Good evening. Hope this email finds you well. I would like to share something with you hope it can be interesting to those wish to compute PET in an easy way using RegCM4 output.

"Potential evaporatranspiration (PET) is an important variable for drought monitoring, hydrological and agricultural purposes. 

According to FAO, PET is calculated using Penman Monteith (PM) equation with aid of station observation, remote sensing products and machine learning (ML) techniques. However, station data only represents the site characteristics, remote sensing products are applied only where vegetated areas are available otherwise PET equals zero.

Therefore, there is an urgent need to compute PET using a simple method for the purpose of daily forecast (especially where station data is not available) or future projection under different warming scenarios. One of the promising tools is the regional climate model (e.g. RegCM4), with which PET can be calculated using the Hargreaves-Samani equation (HS); which only requires two meteorological inputs from the RegCM4: global incident solar radiation and mean air temperature.

For the HS equation to be valid over Egypt, the calculated PET needs to be calibrated using a high-resolution gridded PET dataset (hPET; Singer et al. 2021).

More details can be found in the attached poster. This topic is for discussion. Please feel free to ask any question."