Hadas SAARONI, Tel Aviv University, Israel
Baruch ZIV, The Open University of Israel, Israel
Ron DRORI, The Hebrew University of Jerusalem, Israel
Adi ETKIN, Tel Aviv University, Israel
Efrat SHEFFER, The Hebrew University of Jerusalem, Israel
Previous observational analyses have shown a declining rainfall trend over Israel, mostly statistically insignificant. The current study, for the period 1975-2020, undermines these findings, and the alarming future projections, and elaborates other ingredients of the rain regime. No distinct trend is found for the annual rainfall. This reflects a balance between a negative trend in the number of rainy days and a positive trend in the daily rainfall intensity, both in the order of 2.0 %/decade.
While in the mid-winter the rainfall and the daily intensity increased, they both declined in the autumn and spring, implying a contraction of the rainy season. The time span between the accumulation of 10% and 90% of the annual rainfall, being 112 days on average, was shortened by seven days during the study 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 intra-seasonal course of the rainfall trend corresponds to that of the occurrence and intensity of the Cyprus Lows and the Mediterranean Oscillation, MOI2. The sea-surface temperature was found to increase significantly, which may explain the general increase in the daily intensity. The contraction of the rainy season and the increase in the daily intensity have far-reaching environmental impacts in this vulnerable region.
Keywords: Long-term trend|Daily rainfall intensity|Drying|Seasonality Index|Effective length of the rainy season
A103806HS