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Many cyclone detection and tracking methods (CDTMs) have been developed in the past to study the climatology of extratropical cyclones. However, all CDTMs have different approaches in defining and tracking cyclone centers. This naturally leads to cyclone track climatologies of inconsistent physical characteristics. More than that, it is typical for CDTMs to produce a non-negligible amount of bogus tracks which can be perceived as “false positives”, or more generally as CDTM artifacts, i.e. tracks of weak atmospheric features that do not correspond to large or mesoscale vortices. Lack of consensus in CDTM outputs and the inclusion of significant amounts of bogus tracks therein, has long prohibited the production of a commonly accepted reference dataset of extratropical cyclone tracks. Such a dataset could allow comparable results on the analysis of storm track climatologies and could also contribute to the evaluation and improvement of CDTMs. To cover this gap, we present a new methodological approach that combines overlapping tracks from different CDTMs and produces composite tracks that concentrate the agreement of more than one CDTM. In this study we apply this methodology to the outputs of 10 well-established CDTMs which were originally applied to ERA5 reanalysis in the 42-year period of 1979–2020. We tested the sensitivity of our results to the spatio-temporal criteria that identify overlapping cyclone tracks, and for benchmarking reasons, we produced five reference datasets of subjectively tracked cyclones. Results show that climatological numbers of composite tracks are substantially lower than the ones of individual CDTM, while benchmarking scores remain high (i.e. counting the number of subjectively tracked cyclones captured by the composite tracks). This suggests that our method is able to filter out a large portion of bogus tracks. Indeed, our results show that composite tracks tend to describe more intense and longer-lasting cyclones with more distinguished early, mature and decay stages than the cyclone tracks produced by individual CDTMs. Ranking the composite tracks according to their confidence level (defined by the number of contributing CDTMs), it is shown that the higher the confidence level, the more intense and long-lasting cyclones are produced. Given the advantage of our methodology in producing cyclone tracks with physically meaningful, distinctive life stages and including a minimum number of bogus tracks, we propose composite tracks as reference datasets for climatological research in the Mediterranean. The supplementary material provides the composite Mediterranean tracks for all confidence levels and in the conclusion we discuss their adequate use for scientific research and applications.

The study deals with an intense rainstorm that hit the Middle East between 24 and 27 April 2018 and took the lives of 13 people, 10 of them on 26 April during the deadliest flash flood in Tzafit Basin (31.0∘ N, 35.3∘ E), the Negev Desert. The rainfall observed in the southern Negev was comparable to the long-term annual rainfall there, with intensities exceeding a 75-year return period. The timing of the storm, at the end of the rainy season when rain is relatively rare and spotty, raises the question of what the atmospheric conditions were that made this rainstorm one of the most severe late-spring storms. The synoptic background was an upper-level cut-off low that formed south of a blocking high which developed over eastern Europe. The cut-off low entered the Levant near 30∘ N latitude, slowed its movement from ∼10 to m s−1 and so extended the duration of the storm over the region. The dynamic potential of the cut-off low, as estimated by its curvature vorticity, was the largest among the 12 late-spring rainstorms that occurred during the last 33 years. The lower levels were dominated by a cyclone centred over north-western Saudi Arabia, producing north-westerly winds that advected moist air from the Mediterranean inland. During the approach of the storm, the atmosphere over Israel became unstable, with instability indices reaching values favourable for thunderstorms (e.g. CAPE>1500 J kg−1, LI=4 K) and the precipitable water reaching 30 mm. The latter is explained by lower-level moisture advection from the Mediterranean and an additional contribution of mid-level moist air transport entering the region from the east. Three major rain centres were active over Israel during 26 April, only one of them was orographic and the other two were triggered by instability and mesoscale cyclonic centres. The build-up of the instability is explained by a negative upper-level temperature anomaly over the region caused by a northerly flow east of a blocking high that dominated eastern Europe and ground warming during several hours under clear skies. The intensity of this storm is attributed to an amplification of a mid-latitude disturbance which produced a cut-off low with its implied high relative vorticity, low upper-level temperatures and slow progression. All these, combined with the contribution of moisture supply, led to intense moist convection that prevailed over the region for 3 successive days.

The Mediterranean Basin has several features that enhance cyclonic activity, such as its complex topography and sharp land-sea temperature differences. However, some processes occurring outside the basin can influence its seasonal variability. In this work, we highlight the relationship between the North Atlantic Storm Track (NAST) and cyclones passing through the Eastern Mediterranean (EM). We use Empirical Orthogonal Function (EOF) analysis of upper-level meridional wind variance to inspect monthly NAST regimes and their influence on wintertime flow in the EM.We find that the higher functions (EOF4-5) show stronger links to the region and specifically, to anomalies in synoptic fields associated with cyclones (upper-level potential vorticity, sea level pressure) and in monthly precipitation. These functions manifest as a pair of orthogonal zonal waves, reminiscent of subseasonal teleconnections that were previously linked to seasonal precipitation extremes in the EM (the South Levant pattern). It is hypothesized that this connection is mainly brought about by large-scale adiabatic advection of PV in the upper levels. Meanwhile, the two leading NAST modes (“pulsing” and latitudinal “shifting”) were found to produce a comparatively smaller effect.On the daily scale, we investigate the NAST-EM connection through the lens of zonally propagating Rossby wave packets, in both reanalysis and CMIP6 models (which capture the patterns well).

