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Abstract

The objective of this study is to validate actual evapotranspiration (Aet) simulation (1982 – 2011) over three agro-climatic regions (Sahel, Savannah, and Guinea) within Nigeria. For this investigation, the mesoscale hydrologic model (mHM) was calibrated for streamflow simulation using CHIRPS and ERA5 rainfall datasets in three basins (Jamaare, Hadejia, and Kaduna) in Nigeria. Model parameter sets obtained from these simulations were each used to set up mHM for Aet simulation over Nigeria and the three regions. Model results were compared against estimates from Aet-based products (GLEAM3.5a and FLUXNET). deseasonalized monthly Aet time series plots for all agro-climatic regions and the whole Nigeria domain in comparison to both gridded datasets (GLEAM3.5a and FLUXNET) gave satisfactory correlation scores, especially with the GLEAM3.5a. In the Savannah region, all parameter sets gave satisfactory correlation values (r > 0.5) except that from the Kaduna basin forced with ERA5. Results in the Sahel for all model setups are acceptable (r > 0.5) but poorly correlated (r < 0.5) with both observed datasets in the Guinea region except when using parameters from Jamaare and Hadejia driven with ERA5 and when using model default parameters. For the whole Nigeria domain, simulated Aet results showed satisfactory performance ( r > 0.5) mostly in comparison with the GLEAM3.5a, both for all chirps-driven datasets and for the model default setup. This study demonstrates the potential of using the GLEAM3.5a product for water resources modeling in data-scarce locations such as Nigeria.