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1.
All the available historic records of sea level and appropriate weather charts have been used to study storm surges in the northern part of the Sea of Japan. The generation of surges in this area was investigated by means of a two-dimensional numerical model. Computed sea levels were compared with hourly observed residual sea levels in De-Kastri. The agreement between computed and observed storm surges is quite satisfactory. The relative importance of various meteorological parameters and bottom topography in formation of the strong storm surge on 20–21 September 1975 was studied numerically.  相似文献   

2.
Almost every year in the winter months (December–February), the vast Indo-Gangetic Plain south of the Himalaya is affected by dense fog. This fog is considered as radiational fog, and sometime it becomes smog (when it mixes with smoke). The typical meteorological, topographic and increasing pollution conditions over the Indo-Gangetic Plain are perhaps the common contributing factors for fog formation. In the present study, the North Indian fog has been successfully mapped and analysed using NOAA-AVHRR satellite data. In the winter seasons of 2005–06, 2006–07 and 2007–08, the fog-affected area has been found to cover about 575,800 km2, 594,100 km2 and 478,000 km2, respectively. Less fog in 2007–08 may be the consequence of high fluctuations in the meteorological parameters like temperature, relative humidity and wind speed as related to the prevailing synoptic regime for that season. The dissipation and migration pattern of fog in the study area has also been interpreted on the basis of the analysis of both meteorological and satellite data. Further analysis of the fog-affected area allowed identifying more fog-prone regions. Analysis of past fog-affected days and corresponding meteorological conditions enabled us to identify favourable conditions for fog formation viz. air temperature 3–13°C, relative humidity >87%, wind speed <2 m/s and elevation <300 m. Based on the observations of past fog formation and corresponding governing parameters, fog for few selected days could be predicted in hind-sight and later verified with NOAA images.  相似文献   

3.
Interhemispheric anti-phasing of rainfall during the last glacial period   总被引：1，自引：0，他引：1  
We have obtained a high-resolution oxygen isotopic record of cave calcite from Caverna Botuverá (27°13′S, 49°09′W), southern Brazil, which covers most of the last 36 thousand years (ka), with an average resolution of a few to several decades. The chronology was determined with 46 U/Th ages from two stalagmites. Tests for equilibrium conditions show that oxygen isotopic variations are primarily caused by climate change. We interpret our record in terms of meteoric precipitation changes, hence the variability of South American Monsoon (SAM) intensity. The oxygen isotopic profile broadly follows local insolation changes and shows clear millennial-scale variations during the last glacial period with amplitudes as large as 3‰ but with smaller centennial-scale shifts (<1‰) during the Holocene. The overall record is strikingly similar to, but strongly anti-correlated with, a number of records from the Northern Hemisphere.We compared our record to other precisely dated contemporaneous records from Hulu Cave eastern China. Minima in δ18O (wet periods, intense SAM) at our site are synchronous with maxima in δ18O (dry periods, weak East Asian Monsoon, EAM) in eastern China (within precise dating errors) and vice versa. This anti-phased precipitation relationship between two low-latitude locations may be interhemispheric in extent, based on comparison with records from other sites. Precipitation anti-phasing may be related to north–south shifts in the mean position of the intertropical convergence zone (ITCZ) and asymmetry in Hadley circulation in two hemispheres, associated not with seasonal changes as observed today, but with millennial-scale climate shifts. The millennial-scale atmospheric see-saw patterns that we observe could have important controls and feedbacks on climate within hemispheres because of water vapor's greenhouse properties.  相似文献   

4.
Počakal  Damir 《Natural Hazards》2003,29(3):543-552
This paper presents hail characteristics for two separate periods (1981–1990,1991–1999) in the western part of the hail protected area along the Croatianand Slovenian border. The first period is characterised by full application ofhail suppression technology. The protected area was covered with a sufficientnumber of hail suppression rockets, rockets launching was permitted across theSlovenian border aimed at early seeding, and Slovenia in that time had also theoperative hail suppression system. The second period is characterised withsignificantly lower application of hail suppression technology compared withfirst period. During the independence war in Croatia, because of a lack ofrockets and other objective circumstances, appropriate rocket hail suppressionwas missing. This work examines whether hail characteristics on the border areahave changed, taking into account the changes in suppression. Results show thatthe average diameter of hailstones and duration of hailfall slightly increasedin second period. Also, there is an increase in the number of areas with alarger ratio of hail producing heavy damage, compared with first period. On thebasis of data from five meteorological stations, it is visible that, as a resultof implementation of the hail suppression system, the average number of dayswith solid precipitation on that area in period April–October has reduced,compared with the period when there was no hail suppression system.  相似文献   

