Using the precipitation concentration index for characterizing the rainfall distribution in the Levant

Climate change leads to altered spatial and temporal patterns of precipitation due to activating the hydrological cycle. This study analyzes the distribution of precipitation concentration over the Levant in 1970–2018 for the first time at various time scales. The precipitation concentration index (PCI) was calculated using a quality-controlled time series from 167 meteorological stations. Trends were calculated using a Mann–Kendall nonparametric test, and a nonparametric Mann–Whitney test was used to determine the statistical significance of the differences between the mean sub-periods. The Levant can be divided into three regions, a strongly irregular concentration in south Palestine and Jordan as well as east Jordan; an irregular concentration in center/north Palestine, north Jordan, and east Syria; and a moderately irregular concentration over the Syrian coast. The annual precipitation concentration index (PCI) for the Levant, Palestine, and Syria non-significantly increased by 0.33, 0.32, and 0.22 unit/decade, respectively. Significant increasing trends occurred in the northwest of the West Bank, with averages of 0.75 unit/decade. The seasonal rainfall distribution tends to be uniform in winter and spring, mainly for south Levant, whereas the annual rainfall tends to be more concentrated. The autumn PCI significantly decreased for the Levant, Palestine, and Syria by −0.46, −0.61, and −0.54 units/decade, respectively.