regarding the climatic pattern, the Cfa pattern showed the highest values of AET (628 mm yr\({}^{-1}\)) and GPP (1512 g C m\({}^{-2}\) yr\({}^{-1}\)), whilst the Cfb pattern produced the greatest values of WUE (2.43 g C mm\({}^{-1}\) yr\({}^{-1}\)). In contrast, the Bsh climate type produced the lowest WUE with a value of 0.7 g C mm\({}^{-1}\) yr\({}^{-1}\).  
Figure 3: **(a–c)** Multiyear average of ecosystems’ AET, GPP, and WUE over Western Asia between 1982 and 2017. **(d–g)** Temporal trends of annual GPP and WUE (changes per decade and significant upwards and downwards trends). sP: significant positive, sN.: significant negative, and ins.: insignificant.