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Abstracts of research articles focusing on the climate change and climate change prediction studies for the Mediterranean Region published in refereed journals during 2007 - 2015 Rubin S. Ziv B. PALDOR N. Tropical Plumes over Eastern North Africa as a Source of Rain in the Middle East MONTHLY WEATHER REVIEW 135, 4135-4148, DOI:10.1175/2007MWR1919.1, 2007 Tropical plumes (TPs) reflect tropical–extratropical interaction associated with the transport of moisture from the Tropics to extratropical latitudes. They are observed in satellite images as continuous narrow cloud bands ahead of upper-level subtropical troughs at times when the subtropical jet is highly perturbed. Rainstorms usually develop in the exit regions of TPs, so their presence over northern Africa has an impact on the precipitation regime in the southeastern Mediterranean. Based on satellite images and rainfall measurements from Israel, 10 TPs over eastern North Africa between 1988 and 2005 in which considerable rain was recorded were selected. Using the NCEP–NCAR reanalysis data, the structure and evolution of these TPs were characterized and their regional canonical features were identified. A typical TP that occurred in March 1991 is described in detail. The main canonical characteristics are as follows: the TP development is preceded by an incubation period, expressed either as a stationary upperlevel trough, persisting 2–6 days, or as two consecutive TP pulses; the preferred location for TP origin is 5°–15°N, 5°W–15°E; the TP is separated from the underlying dry Saharan PBL; the subtropical trough undergoes a phase locking with the lower tropical trough; the cloudiness in the TP-induced rainstorm is mostly stratified with continuous moderate rain, originating from midlevel moisture; and the TP tends to be followed by a midlatitude cyclogenesis over the eastern Mediterranean. This analysis proposes several explanations for the efficiency of the TPs in transporting moisture over a 2000-km distance. S. O. Krichak, P. Alpert, K. Bassat, and P. Kunin The surface climatology of the eastern Mediterranean region obtained in a three-member ensemble climate change simulation experiment Adv. Geosci., 12, 67–80, 2007 www.adv-geosci.net/12/67/2007/ Abstract. Two configurations of RegCM3 regional climatemodel (RCM) have been used to downscale results of two atmosphere-ocean global climate model (AOGCM) simulations of the current (1961–1990) and future climates (2071– 2100) over the eastern Mediterranean (EM) region. The RCM domain covering the EM region from northern Africa to central part of Asia Minor with grid spacing of 50 km was used. Three sets of RCM simulations were completed. Results of the RCM experiment support earlier projections of a temperature (annual precipitation) increase (decrease) to the end of 21st century over the EM. The roles of several major factors in controlling uncertainty of the climate change estimates are evaluated. The main uncertainty factors appear to be associated with possible inadequacies in RCM description of the EM-climate-controlling developments over remotely located areas as well as those in the simulations of the global climate and its trends by the AOGCMs. Amir Givati and Daniel Rosenfeld Possible impacts of anthropogenic aerosols on water resources of the Jordan River and the Sea of Galilee WATER RESOURCES RESEARCH, VOL. 43, W10419, doi:10.1029/2006WR005771, 2007 Abstract Insights are provided to the hitherto unexplained decreasing trends in the available water for consumption from the Sea of Galilee and in the outflow of the main springs of the Jordan River with respect to the nearby rainfall. The loss of available water of about 110 million m3 yr1 (about 6.5% of the national water consumption in Israel) is shown to be caused by a decreasing trend in the factor of precipitation enhancement by uplifting on topographic barriers. Previous studies, reviewed here, show that the most probable cause of this decreasing trend is an increasing trend in the concentrations of submicron air pollution particles during the last half century. These particles slow down the conversion of cloud drops into raindrops and snow flakes, thus decreasing precipitation from short-lived clouds such as form in moist air that crosses topographic barriers. This decreasing trend was partially mitigated by cloud seeding for rain enhancement, but apparently, the air pollution dominated and caused a net loss of orographic precipitation. A large portion of the water resources in this semiarid part of the world results from orographic precipitation. Therefore this is an issue with major economic and societal implications, not only to the study area but to many other densely populated parts of the world where the livelihood of the inhabitants depends on water resulting from orographic precipitation, which might be compromised by the air pollution produced by the very people who depend on that water. P. Alpert, N. Halfon and Z. Levin, Does air pollution really suppress precipitation in Israel?, J. Appl. Meteoro. And Climatolo., 47, 4, 933-943, 2008. Abstract Trends in the orographic rainfall ratio R0 over Israel are reevaluated. It is shown that the rainfall has not changed significantly over most of the mountainous stations, with some significant increases over the central mountains. The overall evaluation of R0 for all potential station pairs, calculating the ratio of each mountain station separately over each coastal or seashore station, indicates that about 50% of all pairs show a positive trend in R0. The high spatial variability, especially over the mountains, allows for finding orographic rainfall ratio trends that are significant in both the positive and negative directions . The correct definition of R0 in the Israeli case requires the use of a seashore cluster of stations. If some of the seashore stations are replaced by inland stations, and in particular stations that are right over the region of maximum positive rainfall urban enhancement due to the thermal heat island or other urban effects, a seemingly decreasing “orographic ratio” is unavoidable. In such a case, urban dynamical positive effects on coastal rainfall can be erroneously interpreted as pollution suppression of orographic rainfall. When seashore stations are selected as required by a proper definition of the orographic ratio, increasing R0 is obtained over central Israel and an insignificant trend over the north is found. Furthermore, evaluation of the ratio of rainfall for the upwind in comparison with the downwind side of the Galilee Mountains exhibits an increasing trend, opposite to the recent findings of Givati and Rosenfeld. The rainfall analysis shows no evidence of any suppression of rainfall over the mountains due to pollution, and at least in Israel other factors besides aerosols are predominant in defining the trends in the orographic rainfall ratio P. Alpert, S.O. Krichak, H. Shafir, D. Haim and I. Osetinsky, Climatic trends to extremes employing regional modeling and statistical interpretation over the E. Mediterranean, Global and Planetary Change, 63, 163-170, 2008. Results of regional climate modeling performed at the International Centre for Theoretical Physics, Trieste, Italy, are analyzed for the E. Mediterranean region. It is found that the average temperature over the Mediterranean area has increased by 1.5– 4 °C in the last 100 yr. The temperature in the years 2071-2100 according to the A2 and B2 scenarios are predicted to increase by about 4 °C and 6 °C respectively over Northern Israel in comparison with the control run for 1961–1990. The precipitation above most of the Mediterranean shows a dominant negative trend in the last 50 yr. A large negative trend in the A2 scenario is found over Northern Israel, while B2 scenario shows no significant trend. There is a tendency toward extreme events. It is found that the extreme precipitation over Northern Israel shows significant increasing trends for the A2 and B2 scenarios with respect to the present climate. Also, the standard deviation of the average annual precipitation is higher in the A2 and B2 scenarios showing a trend toward both drier as well as wetter years in the future A. Mariotti, N. Zeng, J. H. Yoon, V. Artale, A. Navarra, P. Alpert and Z. X. Li, Mediterranean water cycle changes: transition to drier 21st century conditions in observations and CMIP3 simulations, Environmental Research Letters, 3, 044001 (8pp) doi:10.1088/17489326/3/4/044001, 2008. Abstract We use CMIP3 multi-model simulations to show how individual hydroclimatic changes will concur to determine even greater alterations of 21st century Mediterranean water cycle characteristics, with contrasting behavior over land and sea. By 2070–2099, the average of the models predicts a 20% decrease in land surface water availability and a 24% increase in the loss of fresh water over the Mediterranean Sea due to precipitation reduction and warming-enhanced evaporation, with a remarkably high consensus among analyzed models. The projected decrease in river runoff from the surrounding land will further exacerbate the increase in Mediterranean Sea fresh water deficit. 