Dear RegCNETs,

Good afternoon. Hope you are doing well. Based on an important question (from a collage) about difficutly of calculating the potential evapotranspiration (PET) from the RegCM5, I present an approach to overcome this problem and to calculate the PET using minimum number of variables.

I used the Hargreaves-Samani method (HS) and calibrated it with respect to the ERA5-land based product (hPET). Also, you can use the CRU as the observational dataset. Please note that there are two versions of the HS equation. Kindly check the attached papers and let me know if you have any question.

1 - https://www.researchgate.net/publication/369295676_Estimating_the_Potential_Evapotranspiration_of_Egypt_Using_a_Regional_Climate_Model_and_a_High-Resolution_Reanalysis_Dataset

2 - https://www.researchgate.net/publication/381280946_On_the_Sensitivity_of_the_Potential_Evapotranspiration_of_Egypt_to_Different_Initial_Conditions_of_the_Soil_Moisture_Using_a_High-resolution_Regional_Climate_Model

3 - https://www.researchgate.net/publication/369734593_Estimating_the_potential_evapotranspiration_of_Bulgaria_using_a_high-resolution_regional_climate_model

You can choose the HS version (includes the global incident solar radiation and daily mean air temperature; radiation-temperature version) or temperature-only version (based on daily maximum, minimum and mean air temperature) based on your area climate regime.

Hope this can help you.

Best Regards

Samy