On January 8, 2020, an extreme storm event took place in the Eastern Mediterranean Sea, during which 100-130mm of rain fell in the northern part of Israel in one day. The heavy precipitation event resulted in seven deaths and damages to homes, vehicles, and infrastructure. At the same time, about 100km to the west of northern Israel, the sea was characterized by a mesoscale eddy with a warm core. In recent years, it was established that small-scale sea features affect the atmosphere above and synoptic-scale circulation patterns, including long-term rainfall. However, it is still unclear how these features may affect the propagation and intensity of individual storms, such as the January 8, 2020 storm event.Recently, the WRF (The Weather Research and Forecasting) atmospheric model was coupled with the ocean model MITgcm (MIT general circulation model). The coupled model was named the SKRIPS (Scripps–KAUST Regional Integrated Prediction System) model. The two SKRIPS model components (WRF and MITgcm) are well tested at high resolutions, and the regionality of the coupled model allows us to isolate local features while maintaining the large-scale circulation as observed.In this talk, I will present results from a high-resolution (~5km) coupled atmosphere-ocean regional simulation using the SKRIPS model performed during the January 8, 2020 event. The importance of the sea eddy in determining the storm intensity and propagation will be discussed, elaborating on the role of air-sea coupling and the model resolution. Understanding the effect of such small-scale sea features on extreme atmospheric events may improve their representation in weather and climate models, extending models prediction skill.

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 trend is found for the annual rainfall, reflecting a balance between a negative trend in the number of rainy days and a positive trend in the daily rainfall intensity, both on the order of 2.0%/decade. In the mid-winter, the rainfall and the daily intensity increased, while both declined 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, shortened by 7 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. The contraction of the rainy season and the increase in the daily intensity have far-reaching environmental impacts in this vulnerable region.

The Red-Sea Trough (RST) is a lower-level trough extending from the tropical low-pressure to the Levant. Its annual occurrence is 20%, between October and May, producing mostly dry weather, but occasionally active and causing local showers and floods. During winter the dominant synoptic system over the Levant is the Cyprus low (CL). Previous studies showed that some CLs form within pre-existing RSTs, through a tropical-extratropical interaction.This study is the first comprehensive climatological framework of such formation events, analyzing occurrence, seasonality and the resulting rainfall in Israel. The study looked at events of new CLs formed within the domain 31°-35°N, 30°-36°E while a RST was detected within 24 hours before the event. We used the 6-hourly ERA-Interim database, with 0.75°×0.75° resolution, during 1979-2017, and identified 104 formation events, which constitute 10% of the CLs. Most events occurred during fall and early winter, as the case for the RST. Eighty-four percent of them formed during the evening or the night, and almost two thirds of the CLs disappeared temporarily at noon and regenerated afterwards. This is attributed to the sea/land diurnal oscillation. Most of the CLs that formed were found shallow with little rain, but occasionally became major storms, like "Alexa", which caused extreme snowing in Jerusalem, in December 2013.The evolution scenarios leading to formation events were divided into four clusters, according to the synoptic situation at the 500-hPa geopotential height. The first one is characterized by a closed cyclone approaching from the southwest, often connected to active RSTs, such as the event that occurred in 2-4 November 1994. In the second, a trough is deepening from the northern sector, possibly a polar intrusion, like the "Alexa" storm. In the third, the most populated cluster, a trough is approaching from the west. A separate cluster contains four events with no upper-level support.

Previous observation analyses have shown a declining rainfall trend over Israel, mostly statistically insignificant. These findings support the projections of the climatic models for the 21th century. The current study, for the period 1975-2020, undermines these findings, and the alarming future projections, and elaborates changes in the distribution of the rain along the rainy season.The annual rainfall has a negligible trend, of +0.002%/decade, the number of rainy days has declined by -1.9%/decade and the average daily rainfall has increased by +2.1%/decade, all statistically insignificant. In the mid-winter both rainfall and daily rain intensity increased, while these variables have declined in the autumn and spring. The implied contraction of the rainy season is estimated by 2 measures. The 'effective length', which is determined by the time between accumulation of 10% and 90% of the annual rainfall, lasting 112 days on the average. This has been shortened by seven days during the study period. The other is the Seasonality Index (SI), reflecting the temporal concentration of the rainy season around its center. The trend found indicates that the regional climate is shifting from being between 'Markedly seasonal with a long dry season' and 'Most rain in ≤3 months', further toward the latter.The trend in Cyprus Low occurrence and in the Mediterranean Oscillation Index were found to explain the rainfall trends only partially. We suggest that the cause for the increase in the mid-winter rain intensity is the increase in sea-surface temperature, found over the east Mediterranean, and for the decline in the transition seasons, to the poleward expansion of the subtropical highs. The contraction of the rainy season on the one hand, and the increased daily rain intensity in the mid-winter on the other, have ecological and hydrological impacts in this vulnerable region.

The study deals with an intense rainstorm that hit the Middle–East between 24 and 27 April 2018. The storm reached its peak over Israel in April 26, when it produced a heavy flash flood that took the lives of ten people. The rainfall observed in the southern Negev was comparable to the long-term annual rainfall there. The timing of the storm is also unique, at the end of the rainy season when rain is relatively rare and spotty. The study analyzes the dynamic and thermodynamic conditions that made this rainstorm one of the latest spring severe events in the region during the last 3 decades. The synoptic background was an upper-level cut-off low that entered the region from west, along 30° N latitude, which is rather exceptional for such systems in the late spring. While approaching the Levant, it slowed its movement from ~ 10 to −1. On the day of maximum intensity, the radius of the cyclone shrank to 275 km. The effect of the small radius was estimated by the measure of its curvature vorticity (MCV), which was the largest among the spring rainstorms during the latest 33 years. The lower-levels were dominated by a northwesterly wind that advected moist air from the Mediterranean inland. During the approach of the storm, the atmosphere over Israel became unstable, with instability indices reaching values favorable for thunderstorms (CAPE = 909 J Kg−1, LI = −4.9 K, SI = −2.7 K and MKI = 30 K), and the precipitable water increased from 17 to 30 mm. The latter is explained here by a combined effect of the lower-level moisture advection and a mid-level band of tropical moisture that entered Israel above it. Three major rain centers were active during April 26, two of them were non-orographic, which is unusual for this type of system. This is explained by the dominance of sub-synoptic features, found in the 0.25 resolution data of ERA5 that were used to derive Omega and MKI maps. The buildup of static instability is explained by a −5 K temperature anomaly over the region, caused by a northerly flow east of the blocking high over North Europe that transported cold air over the Mediterranean water. The unique intensity of this storm is attributed to an amplification of a mid-latitude disturbance, which produced a cut-off low, with its implied high relative vorticity, low upper-level temperatures, and slow progression. All these, combined with the contribution of several moisture sources, led to extreme dynamic and thermodynamic conditions favorable for this exceptionally severe rain-storm.

