DATE2022-05-11 17:14:39
TITLERecent Changes in the Rain Regime over the Mediterranean Climate Region of Israel and its application on coastal floods
AUTHORSHadas Saaroni (1) ,Baruch Ziv (2) ,Ron Drori (3) ,Adi Etkin (1) ,Efrat Sheffer (3)
  1. 1) Tel-aviv University, Tel-aviv (Israel) ,2) The Open University Of Israel, Ranana (Israel) ,3) The Hebrew University Of Jerusalem, Jerusalem (Israel)
ABSTRACTPrevious observational analyses have shown a declining rainfall trend over Israel, mostly statistically insignificant. Analysis of the rainfall regime combining data of river’s flow discharge from the northwestern coastal area undermines these findings, and the alarming future projections. No consistent trend is found for the annual rainfall for the period 1975-2020. This is explained by a combination of negative trend in the number of rainy days and positive trend in the daily rainfall intensity, each in the order of 2.0 %/decade. In the mid-winter, the rainfall and the daily intensity is increasing, while they both are declining in the autumn and spring, implying a contraction of the rainy season. The time span between accumulation of 10% and 90% of the annual rainfall, being 112 days on the average, has shortened by seven days during this period. This is also expressed by an increase of the Seasonality Index, indicating that the regional climate is shifting from "Markedly seasonal with a long dry season" to "Most rain in ≤ 3 months". The increase in the daily rain found significant at the northern coastal plain goes in line with an increase in flow discharge. The intra-seasonal course of the rainfall trend corresponds to that of the occurrence and intensity of the Cyprus Lows and the Mediterranean Oscillation. The sea-surface temperature was found to increase significantly, which may explain partly the increase in the daily rain intensity. The contraction of the rainy season and the increase in the daily intensity have far-reaching environmental impacts in this vulnerable region.