2) Dr. Rafat Qubaja

Evapotranspiration (ET) has historically been the most uncertain component of the hydrological cycle. Remote sensing of water fluxes has advanced substantially in recent decades. In 2018, NASA launched the ECOSTRESS mission with a primary focus on obtaining high resolution (70-m) with a primary focus on ET and its components. We conducted the first comprehensive evaluation of ECOSTRESS products against in situ arid ecosystems and global weather stations over three years. On average, ECOSTRESS overestimated ET by twofold at site-, ecosystem- and dryland scales, and by 20% at the global scale. A detailed analysis of in situ data revealed the sources of this mismatch in the functions that reduce potential to actual ET and partition ET into its components. We provide new parameters for these functions that greatly improve the accuracy of the ECOSTRESS ET product at site, regional, and global scales. Estimated global precipitation and ET through 2019–2022 are 788 ± 19 and 586 ± 5 mm/year, respectively. Globally, the relative contribution of transpiration and evaporation are 0.42, and 0.58, respectively. Global driver of ET and Its partitioning is largely related to leaf area index (LAI), while precipitation (P) and atmospheric evaporative demand (VPD) have secondary roles. Our study is the first large-scale evaluation and global scaling of ECOSTRESS, including extensive validation in dryland ecosystems and the first ground-truthed assessment of ET components. These, together with the new advances of ECOSTRESS, provide a substantial advance in the utility of ECOSTRESS to provide the most robust ecosystem, regional, and global estimates of ET and its components to date.