Superbolts are defined as lightning flashes that are a thousand times stronger than normal ones, and their occurrence is estimated to be less than 0.001% of total number of lightning on earth. The global distribution of these extremely powerful lightning flashes is remarkably different than that of regular lightning, which are concentrated in the well-known convective "chimneys" in tropical Africa, South-America and the maritime continent in South-East Asia. The physical mechanisms producing these powerful flashes remain unknown, and the puzzle is exacerbated by the fact that they are discovered mostly over oceans, in maritime winter storms.The Mediterranean Sea is one of the most prolific regions where super-bolts occur, especially in the months November-January (Holzworth et al., 2019). We analyzed 8 years of lightning data obtained from the Israeli Lightning Detection Network (ILDN), defining a 200kA peak current threshold for superbolts. We mapped the spatial and temporal distribution of superbolts and their monthly frequency in winter season thunderstorms (DJF) in the eastern Mediterranean, and identified the meteorological and microphysical circumstances in such storms.Our working hypothesis is that large amounts of desert dust aerosols, coming from the Sahara Desert, are ingested into maritime winter storms over the eastern Mediterranean. The large dust contributes to convective invigoration, enhanced freezing and efficient charge separation, implying that superbolts are more likely to occur in the presence of large dust. We will present the results of simulation conducted using the WRF-ELEC numerical model, and WRF with spectral bin microphysics coupled with Lynn et al.'s (2012) Dynamic Lightning Scheme (DLS) and the Lightning Potential Index (Yair et al., 2010; LPI), for selected case studies when an enhanced fraction of superbolts was observed. Holzworth, R. H., McCarthy, M. P., Brundell, J. B., Jacobson, A. R., and Rodger, C. J. (2019). Global distribution of superbolts. J. Geophys. Res. Atmos., 124., doi:10.1029/2019JD030975.Lynn, B., Y. Yair, C. Price, G. Kelman and A. J. Clark (2012). Predicting cloud-to-ground and intracloud lightning in weather forecast models. Weather and Forecasting, 27, 1470-1488, doi:10.1175/WAF-D-11-00144.1.Yair, Y., B. Lynn, C. Price, V. Kotroni, K. Lagouvardos, E. Morin, A. Mugnai, and M. d. C. Llasat (2010). Predicting the potential for lightning activity in Mediterranean storms based on the Weather Research and Forecasting (WRF) model dynamic and microphysical fields, J. Geophys. Res., 115, D04205, doi:10.1029/2008JD010868

The dissolution of transition metal ions from positive electrodes and loss of (both electroactive and transport) Li+ ions seriously impair the durability of lithium ion batteries. We show herein that the improvement in the cycle life of lithium manganate spinel-graphite cells effected by multifunctional separators results from smaller interfacial resistances at both positive and negative electrodes, that can in turn be traced back to thinner, more uniform, and chemically different surface films, due to lessened parasitic reactions and a decreased accumulation of parasitic reaction products at electrode surfaces, as evidenced by HR-SEM, FIB-SEM, EDX, 19F MAS NMR, and ICP-OES data.

We report new electrical measurements conducted during the massive dust outbreak that occurred over the Levant in September 08–12, 2015. That event was one of the strongest dust storms on record and engulfed the entire region for 5 consecutive days, over Iraq through Syria, Jordan, Israel, Lebanon, Cyprus and Egypt. At its peak, Aerosol Optical Thickness of 4.0 was measured in southern Israel. Ground-based measurements of the electrical field (Ez) and current density (J) were conducted at the Wise Observatory (WO) in Mizpe-Ramon (30°35′N, 34°45′E) and near the top of Mt. Hermon (30°24′N, 35°51′E). During the dust outbreak very large fluctuations in the electrical parameters were measured at both stations, with remarkable differences between the two locations. While at the Mt. Hermon station we registered positive values of the electric field and total current density, the values registered at the Wise Observatory were significantly smaller and more negative. The Mt. Hermon site showed Ez and J values fluctuating between − 460 and + 570 V m− 1 and − 14.5 and + 18 pA m− 2 respectively. In contrast, the Ez values registered at WO varied between − 430 and + 10 V m− 1, and the current density fluctuated between − 6 and + 3 pA m− 2. We show that the unique generation and evolution of this dust outbreak gave rise to a significantly different charge structure compared with that observed in short lived convective events, and suggest a tentative explanation for the obtained results.

Autocatalytic decomposition of LiPF6, with generation of HF and Lewis acids is the root cause for Li-ion battery (LIB) performance degradation. Acidic species promote various parasitic reactions, among which transition metal ions’ dissolution and the loss of electroactive as well as transport Li+ have the most detrimental consequences for LIB performance. Herein we report on the performance improvements enabled by an acid-scavenging separator in cells with graphite negative and LiMn2O4 or LiNi0.6Mn0.2Co0.2O2 positive electrodes. After 4 weeks of cycling at 55 °C, LiMn2O4∥graphite and LiNi0.6Mn0.2Co0.2O2∥graphite cells with functional separators retain 100 and 43% more capacity, respectively, than cells with plain polypropylene separators. Furthermore, cells with functionalized separators have half of the interfacial impedances of cells with baseline separators, irrespective of positive electrode. The benefits afforded by acid-scavenging separators thus extend to broader classes of cell chemistries, beyond...