20th century simulations indicate that the ‘transition’ toward drier conditions has already started to occur and has accelerated around the turn of the century towards the larger rates projected for the 21st century. These tendencies are supported by observational evidence of century-long negative trends in regionally averaged precipitation, PDSI and discharge from numerous rivers; and are consistent with reported increases in Mediterranean sea water salinity. Akio Kitoh, Akiyo Yatagai and Pinhas Alpert First super-high-resolution model projection that the ancient “Fertile Crescent” will disappear in this century, Hydrological Research Letters 2, 1-4 DOI: 10.3178/HRL.2.1, 2008. Abstract: The first full projections of rainfall and streamflow in the “Fertile Crescent” of Middle East are presented in this paper. Up until now, this has not been possible due to the lack of observed data and the lack of atmospheric models with sufficient resolution. An innovative super-high-resolution (20-km) global climate model is employed, which accurately reproduces the precipitation and the streamflow of the present-day Fertile Crescent. It is projected that, by the end of this century, the Fertile Crescent will lose its current shape and may disappear altogether. The annual discharge of the Euphrates River will decrease significantly (29-73%), as will the streamflow in the Jordan River. Thus countermeasures for water shortages will become much more difficult. Krichak SO, Alpert P, Kunin Projections of climate change over non-boreal east Europe during first half of twenty-first century according to results of a transient RCM experiment. In Regional aspects of climate-terrestrial-hydrologic interactions in non-boreal eastern Europe, [P.Ya. Groisman and S.V. Ivanov, eds], Springer, NATO Science for Peace and Security Series, Series C: Environmental Security, pp. 55-62. 2009 Abstract. Climate change trends over the southern east-Europe are evaluated according to results of a climate simulation experiment with the ICTP RegCM3 regional climate model driven from the lateral boundaries by results of ECHAM5/MPI-OM1 transient climate simulation from 1960 to 2060 (SRES A1B emission scenario after 2001). The trends projected include – precipitation: winter and spring – rise over the central eastEurope and drop over the eastern Mediterranean region, summer-autumn – drop over east-Europe and northern eastern-Mediterranean, rise over the Middle East (especially in autumn); 2-m air temperature: winter and spring – rise over the whole region with a maximum over its eastern and north-eastern (especially) and south-eastern parts, summer – rise with a maximum over the Middle East and minimum over north-eastern part, autumn – rise with maximum over the Caspian, Black Seas and northern areas of the European Territory of Russia. R. Samuels, A. Rimmer and P. Alpert, Effect of Extreme Rainfall Events on the Water Resources of the Jordan River, Journal of Hydrology, 375, 513-523, doi:10.1016j. hydrol.2009.07.001, 2009. As a response to climate change, shifting rainfall trends including increased multi-year droughts and an escalation in extreme rainfall events are expected in the Middle East. The purpose of this study is to evaluate the potential impact of these shifting trends on stream flow in the Jordan River and its tributaries. We use a non-homogeneous hidden Markov model to generate artificial daily rainfall simulations which capture independently shifting trends of increased droughts and escalated extreme. These simulations are then used as input into a hydrological model calibrated for the upper catchments of the Jordan River to compare the impact on stream flow and water resources between the different rainfall scenarios. We compare the predicted baseflow and surface flow components of the tested watersheds, and find that while an increase in extreme rainfall events increases the intensity and frequency of surface flow, the over all flow to the Jordan River, and the characteristics of the baseflow in the Jordan River system is not largely impacted. In addition, though it has been suggested that in the case of a multi-year drought the karstic nature of the aquifer might lead to more intense, nonlinear reductions in stream flow, here we quantify and show the conditions when annual stream flow reduce linearly with rainfall, and when these relations will become nonlinear. Simon O. Krichak Pinhas Alpert Pavel Kunin Numerical simulation of seasonal distribution of precipitation over the eastern Mediterranean with a RCM Clim Dyn DOI 10.1007/s00382-009-0649-x, 2009 Abstract Regional climate model (RCM) RegCM3 with 50 km horizontal resolution driven from the lateral boundaries by the data from NCEP/NCAR re-analysis is used in a series of ten climate downscaling experiments over the eastern Mediterranean (EM) region. Results of the experiments are characterized by seasonal precipitation patterns with notable offshore precipitation zones positioned 50 km westward of a less intense precipitation zone over the coastal area. Atmospheric processes determining the distribution of seasonal precipitation patterns in the EM are analyzed based on results of the RCM experiments performed. Level of success of the model representation of the actual precipitation over the ECM appears to be depending on that of precipitation balance over different parts of the domain. Excessive moisture convergence over a subarea usually takes place at the expense of moisture divergence from neighboring areas. Synoptic mechanism causing formation of the precipitation zone in the offshore zone appears to be associated with the role of meridionally oriented atmospheric trough systems extending from Scandinavia or Siberia to the EM during the period with rainy events. In such situations, air flows with strong northern components lead to intense transport of cold air masses to the EM. Meeting of the cold air masses the warm and humid air over the sea surface in the offshore zone causes formation of persistent squall lines and heavy rains there. Such processes may continue quite long as long as the troughs are stationary. Y. Yosef, H. Saaroni and P. Alpert, Trends in daily rainfall Intensity over Israel 1950/1-2003/4, The Open Atmospheric Science Journal, 3, 196-203, 2009 Abstract: The study focuses on long-term trends of daily rainfall in Israel as a function of their intensity in order to identify potential trends in rainfall extremity. The study period is the rainy season, October-May between 1950/1 and 2003/4. For the total rainfall, an increased trend is shown across Israel, especially for the central and southern regions, though non-significant. Daily rainfall intensity showed non-significant trends of increase in the heavy rainfall at the center and south and decrease at the north. The light to moderate rainfall trends increased in the north while they decreased at the center and south. Trends are significantly correlated with known teleconnection patterns, especially the East Atlantic- Western Russia and the North Sea-Caspian Sea patterns. Positive trends toward heavier rainfall are noted in Israel, which are significant in several specific locations. This finding has to be carefully followed since the region is a climatic border subjected to severe water shortage and is predicted to dry-up in most global warming scenarios. N. Halfon, Z. Levin and P. Alpert, Temporal rainfall fluctuations in Israel and their possible link to urban and air pollution effects, Environ. Res. Lett. 4, (12pp), doi:10.1088/1748-9326/4/2/025001, 2009. Abstract In this paper we analyze spatial variations of the annual rainfall that have taken place in the non-arid regions of Israel (annual rainfall >200 mm) during the years 1952– 2006, incorporating all available data. The results of the present study over the research area as a whole indicate that no significant temporal change of the annual rainfall occurred in any region of the study area. However, focusing on spatial rainfall