Determination of spatio-temporal pattern of daily precipitation concentration index over Iran

Determining the spatio-temporal variations of precipitation patterns plays a key role in water resource management, control of natural hazards, and the design of infrastructures. In this study, the spatial and temporal alterations of daily precipitation concentration index (CI) in Iran territory for the period of 1987 to 2016 was determined, considering 80 metrological stations, Which are well distributed throughout the country. In addition, the trend of annual CI variations was examined using non-parametric Mann-Kendal test. The results indicated that CI varies between 0.57 and 0.71 in Iran, considering the last three decades. The highest CI values were obtained for the Caspian Sea and Persian Gulf coastlines, indicating the concentration of rainfall in limited days in these regions. Moreover, 64 out of 80 stations have experienced an increasing trend in CI values. According to spearman tests, the significant reverse correlation was revealed between CI value and elevation from sea level, and latitude.