The Levant region is dominated in the summer by the persistent Persian Trough. Thus, the current synoptic classifications lack the ability to reflect inter-diurnal variations in the local weather conditions. This study aims to overcome this weakness and has two objectives: to develop operative prediction equations for the local weather conditions based on synoptic-scale data, and to propose a new synoptic classification, based on the environment to climate approach, to better reflect the local climatic stress. Prediction equations were derived for the national heat-stress (NHS) and the height of the persistent marine inversion (inversion base, IB). The potential predictors are comprised of atmospheric variables found correlated with these weather attributes together with indices representing synoptic to large-scale features. The indices were derived through a composite maps analysis of days with extreme values of these attributes. The Climatic Stress Index (CSI) developed is a combination of the heat-stress and the inversion height, for which a separate prediction equation was derived. The spectrum of the calculated daily CSI values was divided into three parts of equal size, used as the basis of the new synoptic types, defined as: ‘comfort’, ‘medium’, and ‘discomfort’. The attribution of a certain day to one of these types is determined according to its calculated CSI. Our proposed classification was found to better delineate the NHS and the height of the IB in Israel. The downscaling schemes and the new synoptic classification are applicable for both operative weather prediction and climate prediction. The latter enables the assessment of future trends in the climatic stress, in general, and heat-stress, in particular. This is due to being compatible with the output of operative weather prediction models as well as for the format of the disseminated output of climate models.

Manganese dissolution from positive electrodes seriously reduces the useful life of Li-ion batteries, especially with positive electrode materials having spinel phases. We show herein that Mn ion trapping separators containing inexpensive mass-produced materials may dramatically increase the life of Li-ion batteries. LiMn2O4-graphite cells containing these materials and a LiPF6 based electrolyte solution display excellent capacity retention during cycling at both room and elevated temperatures, over baseline cells with plain separators. After 30 days of cycling at 55 °C and C/5 rate, LiMn2O4-graphite cells containing three different Mn-trapping materials with nitrogen functionalities retain between 75% and 125% more of the initial capacity than the baseline cells. Mn amounts in graphite negative electrodes from cells with the functional separators are 13–21 times lower than in baseline cells. LiMn2O4 lattice shrinkage in cells with functionalized separators is negligible compared to baseline cells, indicating major reductions in the loss of electrochemically active Li+ ions and increased stability of the LiMn2O4 crystal lattice.

The addition of single-wall carbon nanotubes (SWCNT) to lead-acid battery electrodes is the most efficient suppresser of uncontrolled sulfation processes. Due to the cost of SWCNT, we studied the optimization loading of SWCNT in lead-acid battery electrodes. We optimized the SWCNT loading concentrations in both the positive and negative plates, separately. Loadings of 0.01% and 0.001% in the positive and negative active masses were studied, respectively. Two volts of lead-acid laboratory cells with sulfuric acid, containing silica gel-type electrolytes, were cycled in a 25% and 50% depth-of-discharge (DOD) cycling with a charging rate of C and 2C, respectively, and discharge rates of C/2 and C, respectively. All tests successfully demonstrated an excellent service life up to about 1700 and 1400 cycles for 25% and 50% DOD operations, respectively, at a low loading level of SWCNT. This performance was compared with CNT-free cells and cells with a multiwall carbon nanotube (MWCNT) additive. The outstanding performance of the lead-acid cells with the SWCNT additive is due to the oxidative stability of the positive plates during charging and the efficient reduction in sulfation in both plates while forming conducting active-material matrices.

תקציר בעברית: העולם מתחמם בהתמדה. ההתחממות מלווה בשינויים במשטר הרוחות והגשמים, מאז אמצע שנות ה –70 שחלק מהם מלווים באירועים קיצוניים, המהווים סכנה לטבע, לאדם ולרכושו. התחממות תגרום ישירות להתרבות גלי חום ולהתארכותם, ולעלייה בעומס החום על החי והצומח, ולכן מהווה סכנה מוחשית עבור האדם. גלי החום הממושכים יגבירו את סכנת השרפות ואת זיהום האוויר הנגרם מהן, שמביא כבר כיום לתמותה נרחבת. התחממות האוקיינוסים גורמת להתפשטות המים, וזו בתוספת זרימת מים ליותר מחצי מקרחוני היבשה המפשירים גורמות שתיהן לעליית פני הים, שתגיע עד לסוף המאה ה–21 מטר. יש סכנת הצפה לחופים שטוחים, ומתקני חוף עלולים להיפגע. עוצמת הגשמים צפויה לעלות ולגרום להחרפה בסכנת השיטפונות. באזורים מסוימים (כגון האזורים הטרופיים) תחול עלייה בכמות המשקעים הכוללת, ובאחרים (למשל באזורים בעלי אקלים ים תיכוני) תתרחש ירידה. תופעות מסוימות, כגון סופות טרופיות, צפויות להחמיר עקב ההתחממות, אך טרם החמירו. תופעות אחרות, כגון גלי קור, מחמירות, אך לא ברור אם הדבר קשור בהכרח להתחממות העולמית וכיצד. במאמר זה אסקור תופעות משני הסוגים, אציג את הטיעונים לגביהן ואת עמדתי. בישראל מורגשות כבר כעת התחממות והתייבשות, ויש לצפות שגלי החום ייעשו כבדים וארוכים יותר, שעונת הגשמים תתקצר ושההפוגות שבין אירועי הגשם יתארכו. הואיל וההתחממות מגבירה את ההתאדות מפני הקרקע, תידרש החקלאות המקומית לתוספת השקיה ולהיערכות מוגברת מפני שרפות. בו–בזמן, יש להיערך לשיטפונות קשים יותר ולאירועי שלג כבד באזורים ההרריים.