5.
A continuously operated gas monitoring station was emplaced within the epicentral area of the NW Bohemian swarm earthquakes overlying directly the active Mariánské Lázně fault. The recordings of 8-month continuous monitoring period are presented. The variations in radon concentrations are similarly to variations in CO2, i.e. CO2 is considered to be the carrier gas for radon. Very small diurnal variations in gas concentration are caused by the earth tides, as daily variations in meteorological conditions cannot explain a short daily minimum at midday times. Sudden changes in gas concentration, which clearly exceed these diurnal variations occur and are always linked with seismic activities. Decreased gas concentration may indicate compression resulting in reduced fault permeability as is implied by negative peaks following local earthquake swarms. A sudden increase in CO2 and Rn concentration may indicate an increased fault permeability caused by stress redistribution, giving rise to opening of migration pathways. This implies a repeatedly sudden rise in gas concentration before local earthquake swarms. Several variations in gas concentration were monitored linked with remote earthquakes of ground motion amplitudes  >1 μm. These seismic events are accompanied by an interference of the diurnal gas concentration–stress-cycle along the Mariánské Lázně fault. However, if shocks of remote earthquake can alter properties of the migrating fluids or the fault properties it can be suggested that these are able to trigger local seismicity, as indicated in the case of the Slovenia earthquake on 12th July 2004.  相似文献   

6.
This paper discusses the characteristics of high-impact weather events based on available data during 1960–2009, including the frequency and extreme value of rainstorm, typhoon, thunderstorm, strong wind, tornado, fog, haze and hot days in Shanghai, China. The frequency and spatial distribution of meteorological disasters and their impacts on both human and property during 1984–2009 are also discussed. Examination of the frequency indicates a decreasing trend in the occurrence of typhoon, thunderstorm, strong wind, tornado and fog, and an increasing trend in the occurrence of rainstorm, haze and hot days. The number of casualties caused by meteorological disasters appears to show a slight decreasing trend while the value of direct economic loss is increasing slightly during 1984–2009, and the number of collapsed or damaged buildings and the area of affected crops have no significant trend in Shanghai. These results can be attributed to the great efforts for prevention and mitigation of meteorological disasters made by Shanghai government in recent 60 years. With global climate change, urbanization and rapid economic development, Shanghai has become more vulnerable to high-impact weather and meteorological disaster, especially precipitation extreme, summer high temperature, haze and typhoon, so more strategies of mitigation and/or adaptation of natural disasters are quite useful and necessary for local government and the public in the future.  相似文献   

7.
The Late Quaternary Amazon deep-sea fan provides a modern analogue to ancient fan systems containing coarse-grained hydrocarbon reservoirs. Sand lenses deposited within the Amazon Fan, due to abrupt shifts in channel pathways called avulsion events, were drilled as part of ODP Leg 155. The hemipelagic sediment directly on top of the avulsion sands was dated using primarily AMS radio carbon dating. This dating shows that these large sand lobes (1 km3) are triggered by relatively small, millennial scale changes in marine transgression and regression (±5–10 m). Relative sea level also controls the architecture of the Channel–levee distributive systems within the Amazon Fan. For example prior to 22 k calendar years BP there is a tripartite channel system. After 22 ka there is only one active Channel–levee system. Transitions between the multi-channel and single channel configurations are related to variations in the volume of sediment supply resulting in aggradation or erosion of channel floor and levee growth in the canyon-channel transition area. The sensitivity of the Amazon deep-sea Fan sedimentation to relatively small changes in sea level supports one of the central assumptions of the theory of Sequence Stratigraphy. In addition this study demonstrates how traps for hydrocarbons may have been formed in ancient fan systems.  相似文献   