fluctuations between sub-regions in the study area, a significant increase was observed between the stations located downwind and those upwind of the Greater Tel Aviv region. This increase supports previous reports showing that rainfall enhancement is observed downwind (and close) to urban centers. In contrast to a few previous reports, no decrease in the ratio between the mountain precipitation to that over the coastal region was found. Over the period of the present study, the rainfall ratio between the upwind slopes and the seashore remained unchanged, with a slight increase in the central part of the country. The only hilly place where a slight decrease in annual rainfall was observed is the lee side (eastern slopes) of the Galilee Mountains. This result is important because the eastern slopes of the Galilee Mountains have for years been part of the target area for Israeli artificial cloud seeding for rain enhancement. The results therefore suggest that unless there was a pronounced change in the synoptic conditions during rain spells, seeding in Israel had no positive effect on rainfall amounts Samuels R, Rimmer A, Hartman, A., Krichak SO, Alpert P Climate Change impacts on the Jordan River, Israel: Downscaling application from a Regional Climate Model, J. Hydrometeorology, 11, 860-879, 2010, Abstract. The integration of climate change projections into hydrological and other response models used for water resource planning and management is challenging given the varying spatial resolutions of the different models. In general, climate models are generated at spatial ranges of hundreds of kilometers, while hydrological models are generally watershed specific and based on input at the station or local level. This paper focuses on techniques applied to downscale large-scale climate model simulations to the spatial scale required by local response models (hydrological, agricultural, soil). Specifically, results were extracted from a regional climate model (RegCM) simulation focused on the Middle East, which was downscaled to a scale appropriate for input into a local watershed model [the Hydrological Model for Karst Environment (HYMKE)] calibrated for the upper Jordan River catchment. With this application, the authors evaluated the effect of future climate change on the amount and form of precipitation (rain or snow) and its effect on streamflow in the Jordan River and its tributaries—the major water resources in the region. They found that the expected changes in the form of precipitation are nearly insignificant in terms of changing the timing of streamflow. Additionally, the results suggest a future increase in evaporation and decrease in average annual rainfall, supporting expected changes based on global models in this region. Debbie Hemming, Carlo Buontempo, Eleanor Burke, Mat Collins and Neil Kaye How uncertain are climate model projections ofwater availability indicators across the Middle East? Phil. Trans. R. Soc. A 2010 368, doi: 10.1098/rsta.2010.0174,2010. The projection of robust regional climate changes over the next 50 years presents a considerable challenge for the current generation of climate models. Water cycle changes are particularly difficult to model in this area because major uncertainties exist in the representation of processes such as large-scale and convective rainfall and their feedback with surface conditions. We present climate model projections and uncertainties in water availability indicators (precipitation, run-off and drought index) for the 1961–1990 and 2021–2050 periods. Ensembles from two global climate models (GCMs) and one regional climate model (RCM) are used to examine different elements of uncertainty. Although all three ensembles capture the general distribution of observed annual precipitation across the Middle East, the RCM is consistently wetter than observations, especially over the mountainous areas. All future projections show decreasing precipitation (ensemble median between −5 and −25%) in coastal Turkey and parts of Lebanon, Syria and Israel and consistent run-off and drought index changes. The Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) GCM ensemble exhibits drying across the north of the region, whereas the Met Office Hadley Centre work Quantifying Uncertainties in Model Projections—Atmospheric (QUMP-A) GCM and RCM ensembles show slight drying in the north and significant wetting in the south. RCM projections also show greater sensitivity (both wetter and drier) and a wider uncertainty range than QUMP-A. The nature of these uncertainties suggests that both large-scale circulation patterns, which influence region-wide drying/wetting patterns, and regional-scale processes, which affect localized water availability, are important sources of uncertainty in these projections. To reduce large uncertainties in water availability projections, it is suggested that efforts would be well placed to focus on the understanding and modelling of both large-scale processes and their teleconnections with Middle East climate and localized processes involved in orographic precipitation. F. Jin, J., A. Kitoh and P. Alpert, Water cycle changes over the Mediterranean: a comparison study of a super-high-resolution global model with CMIP3. Phil. Trans. Roy. Soc. A., 368, 1-13, 2010. Water cycle components over the Mediterranean for both a current run (1979–2007) and a future run (2075–2099) are studied with the Japan Meteorological Agency’s 20 km grid global climate model. Results are compared with another study using the Coupled Model Intercomparison Project Phase 3 ensemble model (hereafter, the Mariotti model). Our results are surprisingly close to Mariotti’s. The projected mean annual change rates of precipitation (P) between the future and the current run for sea and land are − 11 per cent and −10 per cent, respectively, which are not as high as Mariotti’s. Projected changes for evaporation (E) are+9.3 per cent and−3.6 per cent, compared with +7.2 per cent and −8.1 per cent in Mariotti’s study, respectively. However, no significant difference in the change in P–E over the sea body was found between these two studies. The increased E over the eastern Mediterranean was found to be higher than that in the western Mediterranean, but the P decrease was lower. The net moisture budget, P-E , shows that the eastern Mediterranean will become even drier than the western Mediterranean. The river model suggests decreasing water inflow to the Mediterranean of approximately 36 per cent (excluding the Nile) H. Saaroni, N. Halfon, B. Ziv, P. Alpert and H. Kutiel, Links between the rainfall regime in Israel and location and intensity of Cyprus Lows, Int. J. Climatol., 30, 1014-1025, DOI: 10.1002/joc.1912, 2010. ABSTRACT: The interannual variations and the spatial distribution of rainfall in the Mediterranean and semi-arid regions of Israel are analysed with respect to variations in the occurrence e of the typical synoptic systems of the Eastern Mediterranean. The synoptic analysis is based on a daily, semi-objective synoptic classification. The study covers the months November – March, in which 90% of the annual rainfall is obtained, mostly resulting from Cyprus lows. The interannual variations of the rainfall are well explained by the synoptic types, and the occurrences of Cyprus lows are highly correlated with the rainfall. It was found that the daily and seasonal rainfall are highly dependent on the depth of the cyclone. Moreover, deep lows are more effective for the mountainous regions, due both to the enhanced orographic effect and to the fact that stronger winds, associated with deep lows, are more efficient in transporting rain-producing clouds from the Mediterranean Sea inland. The location of the cyclone determines the spatial distribution of the rain it produces over Israel. The cyclones located east of Cyprus were found productive mainly for the southern parts of the study region, while those located to the west and north of Israel were found productive for the north of the country. The high sensitivity of the rainfall to the location of the surface cyclones emphasizes the major role that lower level moisture transport plays in rain formation. S. O. Krichak & J. S. Breitgand & R. Samuels & P. AlpertA double-resolution transient RCM climate change simulation experiment for near-coastal eastern zone of the Eastern Mediterranean region, Theor Appl Climatol 10.1007/s00704-010-0279-6, 2011 103:167–195, DOI Abstract A double-resolution regional experiment on hydrodynamic simulation of climate over the eastern Mediterranean (EM) region was performed