We report on atmospheric electrical measurements conducted at the Wise Observatory in Mitzpe-Ramon, Israel (30°35′N, 34°45′E) during a large dust storm that occurred over the Eastern Mediterranean region on 10–11 February 2015. The dust was transported from the Sahara, Egypt and the Sinai Peninsula ahead of an approaching Cyprus low. Satellite images show the dust plume covering the Negev desert and Southern Israel and moving north. The concentrations of PM10 particles measured by the air-quality monitoring network of the Israeli Ministry of the Environment in Beer-Sheba reached values > 450 μg m − 3 and the AOT from the AERONET station in Sde-Boker was 1.5 on February 10th. The gradual intensification of the event reached peak concentrations on February 11th of over 1200 μg m − 3 and an AOT of 1.8. Continuous measurements of the fair weather vertical electric field (Ez) and vertical current density (Jz) were conducted at the Wise Observatory with 1 minute temporal resolution. Meteorological data was also recorded at the site. As the dust was advected over the observatory, very large fluctuations in the electrical parameters were registered. From the onset of the dust storm, the Ez values changed between + 1000 and + 8000 V m − 1 while the current density fluctuated between − 10 pA m 2 and + 20 pA m 2 , both on time-scales of a few minutes. These values are significant departures from the average fair-weather values measured at the site, which are ~− 200 V m − 1 and ~ 2 pA m 2 . The disturbed episodes lasted for several hours on February 10th and the 11th and coincided with local meteorological conditions related to the wind speed and direction, which carried large amounts of dust particles over our observation station. We interpret the rapid changes as caused by the transport of electrically charged dust, carrying an excess of negative charge at lower altitudes.

This work evaluates two numerical warning indicators of severe weather. These indicators, the MKI and RDI indices, were developed within the framework of the EU-funded FLASH project which studies flash flood events in the Mediterranean Basin. The MKI (Modified K-Index) is a modification of the K-Index, which expresses probability of lightning activity, and the RDI (Rain Dynamical Index) is the integrated upward moisture flux. The indices were tested on 59 episodes which occurred during nine rainstorms in Israel, Greece, Spain, Italy, and Cyprus. The data for calculation of the indices included rain cell identification derived from microwave radiometer imagery of polar orbiting NOAA satellites, rain RADAR data, and lightning activity from the international ZEUS detection system. Atmospheric data with 0.5° × 0.5° spatial resolution and 6-h time resolution were used for the calculation and the display of the two indices. The indices were tested by calculating the spatially correlating locations with high index values and actual locations of intense rain and intense lightning. The RDI detected both event types: rain and lightning, with a statistically significant success rate and a low rate of false results. The MKI was successful in indicating intense lightning activity, but the rate of correct indications was not statistically significant and there was a high rate of false indications. The results suggest that the RDI computed with output of weather prediction models is a potentially good predictor of torrential rain and therefore can predict flash floods caused by such rain in the Mediterranean region.

This article presents a semi-objective methodology to classify formation scenarios of a new ‘daughter’ cyclone (DC), based on the thermal field characteristics of the parent cyclone (PC). An automated algorithm assigns a DC to one of seven formation types, according to the following considerations: Whether the DC is formed on a front belonging to the parent's frontal system or to a different frontal system, and whether this frontal system is cold, warm or quasi-stationary. An additional type contains DCs formed within the warm sector of the parent. The algorithm uses measures derived from wind and temperature fields at 850-hPa: the temperature gradient, the temperature advection and the temperature Laplacian, each computed at the formation location of the DC, and also the temperature difference between the DC and the PC. The classification method was applied to 4303 Mediterranean DCs which were observed during 33 winters. Totally 85% of the DCs were identified as belonging to one of the seven predefined types, implying that the formation of the remaining 15% was not related to baroclinic or thermal factors. Among the successfully classified DCs, over half were formed on the frontal system of the parent, a third of the DCs on a separate frontal system and only 13% were formed within the warm sector. Most of the ‘cold front’ cyclones were formed at the major Mountain Lee locations, whereas those formed on warm fronts were generated mostly over the Adriatic, Ligurian and Aegean Seas. Inspection of composite maps of distinct formation types in various regions revealed unique formation scenarios, like DCs forming over western Morocco but belonging to third generation Genoa Lows. Other reflects discontinuous movement of cyclones, resulting from encounter with topographical obstacles, found mostly on PCs' warm fronts, or from the attraction of cyclogenetic areas left behind, mostly on PCs' cold fronts.

Manganese dissolution from positive electrodes significantly reduces the durability of lithium-ion batteries. Knowledge of dissolution rates and oxidation states of manganese ions is essential for designing effective mitigation measures for this problem. We show that electron paramagnetic resonance (EPR) combined with atomic absorption spectroscopy (AAS) or inductively coupled plasma (ICP) can determine both manganese dissolution rates and relative Mn(3+) amounts, by comparing the correlation between EPR and AAS/ICP data for Mn(2+) standards with that for samples containing manganese cations dissolved from active materials (LiMn2O4 (LMO) and LiNi(0.5)Mn(1.5)O4 (LNMO)) into the same electrolyte solution. We show that Mn(3+), and not Mn(2+), is the dominant species dissolved from LMO, while Mn(2+) is predominant for LNMO. Although the dissolution rate of LMO varies significantly for the two investigated materials, due to particle morphology and the presence of Cr in one of them, the Mn speciation appears independent of such details. Thus, the relative abundance of dissolved manganese ions in various oxidation states depends mainly on the overall chemical identity of the active material (LMO vs LNMO). We demonstrate the relevance of our methodology for practical batteries with data for graphite-LMO cells after high-temperature cycling or stand at 4.2 V.