8.
The infrared spectroscopic measurements of synthetic and natural carbonate samples show that significant frequency shifts in the v2 and v4 vibrational bands of the carbonate ion group occur in the calcite-rhodochrosite and calcite-magnesite mineral series as a function of the chemical composition. These shifts are due to cationic substitution, reflecting the different ionic raddii and masses of the end-members. A tentative model for the variations of v2 and v4 in the ternary system CaCO3–MnCO3–MgCO3 is presented.  相似文献   

9.
M. Y. Une 《GeoJournal》1982,6(2):129-140
Frost damage on coffee plantations in south-central Brazil is not a frequent occurrence. However, when this area is affected by a severe frost — as happened in August of 1975 — the consequences for the agricultural economy of south-central Brazil and the socio-economic condition of the rural labourers are serious.In this paper the meteorological characteristics of a frost condition are outlined and their physiological effects upon coffee bushes are stated. A differentiation is made as to the timely occurrence of frosts and their effects on crops. If the frost hits during harvest time (April through June) the beans may be burned and a qualitative loss may ensure. If the frost occurs after the harvest, only the coffee bushes are affected and they may have recovered by the following agricultural year. The most devastating frosts are those that occur late in winter (August-September) because they kill the buds and the flowers so that next year's harvest will be lost.Coffee in south-central Brazil is usually grown on plantations of 10 to 100 ha, and 100 to 1000 ha. There has been a trend to expand the coffee growing area into Mato Grosso-Rondonia, while in the state of Parana, where frosts are more severe but the soils are better, coffee growing in large estates has intensified. Moreover, the introduction of new methods of planting and mechanization of the agricultural work have brought about an intensification of coffee production. Analysis of the improvements in cultivating pratices and of agricultural mechanization that these two processes have caused a drastic reduction in the demand for agricultural labourers. Added to this, the possibilities of rural employment have also been adversely affected by the trend among many coffee growers to introduce other crops into their estates in order to minimize their losses due to frost.  相似文献   

10.
Beer  Tom 《Natural Hazards》2001,23(2-3):157-169
Meteorological hazards are usually considered to be tropical cyclones, droughts, hail-storms, severe storms and their effects such as tsunamis, storm surges, wildfire, and floods. Urban air pollution is not normally considered to be a meteorological hazard. This view has arisen because the causes of urban air pollution – industrial and motor vehicleemissions – are not meteorological in nature. Air pollution episodes, however, are sporadic in nature and their occurrence depends on a particular combination of meteorological factors. This is true even in megacities such as Mexico City, Manila, and Los Angeles that have acquired a reputation for polluted air. Analyses of air pollution episodes and hospital admissions from many countries indicate that thereis a significant increase in morbidity and mortality as a result of such episodes.Time-series studies undertaken in Sydney have shown that particulate matter, ozone and nitrogen dioxide are the pollutants that are primarily responsible for adverse health effects in that city.Air pollution, and in particular particulate matter, is believed to be responsible for just under 400 premature deaths per year in Sydney alone. This death rate is over twenty times larger than deaths due to other meteorological hazards. Part of the reason for the low death rate for the more traditional meteorological hazards is that the provision of high quality numerical weather prediction, coupled with modern communications technology, has enabled emergency service personnel to take appropriate action.Air quality forecasting systems can play an important role in mitigating the adverse effects of air pollution. The forecasts will affect the behaviour of susceptible individuals, and thus reduce adverse health effects. The outputs from forecasting systems can also be used to provide improved estimates of the total exposure to air pollutants of the inhabitants who areat risk. Such improved estimates can then be used in conjunction with longitudinal studies ofhealth effects to obtain better understanding of the complex interaction between air quality and health.  相似文献   

