Variations and trends in the rain regime of Israel are analyzed for 1975–2010, when persistent global warming has been observed. Negative trend is observed over the majority of Israel, statistically significant only in the super-arid region. The decrease is significant over the majority of Israel only in the spring, reflecting a shortening of the rainy season, >3 days/decade. The dry spells are becoming longer, significantly in most of the stations. The factors affecting these variations, synoptic systems, large-scale oscillations and global temperature, were studied for extended period, 1953–2010. A simple multiple stepwise regression model applied for the inter-annual rainfall variations indicates that the occurrence of Cyprus lows is the dominant factor and the Mediterranean oscillation index, MOI2, is also a significant factor. In order to reduce the inter-annual noise and reveal inter-decadal variations, the time-series of the rainfall and its potential predictors were smoothed by 11-year window, showing an increase toward the 1990s, followed by a decrease, at a higher rate, onward. Correspondingly, the aridity lines propagated southward till the mid-1990s and then withdrew back, at a larger rate. The large-scale oscillations and the global temperature explain 83 % of the variance on the inter-decadal time-scale, half of it explained by the global temperature alone. The findings of this study support the expected poleward expansion of the Hadley cell due to global warming.
Bibliographical noteFunding Information:
Acknowledgments The authors thank the Ministry of Environmental Protection (grant number 8-810) and the Israeli Science Foundation (ISF, grant number 108/10) that funded this study. Special thanks are due to the climatology department in the Israeli Meteorology Services that cooperated in conducting this research and specifically to Dr. Noam Halfon who did the GIS maps, Mr. Avner Forshpan and Dr. Isabella Osetinski-Tzidki. We wish also to thank Mrs. Ronit Sagi for her contribution to the statistical analysis.
© 2013, Springer-Verlag Berlin Heidelberg.
- Climate change
- Climatic variations
- Cyprus low
- Large-scale oscillations
- Spatial and temporal variations