using an International Center for Theoretical Physics, Trieste RegCM3 model. The RegCM3 was driven from the lateral boundaries by the data from the ECHAM5/MPI-OM global climate simulation performed at the MPI-M, Hamburg and based on the A1B IPCC scenario of greenhouse gases emission. Two simulation runs for the time period 1960-2060, employing spatial resolutions of 50 km/ 14 L and 25 km/18 L, are realized. Time variations of the differences in the space distributions of simulated climate parameters are analyzed to evaluate the role of smaller scale effects. Both least-square linear and non-linear trends of several characteristics of the EM climate are evaluated in the study. One of the key findings with regard to linear trends is a notable and statistically significant precipitation drop over the near coastal EM zone during December-February and SeptemberNovember. Statistically significant positive air temperature trends are projected over the entire EM region during the four seasons. Also projected are increases in air temperature extremes and the relative contribution of convective processes in the Southern Mediterranean coastal zone (ECM) region. A notable sensitivity of projected larger-scale climate change signals to smaller-scale effects is also demonstrated. Smiatek, G. ; Kunstmann, H. ; Heckl, A. High‐resolution climate change simulations for the Jordan River area, Journal of Geophysical Research: Atmospheres, Vol.116(D16), 2156-2202 ; DOI: 10.1029/2010JD015313 , 2011 Abstract: For the estimation of future climate conditions in the Jordan River region, the National Center for Atmospheric Research–Penn State University meteorology model in the versions 3.5 and 3.7 driven with boundary data from the Max‐Planck‐Institute for Meteorology and Hadley Centre global circulation models and the Special Report on Emission Scenarios A1B emission scenario has been used. The spatial resolution of the nested dynamic downscaling approach was 18.6 km, and the transient runs were performed for the period 1960–2099. The investigated statistics include mean precipitation, frequency and intensity of wet days and strong precipitation events, as well as mean temperature and heat wave duration index. The results show that the models satisfactorily reproduce the mean temperature and precipitation patterns. The comparison with the observational reference for the period 1961–1990 reveals a bias in the annual mean precipitation ranging from −20% to +17%, with an ensemble mean of −3%. The models show limitations in reproducing the precipitation seasonality. All models underestimate the wet day frequency and show differences in the strong precipitation events. The simulations of the future climate signal indicate an ensemble mean increase of the annual mean temperature of approximately 2.1 K in the period 2031–2060 and 3.7 K for the period 2070–2099 related to the 1961–1991 mean. In the same periods, the annual mean precipitation is simulated to decrease by approximately −11.5% and −20%, respectively, which means a reduction of expected water availability in the Jordan River region. All models show an increase of the heat wave duration index. A significant elevation dependence is present in the simulated future climate signal on both temperature and precipitation. The simulations show an increased coefficient of variation in annual precipitation, indicating that larger interannual precipitation variability can be expected in the future. Significant reduction of expected water availability in the Jordan River region Significant elevation signal present in the simulated future climate Increased coefficient of variation in simulated future annual precipitation Shohami, David ; Dayan, Uri ; Morin, Efrat Warming and drying of the eastern Mediterranean: Additional evidence from trend analysis Journal of Geophysical Research. Atmospheres, 116(22) DOI: 10.1029/2011JD016004, 2011 Abstract: Trends in atmospheric variables over EM indicate warmer and drier conditions Significant warming was found in surface station summer temperature data Precipitation trends are negative but insignificant due to high natural variance The climate of the eastern Mediterranean (EM), at the transition zone between the Mediterranean climate and the semi-arid/arid climate, has been studied for a 39-year period to determine whether climate changes have taken place. A thorough trend analysis using the nonparametric Mann-Kendall test with Sen's slope estimator has been applied to ground station measurements, atmospheric reanalysis data, synoptic classification data and global data sets for the years 1964-2003. In addition, changes in atmospheric regional patterns between the first and last twenty years were determined by visual comparisons of their composite mean. The main findings of the analysis are: 1) changes of atmospheric conditions during summer and the transitional seasons (mainly autumn) support a warmer climate over the EM and this change is already statistically evident in surface temperatures having exhibited positive trends of 0.21°C/decade; 2) changes of atmospheric conditions during winter and the transitional seasons support drier conditions due to reduction in cyclogenesis and specific humidity over the EM, but this change is not yet statistically evident in surface station rain data, presumably because of the high natural precipitation variance masking such a change. The overall conclusion of this study is that the EM region is under climate change leading to warmer and drier conditions. Rimmer, A; Givati, A; Samuels, R; Alpert, P Using ensemble of climate models to evaluate future water and solutes budgets in Lake Kinneret, Israel Journal of Hydrology, Vol.410(3-4), pp.248-259, DOI: 10.1016/j.jhydrol.2011.09.025, 2011 Abstract: Identifying and quantifying future climate effects on water resources has major economic and societal implications, rendering such studies extremely important for water planners. Here we integrate output from one high resolution global (Japan Meteorological Agency) and three regional (ECHAM-RegCM, Hadley-MM5, ECHAM-MM5) climate models into three hydrological tools (1. annual incoming water volumes; 2. evaporation from the lake; and 3. lake salinity) to provide first approximations of climate change impacts on water quantity and quality in Lake Kinneret (also known as Sea of Galilee), the major freshwater resource in Israel. Meteorological data extracted from the climate models were used as input data into the models. Results were calculated for the historical 1979–2009 and the future 2015–2060 periods. The modeled historical period was verified against observed data, first by each model alone, and then by the combined model structure. Predicted results varied between the climate models. The ECHAM-RegCM predicted decreased precipitation in an average rate of 7 mm year1 (0.8% annually) while the trends of precipitation predicted by the other models were less obvious. According to the combination of ECHAM-RegCM, ECHAM-MM5 and Hadley-MM5 with the lake evaporation model, the evaporation will increase by 0.2–0.6 Mm3 (0.10–0.25%) annually while according to the JMA no trend was found. The lake salinity is mostly impacted by changes in inflows and therefore only the ECHAM-RegCM predicted significant increase of salinity (from 280 ppm Cl today to 450 ppm Cl in 2060), while the trends of salinity according to other models were mild. R. Samuels, G. Smiatek, S. Krichak, H. Kunstmann, P. Alpert, Extreme Value Indicators in highly resolved Climate Change Simulations for the Jordan River Area. J. Geoph. Res., 116, D24123, 9 pp., doi:10.1029/2011JD016322, 2011 Abstract. Understanding and predicting changing trends and frequency of extreme rainfall and temperature events are extremely important for optimal planning in many sectors including agriculture, water resource management, health and even economics. For people living in the Jordan River region of the Middle East such changes can have immediate devastating impacts as water resources are already scarce and over-exploited and summer temperatures in the desert regions can reach 45 degrees or higher. Understanding and forecasting shifts in frequency and intensity of extreme events can provide crucial information for planning and adaptation. In this paper we present results from regional climate model simulations with RegCM3 and MM5 centered on the Eastern Mediterranean region. Our analysis focusses on changes in extreme temperature and rainfall events. We show that maximum daily summer temperature is expected to increase by between 2.5-3◦16 C with an increase in