Investigation of Temporal Distribution of Daily Rainfall Using the Normalized Rainfall Curves (NRC) (Case Study: Tabriz Station)

In this study, by use of the daily rainfalls of Tabriz weather station the normalized rainfall curves (NRC) were investigated. For this purpose, the cumulative amount of daily rainfalls with the cumulative number of rainy days were considered and shown by and , respectively. Then, the NRCs were extracted according to the equations of  and . This approach was applied to all days and every months of the data recording time period, separately. The parameters of models were estimated using the solver option in Excel software by the optimization method. Moreover, some of the other mathematical models (including the n-th degree polynomial, power, modified power, exponential, continuous exponential, etc.) were derived for and data by the Curve Expert 1.3 software. Among the all extracted models, a model having the lowest RMSE and highest  was introduced as the most appropriate one. The results showed that, approximately, in the all cases the  model with the lowest RMSE value (0.4858 mm) and the largest amount of  (0.9996) was known as the most appropriate model to derive the NRCs of Tabriz station. Furthermore, in monthly time scale the amount of RMSE varied from 0.22 mm (in September) up to 0.67 mm (in April). The  values for these two months obtained as 0.9999 and 0.9993, respectively.