摘要 :
Precipitation in the eastern Mediterranean takes place during the cold season, when sea surface temperature is higher than the land surface temperature by 5℃-10℃. This temperature difference leads to the formation of the land br...
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Precipitation in the eastern Mediterranean takes place during the cold season, when sea surface temperature is higher than the land surface temperature by 5℃-10℃. This temperature difference leads to the formation of the land breeze-like circulation, which interacts with dominating westerlies and leads to an intense cloud formation over the sea ～10-20 km from the coastal line. As a result, most of the precipitation falls on the sea without reaching the land. At the same time the eastern Mediterranean region experiences a lack of freshwater. For investigating a possibility to shift the release of precipitation from sea to land, numerical simulations were performed using the Hebrew University 2-D cloud model and the 3-D Weather Research and Forecasting model, both operating with spectral bin microphysics, and the 3-D COSMO model of the German Weather Service applying a two-moment bulk parameterization for cloud physics. The respective results indicate that an increase in concentration of small aerosols leads to a delay in raindrop formation and fosters the formation of extra ice particles with low settling velocity. This ice is advected inland by the background wind. As a result, precipitation over land increases at the expense of precipitation over sea by 15%-20%. The spatial shift of precipitation from sea to land can be as large as 50-70 km depending on the wind speed of the background flow. These results suggest a new possibility to enhance precipitation in a particular region by cloud seeding with small aerosols.
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摘要 :
Precipitation in the eastern Mediterranean takes place during the cold season, when sea surface temperature is higher than the land surface temperature by 5℃-10℃. This temperature difference leads to the formation of the land br...
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Precipitation in the eastern Mediterranean takes place during the cold season, when sea surface temperature is higher than the land surface temperature by 5℃-10℃. This temperature difference leads to the formation of the land breeze-like circulation, which interacts with dominating westerlies and leads to an intense cloud formation over the sea ～10-20 km from the coastal line. As a result, most of the precipitation falls on the sea without reaching the land. At the same time the eastern Mediterranean region experiences a lack of freshwater. For investigating a possibility to shift the release of precipitation from sea to land, numerical simulations were performed using the Hebrew University 2-D cloud model and the 3-D Weather Research and Forecasting model, both operating with spectral bin microphysics, and the 3-D COSMO model of the German Weather Service applying a two-moment bulk parameterization for cloud physics. The respective results indicate that an increase in concentration of small aerosols leads to a delay in raindrop formation and fosters the formation of extra ice particles with low settling velocity. This ice is advected inland by the background wind. As a result, precipitation over land increases at the expense of precipitation over sea by 15%-20%. The spatial shift of precipitation from sea to land can be as large as 50-70 km depending on the wind speed of the background flow. These results suggest a new possibility to enhance precipitation in a particular region by cloud seeding with small aerosols.
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This study introduces a new conceptual model to explain the recently observed changes in winter precipitation over Israel. The model is based on our earlier published work (where a connection was reported between the occurrence of...
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This study introduces a new conceptual model to explain the recently observed changes in winter precipitation over Israel. The model is based on our earlier published work (where a connection was reported between the occurrence of major rain days (MRDs) in different parts of the country and three prototypes, A, B and C, of the 500 hPa trough axis orientation prevailing on MRDs) and on additional results obtained by an extension of that work in the present paper. The first part of the present study is devoted to the extension of our early work. Composite techniques have been used on National Center for Atmospheric Research 9NCAR)-National Meteoreological Center grid-point data for the rain seasons 1981-82 to 1985-86 to identify the sea-level pressure (SLP) distribution associated with each of the three 500 hPa prototypes. Prototype A (trough axis oriented from northwest to southeast, earlier shown to be associated with MRDs in northern Israel) was found in the present work to be associated with a surface low in the vicinity of Antalya, southern Turkey. Prototype B (trough axis oriented from north to south, earlier shown to be associated with MRDs in central Israel) was found in the present work to be associated with a surface low over southeastern turkey. Prototype C (trough axis oriented from northeast to southwest, earlier shown to be associated with MRDs in southern Israel) was found to be associated with elevated surface pressure over northwestern Turkey and a trough over eastern Turkey. In the second part of the study we used our results to construct a conceptual model of the mechanism responsible for the relative increases in seasonal (winter) rainfall over the southern part of the country and the decrease over the north. Using National Centers for Environmental Prediction-NCAR reanalysis data for the period 1982-2000, we demonstrated that the direct atmospheric agent responsible for this change in the spatial rainfall distribution is an increased frequency of occurrence of 500 hPa troughs oriented from northeast to southwest (Prototype C) accompanied by prominent positive SLP anomalies centred over turkey. Our analysis further shows that these atmospheric systems are consistent with the persistence of a positive phase of the North Atlantic Oscillation on the one hand and with latest IPCC predictions of precipitation patterns over the eastern Mediterranean basin on the other hand.