11.
Magnetic susceptibility (MS) of surface sediment varies systematically across the Loess Plateau in central China, decreasing exponentially from >200×10−8 m3/kg at the northern margin of the Qinling Shan to ≤30×10−8 m3/kg near the southern margin of the Mu Us Desert. MS correlates highly with loess median grain size (r2=0.79), which decreases south-southeastward across the plateau. It also correlates with mean annual temperature (MAT) and mean annual precipitation (MAP) (r2=0.58 and 0.60, respectively), and with their product MAT×MAP (r2=0.83), which is considered a measure of potential pedogenic activity. Because regional isopleths depicting grain size and the primary meteorological parameters are nearly parallel, it is difficult to determine their relative influence on MS. A simple MS model, based on the observed spatial variation in loess thickness, permits quantitative assessment of the effect of the dust accumulation rate on the MS signal of surface sediment and isolates the likely role of climate in the production of magnetic minerals. The model suggests that 84% of the loess MS variance is dictated by the diluting effect of dust and 10–11% is associated with meteorological factors, primarily precipitation. The observed and modeled relationships support hypotheses that attribute variations in MS in the loess-paleosol succession to varying rates of dust deposition and in situ production of magnetic minerals in the accretionary soils, both of which are controlled by monsoon climate.  相似文献   

12.
As political geography searches in desperation for new (theoretical) directions to follow, this paper argues that the category of the ‘political’ has already curved back on itself, attaining the status of the ‘transpolitical’. Hereinafter, politics will never finish replaying its own disappearance as effect. This curvature is itself associated with profound shifts in the experience of history and time, of geography and space, and of the very ideas of theory, politics and events—shifts which continue to fascinate, haunt and transfix political geography in the enigmatic hereafter of the transpolitical. Adopting the motifs of s(ed)uction, transpearing, superficial abysses, and hypertelia (the ‘end of the end’), the paper assesses: the transpolitical figures of anomaly, ecstasy, obesity and obscenity; the irruption of the hyperreal (the more real than the real); the mutation of the political scene of representation into the transpolitical ob-scene of pornogeography; the fatal strategies pursued by the masses in relation to the spectre of the (trans)political; and the challenge of a transfinite universe for conjuring theoretical practice at the end(s) of political geography. Beginning with the transition from the political era—dominated by the transgressive figure of anomie and the emancipatory promise of revolutionary subl(im)ation—to the transpolitical simulacrum—characterized by the errant figure of anomaly and the superficial abyss of potentialization—the paper attempts to animate a transpolitical geography which affirms the s(ed)uction of superficial abysses and instantiates an ethics of the transpearing event.  相似文献   

13.
The Alkaline porphyries in the Beiya area are located east of the Jinshajiang suture, as part of a Cenozoic alkali-rich porphyry belt in western Yunnan. The main rock types include quartz-albite porphyry, quartz-K-feldspar porphyry and biotite–K-feldspar porphyry. These porphyries are characterised by high alkalinity [(K2O + Na2O)% > 10%], high silica (SiO2% > 65%), high Sr (> 400 ppm) and 87Sr/86Sr (> 0.706)] ratio and were intruded at 65.5 Ma, between 25.5 to 32.5 Ma, and about 3.8 Ma, respectively. There are five main types of mineral deposits in the Beiya area: (1) porphyry Cu–Au deposits, (2) magmatic Fe–Au deposits, (3) sedimentary polymetallic deposits, (4) polymetallic skarn deposits, and (5) palaeoplacers associated with karsts. The porphyry Cu–Au and polymetallic skarn deposits are associated with quartz–albite porphyry bodies. The Fe–Au and polymetallic sedimentary deposits are part of an ore-forming system that produced considerable Au in the Beiya area, and are characterised by low concentrations of La, Ti, and Co, and high concentrations of Y, Yb, and Sc.The Cenozoic porphyries in western Yunnan display increased alkalinity away from the Triassic Jinshajiang suture. Distribution of both the porphyries and sedimentary deposits in the Beiya area are interpreted to be related to partial melting in a disjointed region between upper mantle lithosphere of the Yangtze Plate and Gondwana continent, and lie within a shear zone between buried Palaeo-Tethyan oceanic lithosphere and upper mantle lithosphere, caused by the subduction and collision of India and Asia.  相似文献   

14.
Speleothem carbon and oxygen isotopic records from Onondaga Cave, south-central Missouri, and Beckham Creek Cave, north-central Arkansas, are compared with the Cupola Pond and Oldfield Swamp pollen series from southeastern Missouri and the Rodgers Shelter and Modoc Shelter vertebrate biostratigraphic sequences from central Missouri and southwestern Illinois. Similar, and roughly contemporaneous, shifts between deciduous forest and steppe indicators throughout the Holocene are revealed in each database. These independent proxies record steppe conditions between approximately 9000 and 1500 cal yr B.P. A shift toward lighter speleothem carbon may reflect a change from warm and dry to cool and dry conditions between 4500 and 3000 yr B.P. The sensitive response of speleothem δ13C to changes in vegetation emphasizes their importance as paleoclimate records in an area containing few other millenial-scale climate proxies.  相似文献   

