Precipitation with large temporal and spatial variations is widely used in hydrological studies. Therefore, accurate measurement of precipitation is necessary. This study aims to eva‎luate and compare three precipitation products including PERSIANN Cloud Classification System estimation (PERSIANN-CCS), Tropical Rainfall Measuring Mission (TRMM-3B42RT V7) and CPC Morphing technique (CMOROH) with ground station data in different climates and elevations across Iran on hourly, daily, monthly and annual time scales. For this purpose, 6-hour data of 52 synoptic stations with suitable distribution during of January 2003 to December 2018 were used. Precipitation data were modified by power correction method and sub-daily IDF curves (6, 12, 18 and 24 hours) of satellites and synoptic stations were extracted by both modified and unmodified methods for 5, 10, 20, 50 and 100 year return periods. The results showed that the modified method has a better performance and in addition becomes closer to the observation curve by increasing the duration of satellite curves. Also, the performance of each satellite in the development of IDF curves in different climates and elevations was eva‎luated. Three eva‎luation indices including Pearson’s correlation coefficient (Rp), relative root mean square error (RRMSE) and relative bais (RBais) and three probability indices including probability of detection (POD), false alarm ratio (FAR), and critical success index (CSI) were used to eva‎luate the accuracy of these satellite precipitation products. The results showed that TRMM satellite has more Rp and less RRMSE than other products. According to RBais, TRMM and CMORPH underestimate precipitation by 56% and 8%, respectively. But PERSIANN-CCS overestimate precipitation by 143%. In addition, this satellite detects precipitation better. The Rp of all satellites is higher in the Mediterranean climate and lower in the humid climate. PERSIANN-CCS has the best values of Rp and RMSE in the Mediterranean climate. It has the highest Rp in 1500-2100 meters and RRMSE and RBais in -24-500 meters. TRMM and CMORPH have the best Rp in Mediterranean climates and the best RMSE and RBais in arid climates. These two satellites have the best performance at 1500-2100 meters based on eva‎luation criteria. In general, most of the precipitation products of this study in the western and southwestern regions near the coast of the Persian Gulf have a good performance in estimating precipitation. The SWAT model was used to eva‎luate runoff from January 1, 2007 to December 31, 2017. In order to ensure the obtained answer, the model was calibrated and validated in SWAT-CUP software using SUFI2 algorithm. In runoff simulation based on two indices of coefficient of determination (R2) and Nash-Sutcliffe coefficient (NSE) during calibration, validation and total statistical period, respectively, equal weighting method, Bayesian weighting (BMA), CMORPH satellite, PERSIANN-CCS and TRMM-3B42RT The V7 has the best performance. Among the mentioned satellites, modeling with precipitation data of CMORPH satellite has the best output runoff for Karkheh basin. PERSIANN-CCS satellite data modeling overestimates runoff, and TRMM-3B42RT V7 satellite data modeling underestimates runoff. In addition, the equal weighting method performs better than the Bayesian weighting method (BMA). This may be due to the short statistical period used in this study or the inadequate weighting of each satellite data in order to average and achieve the best output runoff. Also, based on the non-parametric statistical test of Mann-Whitney U and the mentioned indicators, the best accepted method for outflow runoff at a significance level of 95% after modeling the runoff from synoptic stations is equal weighting method.

عليرضا گوهري

علي ترابي حقيقي، محمد جواد زارعيان

جهانگير عابدي كوپايي، شمس اله ايوبي