warm spell length. Precipitation extremes are expected to increase with longer dry spells, shorter wet spells and increases in heavy rainfall. Model agreement for the control period 1961-1990 is higher in the southern region than in the north, perhaps due to the complex topography suggesting that even small differences in spatial scale play an important role. In addition, we notice that the chosen global model plays an important role in determining future temperature trends while the choice of regional climate model is critical for understanding how precipitation is expected to evolve. Z. Levin, N. Halfon and P. Alpert, Reply to comment by Ben-Zvi, A., D. Rosenfeld and A. Givati on the paper-Levin, Z., N. Halfon and P. Alpert, Reassessment of rain experiments and operations in Israel including synoptic considerations, Atmos. Res. 97, 513-525. DOI 10.1016 J. Atmosres.2010.06.011, Atm. Res., 99, 593-596, 2011. Abstract: Levin et al. (2010 ; hereafter LHA) (Levin, Z., Halfon, N., Alpert, P., 2010. Reassessment of rain experiments and operations in Israel including synoptic considerations. Atmos. Res. 97, 513–525. DOI:10.1016/j.atmosres.2010.06.011.), reanalyzed the results of the operational seeding in northern Israel between 1975 and 2007 and the preceding Israel 2 cloud seeding experiment (1969–1975) and concluded that there is no net increase in precipitation over the target areas. Our analysis revealed that a synoptic bias during Israel 2 is one of the reasons for the apparent positive effect of seeding in the northern target area and the negative effect in the southern area both of which disappeared in the following experiment in the south (Israel 3; 1975–1995) and the operational seeding in the north. Ben-Zvi et al. (2010 ;hereafter BRG) criticized our paper primarily on the ground that we did not consider the positive results of Israel 1 experiment (1960–1967). It should be noted that in Israel 1 different seeding lines were used from those in both Israel 2 and the operational period. In addition, its raw data is not accessible anymore for reanalysis. Furthermore, Israel 2 had been designed as a confirmatory cross-over experiment to Israel 1 and failed to reproduce its promising results with double ratio (DR) of ~1.00, namely, zero rainfall enhancements. The same DR values were also found in Israel 3 and in the operational seeding. Therefore, because of the differences in the two experiments, the lack of access to the raw data and the disappointing results of the confirmatory experiment, we decided to concentrate our analysis on the more recent seeding activities. The attempt by BRG to explain the reduction of the DR to ~1.00 in the operational seeding period by the suppression due to pollution have been disproved by Alpert et al. (2008, 2009) and also fail to explain the sharp decline of the target/control ratio right at the beginning of the operational seeding period when the lucky draw in this area came to its end (see LHA). F. Jin,, A. Kitoh, and P. Alpert, Climatological relationships among the moisture budget components and rainfall amounts over the Mediterranean based on a superhigh-resolution climate model, J. Geophys. Res., 116, D09102, doi:10.1029/2010JD014021, 2011. Moisture budget components over a rectangular region defined by the longitudes 6.0°W–36.0°E and latitudes 30.0°N to 45.0°N, with an area of about 6.08 × 106 km2 over the Mediterranean (Med) Basin, are studied by the use of the Japan Meteorological Agency super ‐ high‐ resolution (20 km) GCM monthly mean data. The research time periods are 1979–2007 for current run and 2075– 2099 for future run. Six rainy months of October to March with a total of 168 months for the current run and 144 months for the future run were selected. The rain months have been categorized into five groups of months based on the mean monthly rainfall amounts where the five groups are P < 1.0, 1.0≤P < 1.5, 1.5≤P < 2.0, 2.0≤P < 2.5, and 2.5 mm/d ≤ P. We found that generally, over the Mediterranean, the outflow‐ inflow is balancing the independently calculated evaporation ‐ precipitation quite well with a correlation coefficient of about 0.89. The present seasonal (October‐March) precipitation simulated from the 20 km GCM showed a quite reasonable agreement with the CRU. The seasonal area mean precipitation and evaporation are 1.85 mm/d and 2.44 mm/d, respectively. The largest two precipitation categories contribute over 50% of the total seasonal rainfall. The evaporation varies positively with the precipitation for all precipitation categories. Also, the relatively high mean recycling ratio (55%) indicates that the local Med evaporation has a central role in the local precipitation. Another important finding is that the decreasing trend of recycling ratio with the rising of the precipitation category implies that the outside moisture inflow role increases with the increase of the precipitation category. For all the precipitation categories, the total outflow is larger than the total inflow, indicating that the Med area is an important source of moisture. Individual boundary moisture flux shows that the main moisture comes from the west boundary and contributes 59% of the total inflow, while the main outflow is through east boundary and is responsible for 46% of total outflow. Analysis of monthly precipitation indicates that the October and November have the two largest amount of precipitation over the research region. The moisture budget study separated for the east and the west Med shows that the area mean precipitation for the east and the west Med are 2.14 and 2.29 mm/d, while the evaporation are 4.48 and 3.59 mm/d. The plausible reason for the differences between these two basins has been discussed. The moisture supplies to the east Med is mainly from the west boundary, while for the west Mediterranean, the north boundary inflow also plays an important role along with the west boundary. The future moisture budget components over Med suggest that the precipitation is decreasing from 1.85 to 1.62 mm/d and the evaporation is increasing from 2.44 to 2.56 mm/d between current and future. Another finding is that the largest precipitation number of months decreases from 12% to only 6% of the total number of months, while the intensity of the precipitation in this category enhances in the future Wanli Wu, Yubao Liu, Ming Ge, Dorita Rostkier-Edelstein, Gael Descombes, Pavel Kunin, Thomas Warner, Scott Swerdlin, Amir Givati, Thomas Hopson, David Yates Statistical downscaling of climate forecast system seasonal predictions for the Southeastern Mediterranean, Atmospheric Research 118, 346–356, 2012 Abstract Most of the annual rainfall in the Southeastern Mediterranean falls in the wet season from November to March. It is associated with Mediterranean cyclones, and is sensitive to climate variability. Predicting the wet season precipitation with a few months advance is highly valuable for water resource planning and climate-associated risk management in this semi-arid region. The regional water resource managements and climate-sensitive economic activities have relied on seasonal forecasts from global climate prediction centers. However due to their coarse resolutions, global seasonal forecasts lack regional and local scale information required by regional and local water resource managements. In this study, an analog statistical-downscaling algorithm, knearest neighbors (KNN), was introduced to bridge the gap between the coarse forecasts from global models and the needed fine-scale information for the Southeastern Mediterranean. The algorithm, driven by the NCEP Climate Forecast System (CFS) operational forecast and the NCEP/DOE reanalysis, provides monthly precipitations at 2– 4 months of lead-time at 18 stations within the major regional hydrological basins. Largescale predictors for KNN were objectively determined by the correlations between the station historic daily precipitation and variables in reanalysis and CFS reforecast. Besides a single deterministic forecast, this study constructed sixty ensemble members for probabilistic estimates. The KNN algorithm demonstrated its robustness when validated with NCEP/DOE reanalysis from 1981 to 2009 as hindcasts before applied to downscale CFS forecasts. The downscaled predictions show fine-scale information, such as stationto-station variability. The verification against observations shows improved skills of this downscaling utility relative to the CFS model. The KNN-based downscaling system has been in operation for the Israel Water Authority predicting precipitation and driving hydrologic models