The Effect of Climate and Topographic Conditions on the Performance of PERSIANN Family Products over Iran

One of the complicated variables in hydrological and meteorological processes is precipitation. During the past decades several attempts have been carried out to developed and provide precipitation products with different spatio-temporal resolutions. The PERSIANN family products which includes PERSIANN, PERSIANN-CCs and PERSIANN-CDR is one of the most important attempts to estimate rainfall based on remote sensing techniques and cloud thickness. This research assessed the efficiency and performance of PERSIANN family products at the monthly time scale over Iran using 355 synoptic stations. In addition, evaluating the effect of climate and topographic conditions on the performance of these products is another objectives of this study. Results indicated that PERSIANN-CDR, due to using GPCP dataset for removing bias, highly correlated with observed data, while the average correlation coefficient (CC) over Iran for PERSIANN and PERSIANN-CCs is 0.49 and 0.51, respectively. Moreover, all PERSIANN products tend to underestimate rainfall in north and north-west parts of Iran, while in the south and south-east parts of the country the rate of rainfall overestimation increases significantly. Findings on the effect of topographic conditions demonstrate that in the high elevation (between 600m and 2600m) and low elevation (lower than 600m) regions the correlation between ground-gauge observations and PERSIANN family products is high and low, respectively. The performance of these datasets in the Mediterranean, semi-humid and humid climate regions is better than other climate conditions. Also, in per-humid A, per-humid B and extra arid climate regions the relative bias (RB) in rainfall estimation is very high.