Performance Assessment of The PERSIANN and PERSIANN-CDR Satellite Precipitation Algorithms and Survey of the Irregularities Effect on It (Case Study: Helleh River Basin)

In the present study, the effect of elevation on the performance of PERSIANN and PERSIANN-CDR satellite precipitation algorithms in Helleh basin has been investigated. Satellite precipitation data with spatial resolution of 0.25⁰ in longitude and latitude, compared with 114 rain gauge stations data during a fourteen year period (2003- 2016). Also, with the use of errors zoning in the basin area, the effect of elevation on the performance of the satellite precipitation algorithms was investigated. The results showed that the PERSIANN algorithm is underestimate on different temporal and spatial scales and it had a little accuracy. In contrast, the PERSIANN-CDR algorithm was more accurate. However, the performance of the adjusted algorithm is unacceptable at daily scale. The determination coefficient of the adjusted algorithm was 0.7588 and 0.9446, monthly and annual at the cell scale respectively. Intensity-Duration-Frequency of curves The three types of data sources show that both algorithms unserestimate rainfall values at different times during different Frequency and at different times than observational values. The spatial distribution of errors of satellite precipitation algorithms relative to basin elevation showed that in both algorithms, the RMSE value increases from low to high elevation. It is recommended to be more cautious in the use of satellite precipitation algorithms for estimating precipitation in high altitudes, and in addition to applying cloud properties to satellite imagery, a correction for altitude classes should also be considered. It is recommended to be more cautious in the use of satellite precipitation algorithms for estimating precipitation in high altitudes,