estimating river flow and aquifer charge for water supply. Kelley, C., M. Ting, R. Seager, and Y. Kushnir, Mediterranean precipitation climatology, seasonal cycle, and trend as simulated by CMIP5, Geophys. Res. Lett., 39, L21703, doi:10.1029/2012GL053416, 2012 Winter and summer Mediterranean precipitation climatology and trends since 1950 as simulated by the newest generation of global climate models, the Coupled Model Intercomparison Project phase 5 (CMIP5), are evaluated with respect to observations and the previous generation of models (CMIP3) used in the Intergovernmental Panel on Climate Change Fourth Assessment Report. Observed precipitation in the Mediterranean region is defined by wet winters and drier summers, and is characterized by substantial spatial and temporal variability. The observed drying trend since 1950 was predominantly due to winter drying, with very little contribution from the summer. However, in the CMIP5 multimodel mean, the precipitation trend since 1950 is evenly divided throughout the seasonal cycle. This may indicate that in observation, multidecadal internal variability, particularly that associated with the North Atlantic Oscillation (NAO), dominates the wintertime trend. An estimate of the observed externally forced trend shows that winter drying dominates in observations but the spatial patterns are grossly similar to the multimodel mean trend. The similarity is particularly robust in the eastern Mediterranean region, indicating a radiatively forced component being stronger there. Results of this study also reveal modest improvement for the CMIP5 multi-model ensemble in representation of the observed six month winter and summer climatology. The results of this study are important for assessment of model predictions of hydroclimate change in the Mediterranean region, often referred to as a “hotspot” of future subtropical drying. Rana Samuels, Maayan Harel, Pinhas Alpert , A new methodology for weighting high-resolution model simulations to project future rainfall in the Middle EastClim Res. Vol. 57: 51–60, doi: 10.3354/cr01147, 2013 ABSTRACT: A divergence metric was used to combine 4 high-resolution climate models to generate more reliable simulations of future rainfall. The approach is based on the assumption that the use of multiple models (an ensemble) is superior to the use of a single model, even if one of the models is shown to better capture past trends. Such an approach is especially useful in areas with steep climatic gradients, where large-scale climate models are not effective in capturing orographic and local effects. We applied the methodology to the Middle East, and specifically to Israel, where climate shifts from arid to humid temperate occur over a distance of around 400 km. Model weights were determined by calculating the similarity between the probability distributions of the models and those of the historical data using the Jenson-Shannon divergence metric. These weights were then applied to future model projections. Annual amounts of rainfall, numbers of wet days and numbers of 3 d wet spells were analyzed. Compared with observed data, the weighted ensemble outperformed the equal weights ensemble, which outperformed the best model. For the northern and central stations, average annual amounts of rainfall decreased in both near- and far-future periods, with most of the change occurring at the peak and in the left-hand tail and less change in the right-hand tail of the probability distribution. This, combined with the change in the right-hand tail of the distribution in numbers of wet spells in the near future, suggests that the decline in overall rainfall will be higher than the corresponding decline in extreme events; or in other words even though there will be less rainfall, the extreme events will remain, and even possibly increase. In the south, a mixed trend of slightly increasing median amounts of rainfall and slightly decreasing extreme events is projected. Amir Givati, Daniel Rosenfeld The Arctic Oscillation, climate change and the effects on precipitation in Israel Atmospheric Research 132–133 114–124, http://dx.doi.org/10.1016/j.atmosres.2013.05.001, 2013 The Arctic Oscillation (AO) has been found in previous studies to be a major synoptic factor affecting the climate of many regions in the high and mid-latitudes. This paper demonstrates the physical process by which the AO affects the climate of the Eastern Mediterranean basin, with a focus on precipitation in Israel as a case study. It is shown that a trend of increasing AO is associated with a substantial decrease of winter precipitation from the Iberian Peninsula, though Italy, Greece, Turkey and Cyprus, as well as Lebanon, Syria and also the northern parts of Israel. Winter rain is slightly increased in the southern coast of the eastern half of the Mediterranean Sea. The immediate meteorological causes are shown to be a larger northerly component of the flow over the Mediterranean Sea, associated with a decreasing relative humidity and stability, except over the southern coast, where the air mass has the longest track over the relatively warm water. We suggest here that the observed changes in air flow that drives the precipitation trends can be explained by shifts in the AO that can be partially explained by increasing greenhouses gases. Results from the IPCC multi climate models show that the AO will continue to increase during the 21st century. This increase may lead to a continuation of the trends discussed here. The importance of the analysis provided here is in pointing out the possibility that processes that have been predicted by global warming and changes in global circulation have already started to affect precipitation and major water resources in the Mediterranean basin. D. Rostkier-Edelstein, Y. Liu, W. Wu, P. Kunin, A. Givati and M. Ge Towards a high-resolution climatography of seasonal precipitation over Israel Int. J. Climatol. DOI: 10.1002/joc.3814, 2013 ABSTRACT: This study demonstrates the capability of the Weather Research and Forecasting (WRF) model with four dimensional data assimilation (WRF-FDDA) to produce a high-resolution climatography of seasonal precipitation over Israel and the surrounding areas. The system was used to dynamically downscale global Climate Forecast System (CFS) reanalysis with continuous assimilation of conventional and unconventional observations. Precipitation seasons (December- January-February) in 7 years, including two extreme dry and wet seasons observed in the past decades, were generated at 2-km spatial resolution. Verification against rain-gauge observations shows that the WRF-FDDA system effectively reproduces the spatial and inter-annual variability, as well as the timing, intensity, and length of wet and dry spells. The best agreement between model and observations was obtained at areas dominated by complex terrain, illustrating the benefit of the high-resolution lower boundary forcing in the dynamical downscaling process. In contrast, some biases were observed over coastal-flat terrain. The model was able to reproduce some of the extreme events, but exhibited limitations in the case of rare events. This specific discrepancy between the model and observations suggests that further fine tuning and different model configurations may be needed to correctly simulate extreme events. The use of an objective weather regimes verification procedure reveals the skill of the climatography for different types of extratropical cyclones: while biases are larger at coastal-flat areas under shallow-cyclonic conditions, deep-cyclonic conditions lead to more significant biases in complex terrain regions. The weather-regimes dependent information may be used for further calibration of the downscaled precipitation. Baruch Ziv • Hadas Saaroni • Roee Pargament • Tzvi Harpaz • Pinhas Alpert Trends in rainfall regime over Israel, 1975–2010, and their relationship to largescale variability Reg Environ Change DOI 10.1007/s10113-013-0414-x, 2013. Abstract 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, largescale 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 interdecadal 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. T. Tornros and L. Menzel, Addressing drought conditions under current and future climates in the Jordan River region Hydrol. Earth Syst. Sci., 18, 305–318, www.hydrol-earth-syst-sci.net/18/305/2014/ doi:10.5194/hess-18-305-2014, 2014 Abstract. The Standardized Precipitation–Evaporation Index (SPEI) was applied in order to address the drought conditions under current and future climates in the Jordan