Relatively high concentrations of particulate matter (PM) are characteristic to Israel and the Middle East. This is mostly attributed to natural dust storms and partly to anthropogenic sources, local, or remote. The research deals with relations between concentrations of PM10 and PM2.5, and between synoptic conditions and regional climatic stress. Our particular focus is the summer, a season with no dust outbreaks when mostly one synoptic system, the Persian Trough prevails over the region, with associated northwesterly Etesian winds. Therefore, the “climate to environment” approach to distinguishing among PM concentrations by classes of synoptic systems is not very successful in the summer. In contrast, the climatic stress index (CSI), representing the “environment to climate” approach, was found positively correlated with PM concentrations in Haifa, Israel, and more effective in explaining inter-diurnal variations of PM pollution. Synoptic analysis performed through composite anomaly maps for days with higher and lower PM concentration, indicates a weakening of the Etesian winds in days with high CSI. On the one hand, the weaker winds reduce imported PM, but, on the other hand, the lower marine inversion in days with high CSI enhances PM pollution from local sources, by weakening the dispersion mechanisms, both vertical and horizontal. The higher level of PM pollution in days with high CSI indicates dominance of the local PM sources. The positive correlation between climatic stress and PM pollution, and increased climatic stress associated with global and regional warming, necessitate further tightening of control on anthropogenic pollution sources.

The Mediterranean is one of the most cyclogenetic regions in the world. The cyclones are concentrated along its northern coasts and their tracks are oriented more or less west-east, with several secondary tracks connecting them to Europe and to North Africa. The aim of this study is to examine scenarios in the development of Mediterranean cyclones, based on five selected winter seasons (October–March). We detected the cyclones subjectively using 6-hourly Sea-Level Pressure maps, based on the NCAR/NCEP reanalysis archive. HMSO (1962) has shown that most Mediterranean cyclones (58%) enter the Mediterranean from the Atlantic Ocean (through Biscay and Gibraltar), and from the south-west, the Sahara Desert, while the rest are formed in the Mediterranean Basin itself. Our study revealed that only 13% of the cyclones entered the Mediterranean, while 87% were generated in the Mediterranean Basin. The entering cyclones originate in three different regions: the Sahara Desert (6%), the Atlantic Ocean (4%), and Western Europe (3%). The cyclones formed within the Mediterranean Basin were found to generate under the influence of external cyclonic systems, i.e. as "daughter cyclones" to "parent cyclones" or troughs. These parent systems are located in three regions: Europe (61%), North Africa and the Red Sea (34.5%) and the Mediterranean Basin itself (4.5%). The study presents scenarios in the development of Mediterranean cyclones during the winter season, emphasizing the cyclogenesis under the influence of various external forcing. The large difference with respect to the findings of HMSO (1962) is partly explained by the dominance of spring cyclones generating in the Sahara Desert, especially in April and May that were not included in our study period.

Addition of various carbon materials into lead-acid battery electrodes was studied and examined in order to enhance the power density, improve cycle life and stability of both negative and positive electrodes in lead acid batteries. High electrical-conductivity, high-aspect ratio, good mechanical properties and chemical stability of multi-wall carbon nanotubes (MWCNT, unmodified and mofified with carboxylic groups) position them as viable additives to enhance the electrodes' electrical conductivity, to mitigate the well-known sulfation failure mechanism and improve the physical integration of the electrodes. In this study, we investigated the incorporation-effect of carbon nanotubes (CNT) to the positive and the negative active materials in lead-acid battery prototypes in a configuration of flooded cells, as well as gelled cells. The cells were tested at 25% and 30% depth-of-discharge (DOD). The positive effect of the carbon nanotubes (CNT) utilization as additives to both positive and negative electrodes of lead-acid batteries was clearly demonstrated and is explained herein based on microscopic studies.

Summary The relationships between the evaporation from a medium size (168.7 km 2 ) Lake Kinneret (Northern Israel), and its governing synoptic factors are well demonstrated during the summer of 2010. During July–August the daily temperature of the air and water surface were ∼2–4 °C higher, the daily wind over the lake was ∼80% weaker, and the evaporation from the lake was ∼5% lower than the long-term July–August mean. In this study, we explore the impact of the regional and local synoptic-scale atmospheric conditions on the evaporation from the lake during exceptionally hot days in the mid-summer months (July–August). The factors that were found to be correlated with the lake evaporation are the temperatures at 850 hPa (negative) and 500 hPa (positive), the sea level pressure difference between Northern Egypt and Armenia (positive), and the height of the marine inversion (positive). Synoptic analysis indicates that two conditions are responsible for the reduction of the Mediterranean Sea Breeze (MSB) during exceptionally hot days, and consequently to the reduction of evaporation from the lake. First, the weakening of the permanent synoptic Etesian winds, which otherwise supports the inland penetration of the MSB; and second, the descent of the marine inversion to a height below the topographic ridge of the Galilee Mountains upwind of the study area, which blocks the Marine Sea Breeze from reaching Lake Kinneret.

This study is the first one to objectively identify ‘parent–daughter’ relationships between cyclones and to apply it to Mediterranean cyclones (MCs). The methodology includes cyclone detection, tracking and mapping the area of influence of a cyclone; here daughter cyclones are expected to be found. Cyclone detection and tracking is based on standard algorithms, which were modified to cope with irregularities in intensity and trajectory shapes of MCs. We have developed our own algorithm for mapping cyclones' area of influence. Application of our methodology to the ERA-Interim data for 33 mid-winter seasons identified parents for 97.5% of the MCs. While previous studies claimed that most MC parents are situated over Europe, this study found the majority of MCs' parents (56%) positioned over the Mediterranean itself. This disagreement stems from the fine spatial resolution used here (0.75° × 0.75°), which enabled uncovering smaller cyclones than noticed previously, thus revealing earlier stages of cyclogenesis. The parenthood analysis identified two main types of cyclogenesis within the Mediterranean; one driven by parent MCs, the other driven by Atlantic or European cyclones. The latter is manifested either by directly generating a new MC or by intensifying existing weak MCs. Cyclone generations were explored through backtracking chains of parents down to the ninth generation, the longest chain found. The results indicate that the primary source of MCs is the Atlantic (2/3 of the MCs) and then Equatorial Africa and the Red Sea (1/3). The results also imply that although native MCs owe their existence to the Atlantic-European cyclone track, regional cyclogenetic effects, such as topographic, thermal and baroclinic, are even more influential. The innovative methodology for objective identification of cyclone parents can be used to characterize cyclogenetic scenarios, in particular away from main storm tracks and over complex terrain.

