Evaluation of changes in $ RDI_{st} $ index effected by different Potential Evapotranspiration calculation methods

Abstract Investigation of drought event has a great importance in the natural erctt management and water resources management planning. One of the important indexes of drought severity assessment is RDIst index, this index is B35based on ratio of precipitation (P) and potential evapotranspiration (P...
Ausführliche Beschreibung

Abstract Investigation of drought event has a great importance in the natural erctt management and water resources management planning. One of the important indexes of drought severity assessment is RDIst index, this index is B35based on ratio of precipitation (P) and potential evapotranspiration (PET) factors. Many different methods have been introduced for PET calculation. In this study results of monthly RDIst index (1 month) based on some popular PET calculation methods include: Jensen-Haise, Modified Jensen-Haise, Thornthwaite, Hargreaves-Samani, Blaney-Criddle and FAO Penman-Monteith (this method was used as reference method) with minimum data requirements were compared. In this research climatic data of 17 synoptic stations (with different climate conditions) in Iran during 1967–2014 were used to estimate PET and monthly RDIst index. Results of this paper showed that different methods of PET calculation had significant impact on RDIst index. According to results based on RMSE index Hargreaves- Samani had the most similarities with FAO Penman-Monteith method. Based on means comparison test, Blaney-Criddle and Modified Jensen-Haise methods had the most similarities with FAO Penman-Monteith (mean of RDIst index in 58.8% of stations in Thornthwaite method, 52.9% of stations in Jensen-Haise and Hargreaves-Samani methods and 71% of stations in Blaney-Criddle and Modified Jensen- Haise methods had not different by FAO Penman-Monteith). Ausführliche Beschreibung