The study looked at different ways to measure drought severity using precipitation and evapotranspiration data. They found that the choice of evapotranspiration model can affect how severe a drought is perceived, especially for longer time periods. The Penman-Monteith model and a temperature-based model were better at estimating drought severity compared to the Thornthwaite model. This is important for areas with limited weather data, as it can impact how we understand and monitor drought conditions.