River region located in the southeastern Mediterranean area. In the first step, the SPEI was derived from spatially interpolated monthly precipitation and temperature data at multiple timescales: accumulated precipitation and monthly mean temperature were considered over a number of timescales – for example 1, 3, and 6 months. To investigate the performance of the drought index, correlation analyses were conducted with simulated soil moisture and the Normalized Difference Vegetation Index (NDVI) obtained from remote sensing. A comparison with the Standardized Precipitation Index (SPI), i.e., a drought index that does not incorporate temperature, was also conducted. The results show that the 6- month SPEI has the highest correlation with simulated soil moisture and best explains the interannual variation of the monthly NDVI. Hence, a timescale of 6 months is the most appropriate when addressing vegetation growth in the semiarid region. In the second step, the 6-month SPEI was derived from three climate projections based on the Intergovernmental Panel on Climate Change emission scenario A1B. When comparing the period 2031–2060 with 1961–1990, it is shown that the percentage of time with moderate, severe and extreme drought conditions is projected to increase strongly. To address the impact of drought on the agricultural sector, the irrigation water demand during certain drought years was thereafter simulated with a hydrological model on a spatial resolution of 1 km. A large increase in the demand for irrigation water was simulated, showing that the agricultural sector is expected to become even more vulnerable to drought in the future. Barıs¸ Onol, Deniz Bozkurt , Ufuk Utku Turuncoglu, Omer Lutfi Sen, H. Nuzhet Dalfes. Evaluation of the twenty-first century RCM simulations driven by multiple GCMs over the Eastern Mediterranean–Black Sea region Clim Dyn 42:1949–1965 DOI 10.1007/s00382-013-1966-7, 2014 Abstract In this study, human-induced climate change over the Eastern Mediterranean– Black Sea region has been analyzed for the twenty-first century by performing regional climate model simulations forced with large-scale fields from three different global circulation models (GCMs). Climate projections have been produced with Special Report on Emissions Scenarios A2, A1FI and B1 scenarios, which provide greater diversity in climate information for future period. The gradual increases for temperature are widely apparent during the twenty-first century for each scenario simulation, but ECHAM5driven simulation generally has a weaker signal for all seasons compared to CCSM3 simulations except for the Fertile Crescent. The contrast in future temperature change between the winter and summer seasons is very strong for CCSM3-A2-driven and HadCM3-A2-driven simulations over Carpathians and Balkans, 4–5 _C. In addition, winter runoff over mountainous region of Turkey, which feeds many river systems including the Euphrates and Tigris, increases in second half of the century since the snowmelt process accelerates where the elevation is higher than 1,500 m. Moreover, analysis of daily temperature outputs reveals that the gradual decrease in daily minimum temperature variability for January during the twenty-first century is apparent over Carpathians and Balkans. Analysis of daily precipitation extremes shows that positive trend is clear during the last two decades of the twenty-first century over Carpathians for both CCSM3-driven and ECHAM5-driven simulations. Multiple-GCM driven regional climate simulations contribute to the quantification of the range of climate change over a region by performing detailed comparisons between the simulations. GERHARD SMIATEK HARALD KUNSTMANN ANDREAS HECKL HighResolution Climate Change Impact Analysis on Expected Future Water Availability in the Upper Jordan Catchment and the Middle East, JOURNAL OF HYDROMETEOROLOGY, 15, 1517-1531, DOI: 10.1175/JHM-D-13-0153.1, 2014. ABSTRACT The impact of climate change on the future water availability of the upper Jordan River (UJR) and its tributaries Dan, Snir, and Hermon located in the eastern Mediterranean is evaluated by a highly resolved distributed approach with the fifthgeneration Pennsylvania State University–NCAR Mesoscale Model (MM5) run at 18.6and 6.2-kmresolution offline coupled with theWater Flow and Balance SimulationModel (WaSiM). The MM5 was driven with NCEP reanalysis for 1971–2000 and with Hadley Centre Coupled Model, version 3 (HadCM3), GCM forcings for 1971–2099. Because only one regional–global climate model combination was applied, the results may not give the full range of possible future projections. To describe the Dan spring behavior, the hydrological model was extended by a bypass approach to allow the fast discharge components of the Snir to enter the Dan catchment. Simulation results for the period 1976–2000 reveal that the coupled system was able to reproduce the observed discharge rates in the partially karstic complex terrain to a reasonable extent with the highresolution 6.2-km meteorological input only. The performed future climate simulations show steadily rising temperatures with 2.2K above the 1976–2000 mean for the period 2031–60 and 3.5K for the period 2070–99. Precipitation trends are insignificant until the middle of the century, although a decrease of approximately 12% is simulated. For the end of the century, a reduction in rainfall ranging between 10% and 35%can be expected. Discharge in the UJR is simulated to decrease by 12%until 2060 and by 26%until 2099, both related to the 1976–2000mean. The discharge decrease is associated with a lower number of high river flow years. Giuseppe Zappa Matthew K. Hawcroft Len Shaffrey Emily Black · David J. Brayshaw Extratropical cyclones and the projected decline of winter Mediterranean precipitation in the CMIP5 models, Clim Dyn DOI 10.1007/s00382014-2426-8, 2014 Abstract The Mediterranean region has been identified as a climate change “hot-spot” due to a projected reduction in precipitation and fresh water availability which has potentially large socio-economic impacts. To increase confidence in these projections, it is important to physically understand how this precipitation reduction occurs. This study quantifies the impact on winter Mediterranean precipitation due to changes in extratropical cyclones in 17 CMIP5 climate models. In each model, the extratropical cyclones are objectively tracked and a simple approach is applied to identify the precipitation associated to each cyclone. This allows us to decompose the Mediterranean precipitation reduction into a contribution due to changes in the number of cyclones and a contribution due to changes in the amount of precipitation generated by each cyclone. The results show that the projected Mediterranean precipitation reduction in winter is strongly related to a decrease in the number of Mediterranean cyclones. However, the contribution from changes in the amount of precipitation generated by each cyclone are also locally important: in the East Mediterranean they amplify the precipitation trend due to the reduction in the number of cyclones, while in the North Mediterranean they compensate for it. Some of the processes that determine the opposing cyclone precipitation intensity responses in the North and East Mediterranean regions are investigated by exploring the CMIP5 intermodel spread. Simon O. Krichak & Joseph S. Breitgand & Silvio Gualdi & Steven B. Feldstein Teleconnection–extreme precipitation relationships over the Mediterranean region Theor Appl Climatol 117:679–692 DOI 10.1007/s00704-013-1036-4, 2014 Abstract The relationship between five teleconnection patterns (North Atlantic Oscillation (NAO), Arctic Oscillation (AO), East Atlantic/Western Russian (EAWR) pattern, Scandinavian (SCAND) pattern, and El Niño Southern Oscillation (ENSO)) and the frequency of occurrence of days (per month) with extreme precipitation in the EuroMediterranean region is investigated with National Centers for Environmental Prediction–National Center for Atmospheric Research reanalysis data. To quantify the teleconnection–precipitation relationships over the Euro-Mediterranean region, linear correlations are calculated between the monthly teleconnection indices for the five patterns and time series at each grid point of the monthly frequency of days with extreme precipitation, focusing on daily precipitation amounts that exceed a particular threshold value (a 90 % threshold is used). To evaluate dynamical processes, the teleconnection indices are also correlated with the frequencies of days with extreme values of