15.
We compare six high-resolution Holocene, sediment cores along a S–N transect on the Norwegian–Svalbard continental margin from ca 60°N to 77.4°N, northern North Atlantic. Planktonic foraminifera in the cores were investigated to show the changes in upper surface and subsurface water mass distribution and properties, including summer sea-surface temperatures (SST). The cores are located below the axis of the Norwegian Current and the West Spitsbergen Current, which today transport warm Atlantic Water to the Arctic. Sediment accumulation rates are generally high at all the core sites, allowing for a temporal resolution of 10–102 years. SST is reconstructed using different types of transfer functions, resulting in very similar SST trends, with deviations of no more than ±1.0/1.5 °C. A transfer function based on the maximum likelihood statistical approach is found to be most relevant. The reconstruction documents an abrupt change in planktonic foraminiferal faunal composition and an associated warming at the Younger Dryas–Preboreal transition. The earliest part of the Holocene was characterized by large temperature variability, including the Preboreal Oscillations and the 8.2 k event. In general, the early Holocene was characterized by SSTs similar to those of today in the south and warmer than today in the north, and a smaller S–N temperature gradient (0.23 °C/°N) compared to the present temperature gradient (0.46 °C/°N). The southern proxy records (60–69°N) were more strongly influenced by slightly cooler subsurface water probably due to the seasonality of the orbital forcing and increased stratification due to freshening. The northern records (72–77.4°N) display a millennial-scale change associated with reduced insolation and a gradual weakening of the North Atlantic thermohaline circulation (THC). The observed northwards amplification of the early Holocene warming is comparable to the pattern of recent global warming and future climate modelling, which predicts greater warming at higher latitudes. The overall trend during mid and late Holocene was a cooling in the north, stable or weak warming in the south, and a maximum S–N SST gradient of ca 0.7 °C/°N at 5000 cal. years BP. Superimposed on this trend were several abrupt temperature shifts. Four of these shifts, dated to 9000–8000, 5500–3000 and 1000 and 400 cal. years BP, appear to be global, as they correlate with periods of global climate change. In general, there is a good correlation between the northern North Atlantic temperature records and climate records from Norway and Svalbard.  相似文献   

16.
A system for effectively forecasting flash floods of the Arno River (Tuscany, Italy) should provide a flood warning with 10–12 h of lead time, primarily in order to evacuate the city of Florence. This goal may be achieved by acquiring and processing meteorological and hydrological data in real-time and, accordingly, by releasing alarms at different levels of reliability and concern. Through the application of both procedural language and expert system techniques, a prototype was developed which can readily handle a variety of relevant information and make predictions on flood hazard in Florence. The system was fairly successfully tested by processing simple meteorological data which enable a 24 hour forewarning to be released.  相似文献   

17.
This study presents a structural analysis based on hundreds of striated small faults (fault-slip data) in the Amman area east of the Dead Sea Transform System. Stress inversion of the fault-slip data was performed using an improved Right-Dihedral method, followed by rotational optimization (TENSOR Program, Delvaux, 1993). Fault-slip data (totaling 212) include fault planes, striations and sense of movements, are obtained from the Turonian Wadi As Sir Formation, distributed mainly along the southern side of the Amman – Hallabat structure in Jordan the study area. Results show that σ1 (SHmax) and σ3 (SHmin) are generally sub-horizontal and σ2 is sub-vertical in 8 of 11 paleostress tensors, which are belonging to a major strike-slip system with σ1 swinging around N to NW direction. The other three stress tensors show σ2 (SHmax), σ1 vertical and σ3 is NE oriented. This situation explained as permutation of stress axes σ1 and σ2 that occur during tectonic events and partitioned strike slip deformation. NW compressional stresses affected the area and produced the major Amman – Hallabat strike-slip fault and its related structures, e.g., NW trending normal faults and NE trending folds in the study area.The new paleostress results related with the active major stress field of the region the Dead Sea Stress Field (DSS) during the Miocene to Recent.  相似文献   