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We identify long transform faults that frame the eastern Mediterranean Sea and that were active during Jurassic and probably the Early Cretaceous, during the opening of the central Atlantic Ocean. We show that the African margin o...
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We identify long transform faults that frame the eastern Mediterranean Sea and that were active during Jurassic and probably the Early Cretaceous, during the opening of the central Atlantic Ocean. We show that the African margin of the eastern Mediterranean Sea is an 1800 km long transform fault that absorbed the Africa/Eurasia Jurassic left-lateral motion during the opening of the central Atlantic. We call this transform fault the Eastern Mediterranean South Transform fault (EMST). We identify two other transform faults that were active simultaneously and framed the eastern Mediterranean Sea during its formation. These are the Apulia Transform fault (AT) and the Eastern Mediterranean North Transform fault (EMNT). The AT, three hundred km north of the EMST, followed the southern boundary of the Apulia block. Still 300 km farther north, the EMNT formed the northern boundary of this eastern Mediterranean shear zone. This last fault has been destroyed over a large portion by the Hellenic subduction. We relate these transform faults to the kinematics of the Jurassic Africa/Eurasia motion. We conclude that the eastern Mediterranean Sea is a long pull-apart created by left-lateral shearing of the Adria block as it was structurally linked to Africa.
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Beverly Coodman-Tchernov The Mediterranean is the largest and deepest marginal sea on Earth. It is connected through the Straits of Gibraltar to the Atlantic Ocean in the west and via the Dardanelles to the Black Sea in the east. ...
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Beverly Coodman-Tchernov The Mediterranean is the largest and deepest marginal sea on Earth. It is connected through the Straits of Gibraltar to the Atlantic Ocean in the west and via the Dardanelles to the Black Sea in the east. The basin itself is divided into western and eastern basins by a relatively shallow ridge (~500 m) at the Straits of Sicily. The subject of this review is the larger eastern basin, which includes the Adriatic, Ionian,Aegean and Levantine Seas. The basin was formed as the last stage of the closing of the Tethys Ocean. It has a series of small plates with tectonically active boundaries, which were formed by the collision of Africa with Eurasia (Figure 1). It has diverse complex bathymetric features, both deep and shallow, and is semi-enclosed. Due to its unique features it represents a natural laboratory for a variety of globally important geohazard processes. (It is also the setting for unusual nutrient cycling in the water column,as discussed in the following article. Ed)
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We list sixty five fish species collected at depths greater than 500 m in the Levant Basin, including 10 depth records. The Levantine bathyal ichthyofauna is characterized by its eurybathy, with an upper bathymetric boundary that ...
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We list sixty five fish species collected at depths greater than 500 m in the Levant Basin, including 10 depth records. The Levantine bathyal ichthyofauna is characterized by its eurybathy, with an upper bathymetric boundary that permitted penetration of the shallow Gibraltar and Siculo-Tunisian sills, and a much lower bathymetric boundary than recorded for conspecifics elsewhere. The opportunistic and resilient ichthyofauna re-colonized recently the deep-sea following the last anoxic event (similar to 6 kyr), forming assemblages notably distinct from those in the western Mediterranean. The exploration and production of deep seabed hydrocarbons have raised the specter of severe direct impacts to the deep habitats. There is an urgent need for documenting the full extent of deep-sea biodiversity, and for providing information for the development of competent and pragmatic management plans and effective conservation policies.
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Beirut, the capital of Lebanon, which is located on the eastern shore of the Mediterranean basin, experiences high air pollution episodes. Annual average concentrations of coarse and fine particulate matter (PM2.5) as well as nitr...
