Assessing the suitability of global evapotranspiration products over irrigated areas

Abstract. Reliable estimation of evapotranspiration (ET) over irrigated croplands is crucial for agricultural water management, hydrological modeling, and monitoring of land–atmosphere exchanges. Yet the reliability of global ET datasets in these environments remains insufficiently assessed. Here, we evaluate six widely used global ET products (FLUXCOM RS, GLEAM v4.2a, PMLv2, ERA5-Land, MOD16A2, and SSEBop v6.1), covering a wide range of modeling approaches, to assess their ability to capture irrigation-related ET signals. The assessment combines spatial and seasonal evaluations across diverse agro-climatic regions, using three complementary references: a map of area equipped for irrigation, the OpenET ensemble, and eddy covariance measurements from irrigated croplands. Results reveal strong contrasts in how well the products reproduce reference patterns. PMLv2, SSEBop v6.1, and FLUXCOM RS show the highest agreement, effectively capturing irrigation-related spatial and seasonal ET variations. MOD16A2 shows moderate agreement, with consistently lower ET values than the reference datasets. ERA5-Land and GLEAM v4.2a exhibit the weakest correspondence, reflecting limitations linked to their precipitation-driven water-balance soil moisture and stress formulations. Differences among products mainly reflect how water stress is represented and whether irrigation-sensitive variables such as land surface temperature and vegetation properties are incorporated. This multi-scale evaluation provides guidance for selecting ET products in irrigated regions and highlights priorities for improving the representation of irrigation in global ET models.