18.
The major weather hazards in Calabar, a coastal town in Nigeria during both winter and summer hemispheres are discussed using meteorological data for 32 years (1951–1982). Results show that during the winter months of November to March, which are usually referred to as the dry season in Nigeria, frequency of occurrence of fog and harmattan dust haze is low. Summer patterns of precipitation are typical of the equatorial zone.Since 1980, poor visibility associated with fog and harmattan haze have become serious while high rates of erosion and flooding due to heavy rain are aggravated by human activities.  相似文献   

19.
Analysis of hydraulic heads and chemical compositions of Devonian formation waters in the west central part of the Alberta Basin, Canada, characterizes the origin of formation waters and migration of brines. The Devonian succession in the study area lies 2000–5000 m below the ground surface, and has an approximate total thickness of 1000 m and an average slope of 15 m/km. Four Devonian aquifers are present in the study area, which form two aquifer systems [i.e., a Middle–Upper Devonian aquifer system (MUDAS) consisting of the Elk Point and Woodbend–Beaverhill Lake aquifers, and an Upper Devonian aquifer system (UDAS) consisting of the Winterburn and Wabamun aquifers]. The Ireton is an effective aquitard between these two systems in the eastern parts of the study area. The entire Devonian succession is confined below by efficient aquitards of the underlying Cambrian shales and/or the Precambrian basement, and above by overlying Carboniferous shales of the Exshaw and Lower Banff Formations.The formation water chemistry shows that the Devonian succession contains two distinct brine types: a ‘heavy brine,’ located updip, defined approximately by TDS >200 g/l, and a ‘light brine’ with TDS <200 g/l. Hydraulic head distributions suggest that, presently, the ‘light brine’ attempts to flow updip, thereby pushing the ‘heavy brine’ ahead. The interface between the two brines is lobate and forms large-scale tongues that are due to channeled flow along high-permeability pathways. Geological and hydrogeochemical data suggest that the following processes determined the present composition of the ‘light’ and ‘heavy’ brines: original seawater, evaporation beyond gypsum but below halite saturation, dolomitization, clay dehydration, gypsum dewatering, thermochemical sulfate reduction (TSR), and halite dissolution. The influx of meteoric (from the south) and metamorphic (from the west) waters can be recognized only in the ‘light brine.’ Albitization can be unequivocally identified only in the ‘heavy brine.’ The ‘heavy brine’ may be residual Middle Devonian evaporitic brine from the Williston Basin or the Elk Point Basin, or it may have originated from partial dissolution of thick, laterally extensive Middle Devonian evaporite deposits to the east of the study area. The ‘light brine’ most probably originated from dilution of ‘heavy brine’ in post-Laramide times.  相似文献   

20.
The Kuroshima Knoll is about 26 km south of Ishigaki Island in the southern part of the Ryukyu Arc. The area is considered to be the source area of “The 1771 Yaeyama Earthquake Tsunami”, which was due to the submarine landslide caused by an earthquake. It has been cleared from some investigations using “Dolphin 3K” and “Shinkai 2000” that there are large-scale dead Calyptogena colonies, many gravels of fallen dolomite chimneys and carbonates on the top of the Knoll [Matsumoto, T., Uechi, C., Kimura, M., 1997; Machiyama, H., Matsumoto, T., Matsumoto, R., Hattori, M., Okano, M., Iwase, R., Tomaru, H., 2001b.]. Carbonates of Kuroshima Knoll have various shapes and macroscopic textures. These have been classified into 4 types; shell crust (pavement), chimney, burrow, and nodule. It is clear that all chimney and burrow carbonates are composed of dolomite, while shell curst and nodule are composed of calcite, sometimes both calcite and dolomite. These carbonates are considered to have been formed by cold seep, because they are characterized by the light carbon isotopic ratio (semi-biogenic) and the heavy oxygen isotopic ratio. This suggests that methane hydrate layers develop under this survey area and the water that has the heavy oxygen and the light carbon isotopic ratio is derived from the dissociation of methane hydrate.  相似文献   

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