We demonstrate herein that Mn3+ and not Mn2+, as commonly accepted, is the dominant dissolved manganese cation in LiPF6-based electrolyte solutions of Li-ion batteries with lithium manganate spinel positive and graphite negative electrodes chemistry. The Mn3+ fractions in solution, derived from a combined analysis of electron paramagnetic resonance and inductively coupled plasma spectroscopy data, are ∼80% for either fully discharged (3.0 V hold) or fully charged (4.2 V hold) cells, and ∼60% for galvanostatically cycled cells. These findings agree with the average oxidation state of dissolved Mn ions determined from X-ray absorption near-edge spectroscopy data, as verified through a speciation diagram analysis. We also show that the fractions of Mn3+ in the aprotic nonaqueous electrolyte solution are constant over the duration of our experiments and that disproportionation of Mn3+ occurs at a very slow rate.

Prolonged dry spells (PDSs) during the rainy season have severe environmental implications, including water shortage, damage to agriculture and increased potential for forest fires. This holds in particular for vulnerable regions, such as the Levant, already subjected to decrease in rainfall and lengthening of dry spells, in agreement with predictions of climatic models for the coming decades. This is the first comprehensive study which identifies atmospheric patterns responsible for PDS occurrence on thousands of kilometres scale. A total of 178 PDSs, of >7 days, were found within the 62 seasons studied. A subjective inspection of upper-level geopotential height (GPH), sea-level pressure (SLP) and lower-level temperature anomalies point at three types, each associated with a definite climatic regime. The ‘subtropical’ type is associated with an expansion of the subtropical high over the majority of the Mediterranean, accompanied by northward migration of the Mediterranean cyclone track. The ‘baroclinic’, the most frequent type, is induced by a pronounced stagnant ridge over the eastern Mediterranean, being a part of Rossby wave, accompanied by a pronounced trough/cut-off low over the western Mediterranean. The ‘polar’ type results from intrusion of lower-level continental polar air associated with upper-level trough east of the Levant and blocking high over central Europe. Quantitative indices were derived for objective classification of the types, based on the climatic regimes defined subjectively, and the centers of action representing each. Composite maps for each type indicate substantial differences in the synoptic configuration and the factors explaining absence of rain. For the subtropical type, the dynamic factor of subsidence is dominant. For the polar, the thermodynamic factor of continental dry advection is dominant and for the baroclinic, both dynamic and thermodynamic factors are important. Classification of PDSs according to synoptic scenarios enables analysis of future changes in the occurrence and duration pattern of PDSs, using output of climate models.

Cloud-to-ground lightning flashes usually consist of one or several strokes coming in very short temporal succession and close spatial proximity. The common method for converting stroke data into flashes is using the National Lightning Detection Network (NALDN) thresholds of maximum temporal separation of 0.5 s and maximum lateral distance of 10 km radius between successive strokes. In the present study, we tested a location-based algorithm with several spatial and temporal ranges, and analyzed stroke data obtained by the Israel Lightning Location System (ILLS) during one year (1 August 2009–31 July 2010). We computed the multiplicity, the percentage of single stroke flashes and the geographical distribution of single vs. multiple-stroke flashes for thunderstorms in the Eastern Mediterranean region. Results show that for the NALDN thresholds, the percentage of single stroke flashes in Israel was 37% and the average multiplicity was 1.7. We re-analyzed the data with a spatial range that equals twice the ILLS location error and shorter times. For the new thresholds of maximum distance of 2.5 km and maximum allowed temporal separation of 0.2 s we find that the mean multiplicity of negative CGs is lowered to 1.4 and find a percentage of 58% of single stroke flashes. A unique severe storm from 30 October 2009 is analyzed and compared to the annual average of 2009/10, showing that large deviations from the mean values can occur in specific events.

Investigation of the failure mechanisms of Li-ion batteries and the consequences of their failure is of vital importance to the design of durable batteries. In this work, we examined the electrochemical performance of half and full Li-ion battery cells with several cathode materials including LiMn0.8Fe0.2PO4 (LMFP), LiNi0.5Mn1.5O4 (LMNO), and Li[LixNiyCozMn1−x−y−z]O2 Li-rich layered oxides (HC-MNC). In contrast to half cells which demonstrated good cycling performance with more than 90% of their initial capacities retained after 100 cycles, the full cells exhibited severe capacity loss. Based on postmortem analyzes of electrodes from cells cycled at 30 and 60◦C, using electrochemical, spectroscopic, and microscopic techniques, we conclude that the loss of active lithium ions due to parasitic side reactions is a main reason for capacity fading of Li-ion battery full cells. Structural degradation of the electrodes during cycling is at best a second order effect. © 2014 The Electrochemical Society. [DOI: 10.1149/2.0731410jes] All rights reserved.