dynamic tropopause pressure and precipitable water. The former quantity is used as a proxy for potential vorticity intrusions and the latter to identify regions of enhanced moisture. The results of this analysis indicates positive, statistically significant correlations between the NAO, AO, and SCAND indices and the frequency of extreme precipitation in the western Mediterranean; positive (negative) correlations between the EAWR index and the extreme precipitation frequency in the eastern (western) Mediterranean; and a positive correlation between the Niño3.4 index and the extreme precipitation frequency over the Iberian Peninsula and the Middle East. For all of the teleconnection patterns other than ENSO, the dynamic tropopause pressure correlation patterns resemble those for the precipitation. In contrast, similar precipitation and precipitable water correlation patterns are observed only for ENSO. These findings suggest that the teleconnections affect the interannual variation of the frequency of days with extreme precipitation over a large part of the Euro-Mediterranean region through their impact on the spatial distribution of regions withenhanced potential vorticity and air moisture. Simon O. Krichak & Joseph Barkan & Joseph S. Breitgand & Silvio Gualdi & Steven B. Feldstein The role of the export of tropical moisture into midlatitudes for extreme precipitation events in the Mediterranean regionTheor Appl Climatol, 121:499–515 DOI 10.1007/s00704-014-1244-6, 2015 Abstract The aims of the study are twofold: firstly, to investigate the role of the export of humid tropical air in the formation of cool season heavy precipitating events (HPEs) in the Mediterranean region (MR); and secondly, to examine the possible linkage between the export of humid tropical air and the multiyear trend in extreme precipitation in the region. For this purpose, we analyze the spatial distributions of a number of key atmospheric variables with a reanalysis data for more than 50 intense HPEs for the MR. The results of this evaluation for both individual and composite events suggest that the HPEs are associated with atmospheric rivers (ARs). The MR HPEs are being characterized by the poleward export of humid air of tropical origin into the midlatitude MR from the Atlantic Ocean and Arabian Sea. These export events appear to be associated with the effects of hurricanes or intense cyclones in the North Atlantic. It was also found that the linear trend (for 1979–2013) of the frequency of humid days (days with precipitable water greater than 20 kg m−2) is consistent with recent changes in the character of precipitation over the MR and southern Europe. Annarita Mariotti · Yutong Pan · Ning Zeng Andrea Alessandri Clim Dyn, 44:1437–1456, DOI 10.1007/s00382-015-2487-3, 2015. Abstract Long-term climate change and decadal variability in the Mediterranean region during 1860–2100 are investigated based on observational data and the newly available Coupled Model Intercomparison Project—Phase 5 (CMIP5) experiments. Observational records show that decadal variability and a general tendency for annual-mean conditions to be warmer and drier have characterized the Mediterranean during 1860–2005. Consistency with CMIP5 model simulations including greenhouse gases (GHG), as well as anthropogenic aerosols and natural forcings, suggest that forced changes have characterized aspects of Mediterranean climate during this period. Future GHG-forced change will take place in the midst of decadal variability, both internal and forced, as it has occurred in the past. However, future rates of forced warming and drying over the Mediterranean are projected to be higher than in the past century. The degree to which forced change and internal variability will matter depends on the climatic quantity being considered. For surface air temperature and Mediterranean Sea annual-mean evaporation and surface freshwater fluxes, variability and forced change have become comparable and the forced signal has already emerged from internal variability. For quantities with large internal variability and relatively small forced signal such as precipitation, forced change will emerge later on in the twenty-first century over selected regions and seasons. Regardless, the probability distribution of future precipitation anomalies is progressively shifting towards drier conditions. Overall, results highlight that both mean projected forced change and the variability that will accompany forced mean change should be considered in the development of future climate outlooks. Shira Raveh-Rubin and Heini Wernli Large-scale wind and precipitation extremes in the Mediterranean: a climatological analysis for 1979–2012Q. J. R. Meteorol. Soc. DOI:10.1002/qj.2531, 2015 A new method for identifying high impact large-scale wind and precipitation events in the extended Mediterranean region is outlined and applied to the European Centre for Medium-range Weather Forecasts (ECMWF) reanalysis dataset ERA-Interim for the years 1979–2012. The method highlights large-scale 10m gust and precipitation events that classify as extreme if integrated over a spatial scale of 1000 km and a temporal scale of 3 days. The method detects successfully high impact events, and reveals clear seasonal differences among the subregions of the Mediterranean. Western Mediterranean precipitation extremes are more intense, and occur mainly in autumn, while eastern Mediterranean events occur in winter. Composite dynamical analyses of large-scale wind and precipitation extremes, and a combination of them, highlight coherent dynamical flow structures associated with the extremes in the different subregions of the Mediterranean. Precipitation events are preceded by an upper-level trough and strong jet on its western flank, followed by cyclogenesis (mainly in the western Mediterranean), and/or amerging of the polar with the subtropical jet over northeastern Africa (in the eastern Mediterranean). Strong surface wind extremes develop around cyclones that intensify south of a deep parent cyclone near the exit of a strong anticyclonically curved jet, propagate eastwards and create a cold and dry northerly wind anomaly at the surface. Furthermore, combined large-scale wind and precipitation extremes often occur simultaneously near cyclones, either North Atlantic cyclones, which project the wind and precipitation into the western Mediterranean, or Mediterranean cyclones. The latter produce wind extremes over a localized area, which often overlaps entirely with the region that receives extreme Michiel Baatsen · Reindert J. Haarsma · Aarnout J. Van Delden · Hylke de Vries Severe Autumn storms in future Western Europe with a warmer Atlantic Ocean Clim Dyn 45:949–964DOI 10.1007/s00382-014-2329-8 2015 Abstract Simulations with a very high resolution (~25 km) global climate model indicate that more severe Autumn storms will impact Europe in a warmer future climate. The observed increase is mainly attributed to storms with a tropical origin, especially in the later part of the twenty first century. As their genesis region expands, tropical cyclones become more intense and their chances of reaching Europe increase. This paper investigates the properties and evolution of such storms and clarifies the future changes. The studied tropical cyclones feature a typical evolution of tropical development, extratropical transition and a re-intensification. A reduction of the transit area between regions of tropical and extratropical cyclogenesis increases the probability of reintensification. Many of the modelled storms exhibit hybrid properties in a considerable part of their life cycle during which they exhibit the hazards of both tropical and extratropical systems. In addition to tropical cyclones, other systems such as cold core extratropical storms mainly originating over the Gulf Stream region also increasingly impact Western Europe. Despite their different history, all of the studied storms have one striking similarity: they form a warm seclusion. The structure, intensity and frequency of storms in the present climate are compared to observations using the MERRA and IBTrACS datasets. Damaging winds associated with the occurrence of a sting jet are observed in a large fraction of the cyclones during their final stage. Baroclinic instability is of great importance for the (re-)intensification of the storms. Furthermore, so-called atmospheric rivers providing tropical air prove to be vital for the intensification through diabatic heating and will increase considerably in strength in the future, as will the associated flooding risks