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Beirut, the capital of Lebanon, which is located on the eastern shore of the Mediterranean basin, experiences high air pollution episodes. Annual average concentrations of coarse and fine particulate matter (PM2.5) as well as nitrogen oxides (NO_x) often exceed the World Health Organization (WHO) guidelines. Therefore, improving air quality in this region is essential. The Polyphemus/Polair3D modeling system is used here to investigate air pollution episodes in Beirut during 2 to 18 July 2011. The modeling domain covers two nested grids of 1 and 5 km horizontal resolution over greater Beirut and Lebanon, respectively. The anthropogenic emission inventory was developed earlier (Waked et al., 2012). TheWeather and Research Forecasting (WRF) model is used to generate the meteorological fields and the Model of Emissions of Gases and Aerosols from Nature (MEGAN) is used for biogenic emissions. The results of the study are compared to measurements from a field campaign conducted in the suburb of Beirut during 2-18 July 2011. The model reproduces satisfactorily the concentrations of most gaseous pollutants, the total mass of PM2.5 as well as PM2.5 elemental carbon (EC), organic carbon (OC), and sulfate. Ozone concentrations are overestimated and it appears that this overestimation results mainly from the boundary conditions.
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Atmospheric water vapor budget analysis is carried out in a rectangular domain of 3.04 x 10(5) km(2), over the eastern Mediterranean (EM) using NASA GOES-1 reanalysis gridded (2.5(0) longitude by 2(0) latitude) data set, for a per...
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Atmospheric water vapor budget analysis is carried out in a rectangular domain of 3.04 x 10(5) km(2), over the eastern Mediterranean (EM) using NASA GOES-1 reanalysis gridded (2.5(0) longitude by 2(0) latitude) data set, for a period of eight rainy seasons (October April) in 1985-1993. All days have been divided into 6 groups, based on rainfall amount, and the relationships between daily water vapor budget components have been studied in relation to precipitation amounts. We found that the mean rainy season precipitation. P over the study region is, about 260 mm. The highest precipitation category (over 2.2 mm/day) contributed 63% of the total rainfall, and the next category (0.9 to 2.2 mm/day) contributed another 22%. These two rainfall categories were accompanied by deep upper troughs extending from the Black Sea to Crete and a mean sea level (MSL) cyclone near Cyprus. For the rest of the rainfall categories the upper air flow was nearly zonal, with no clear MSL cyclonic activity. The western boundary exhibited a net moisture inflow, increasing with rainfall amount. The southern boundary moisture inflow becomes significant only for the highest rainfall category. The correlation between P and both inflow and outflow was (+0.45), in agreement with similar studies over the US Midwest in summer. However, in contrast to the latter studies - our study shows no correlation between P and moisture flux divergence (MFD). A possible explanation for this is that winter rainfall over the Eastern Mediterranean is mostly associated with cold fronts, whereas in the Midwest convective rain develops in the warm sector, near the maximum MFD. Finally, both, recycling ratio R. and the correlation between daily P and E support the idea that rainfall over the EM originates, at least partly, in humidity evaporating from the Sea within the region. Copyright (C) 2009 Royal Meteorological Society
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The Eastern Mediterranean Sea is a remnant of a deep Mesozoic oceanic basin, now almost totally consumed as a result of long-term plate convergence between Eurasia and Africa. The present-day surface morphology of the Eastern Medi...
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The Eastern Mediterranean Sea is a remnant of a deep Mesozoic oceanic basin, now almost totally consumed as a result of long-term plate convergence between Eurasia and Africa. The present-day surface morphology of the Eastern Mediterranean relates both to the early history of formation of the deep basins and the recent geodynamic interactions between interfering microplates. Among the most conspicuous morphologic features of the basin is an arc-shape, elongated and wide, bathymetric swell bisecting the entire basin from the Ionian to Levantine areas, known as the Mediterranean Ridge. During the last decade this tectono-sedimentary accretionary prism, which results from the Hellenic subduction, has been intensively surveyed by swath mapping, multichannel seismic profiling and deep dives. We present here, and briefly discuss, the main morphological characteristics of this feature as derived from swath bathymetric data that considerably help to better assess the lateral and north–south morphostructural variability of the Mediterranean Ridge. This study reveals that the characteristics and morphostructural variability of the Mediterranean Ridge are related to: (1) a specific incipient collision geodynamic setting south of Crete, where the African and Aegean continental margins are nearly in contact, (2) a unique regional kinematics, controlled by frontal convergence south of Crete (central Mediterranean Ridge) and oblique subduction with opposite sense of shear for the western (Ionian) and eastern (Levantine) domains of the Mediterranean Ridge, that explain the lateral variations of deformation and (3) particularities of its sedimentary cover, which includes massive salt layers within the outer Mediterranean Ridge and local salt deposits within the inner domains, that control the north–south morphostructural variability of the sedimentary wedge.
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Based on recent collections made in Cyprus, six species of Pottiaceae (Didymodon eckeliae, D. sicculus, Pottiopsis caespitosa, Tortula acaulon, T. revolvens and T. wilsonii) are newly reported for this country.
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