During July–August 2011, Expedition 28/29 JAXA astronaut Satoshi Furukawa conducted TLE observations from the International Space Station in conjunction with the “Cosmic Shore” program produced by NHK. An EMCCD normal video-rate color TV camera was used to conduct directed observations from the Earth-pointing Cupola module. The target selection was based on the methodology developed for the MEIDEX sprite campaign on board the space shuttle Columbia in January 2003 ( Ziv et al., 2004 ). The observation geometry was pre-determined and uploaded daily to the ISS with pointing options to limb, oblique or nadir, based on the predicted location of the storm with regards to the ISS. The pointing angle was rotated in real-time according to visual eyesight by the astronaut. We present results of 10 confirmed TLEs: 8 sprites, 1 sprite halo and 1 gigantic jet, out of

[1] The study examines the δ18O of rain observed in the middle of the Negev Desert, Israel, based on seven rainstorms, associated with convective clouds resulting from midlatitude cyclones found over Trans-Jordan. The analysis is based on synoptic maps, vertical atmospheric cross sections, and air back trajectories. The rainwater sampling was done in temporal scale of hours. Four known factors were addressed here: the temperature effect, the amount effect, and two geographical effects: the marine and continental effects. The temperature effect is expressed by a positive relation between the lower level temperature and the isotopic composition. The amount effect, related to rainfall, is negative. The marine effect, expressed by a relation between the time the rain-producing air spends above the Mediterranean Sea, is positive and the continental effect, associated with the passage over land is negative. The linear relationships found in this study met the expectations, although only the amount effect was statistically significant. A fifth effect, entitled cloud top effect proposed here, relates to the height of the convective cloud layer top. It assumes that lower top prevents entrainment of upper cold air into the clouds, so the isotopic composition is enriched. The cloud top effect was found most statistically significant.

This research analyses the scenarios that break the monotonic summer regime over the East Mediterranean (EM). The study compares the five upper, median and lower percentiles of the 850-hPa temperature for July–August 1975–2005. The temperature differences were found to be confined to the lower 4 km. They are controlled by the intensity of the negative temperature advection, but not by the prevailing subsidence. Air trajectory analysis shows that the regional prevailing northwest winds are the strongest prior to cool events and the weakest, or nonexistent, prior to hot events. An index representing the location of the air source is proposed as an effective predictor for the temperature. The hot and the cool days were subdivided according to their evolution scenarios. All the cool days were associated with deepening of upper troughs over the EM. Different scenarios were found to generate hot days; ‘tropical’, associated with intrusion of tropical-like air, ‘subtropical’, resulting from an expansion of the subtropical high from North Africa towards the EM, and ‘baroclinic’, associated with a pronounced upper-level ridge, part of a Rossby wave over the Mediterranean Basin. The ‘tropical’ scenario was well identified through the mid-level relative humidity. An alternative classification approach, the objective K-Means clustering method, was applied to the air back-trajectories reaching the EM. They isolated successfully only the ‘tropical’ type. Back-tracking of temperature anomalies indicate two different evolutions for the hot days; one is associated with propagation from the west sector and other is quasi-stationary, associated with intrusion of tropical air. The cool events are all propagating from northwest. This indicates that extreme summer events over the EM are mostly regulated by mid-latitudes disturbances travelling eastward rather than by the Asian Monsoon.

The study aims to evaluate the ability of global, coupled climate models to reproduce the synoptic regime of the Mediterranean Basin. The output of simulations of the 9 models included in the IPCC CMIP3 effort is compared to the NCEP-NCAR reanalyzed data for the period 1961–1990. The study examined the spatial distribution of cyclone occurrence, the mean Mediterranean upper- and lower-level troughs, the inter-annual variation and trend in the occurrence of the Mediterranean cyclones, and the main large-scale circulation patterns, represented by rotated EOFs of 500 hPa and sea level pressure. The models reproduce successfully the two maxima in cyclone density in the Mediterranean and their locations, the location of the average upper- and lower-level troughs, the relative inter-annual variation in cyclone occurrences and the structure of the four leading large scale EOFs. The main discrepancy is the models' underestimation of the cyclone density in the Mediterranean, especially in its western part. The models' skill in reproducing the cyclone distribution is found correlated with their spatial resolution, especially in the vertical. The current improvement in model spatial resolution suggests that their ability to reproduce the Mediterranean cyclones would be improved as well.

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.

This work presents a statistical reconstruction of average mid-winter (DJF) temperature in Jerusalem since 1750. It is a first comprehensive attempt to reconstruct the temperature in Jerusalem, as a good representation of the Eastern Mediterranean (EM) climate. This representativeness is verified here. The data has been reconstructed by using a statistical model based on Principal Component Regression (PCR), using both instrumental data and high temporal resolution records of proxy data, including tree ring chronologies from Jordan, and records of DJF precipitation and Sea Level Pressure from central and Western Europe. A split validation procedure has resulted in a 0.73 correlation between observed and reconstructed temperature. The warming trend of last decades is well noted in the reconstruction and is in line with other studies. Winters which were cold/warm were historically documented as wet/dry, respectively, consistent with earlier studies pointing a strong relationship between Jerusalem temperatures and precipitation. It is shown here for the first time that the 'First Aliyah' (immigration) to Israel during 1882-1904 initiated during favouring climate conditions (cool and wet) to establish an agricultural community in the region. These conditions were found to be exceptional compared to other periods since 1750.

One of the costliest natural hazards around the globe is flash floods, resulting from localized intense convective precipitation over short periods of time. Since intense convective rainfall (especially over the continents) is well correlated with lightning activity in these storms, a European Union FP6 FLASH project was realized from 2006 to 2010, focusing on using lightning observations to better understand and predict convective storms that result in flash floods. As part of the project, 23 case studies of flash floods in the Mediterranean region were examined. For the analysis of these storms, lightning data were used together with rainfall estimates in order to understand the storms' development and electrification processes. In addition, these case studies were simulated using mesoscale meteorological models to better understand the local and synoptic conditions leading to such intense and damaging storms. As part of this project, tools for short-term predictions (nowcasts) of intense convection across the Mediterranean and Europe, and long-term forecasts (a few days) of the likelihood of intense convection, were developed and employed. The project also focused on educational outreach through a special Web site http://flashproject.org supplying real-time lightning observations, real-time experimental nowcasts, medium-range weather forecasts and educational materials. While flash floods and intense thunderstorms cannot be prevented, long-range regional lightning networks can supply valuable data, in real time, for warning the public, end-users and stakeholders of imminent intense rainfall and possible flash floods.