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1.
The ‘Northern British Cooking-Pot’ stems from Saxo-Norman antecedents, and is found in two basic light-coloured fabrics, the ‘Gritty Northern’ and the ‘Staxton Ware Type’. From Yorkshire the type spread in the early thirteenth century west over the Pennines to Carlisle and thence to south-west Scotland. Present evidence suggests that while ‘Gritty Northern’ ware traditions may have spread to eastern Scotland by an overland route, there is reason to suppose there was close contact between the potteries of Fife and Angus and those of the Scarborough district in the late thirteenth century. While in Scotland there is a considerable hybridization of forms and fabrics, ‘Gritty Northern’ ware appears predominant north of the Forth, ‘Staxton Type’ ware to the south. In the fourteenth century distinctively Scottish local variants occur. French and Low Countries influences on early Scottish pottery are discussed, a tentative Scottish cooking-pot type-series put forward, and a gazetteer of sites producing rim-sherds given.  相似文献   

2.
本文尝试使用高分辨率的清代日记资料,复原1868年长江中下游各地夏季降水情况,辨析出当年梅雨季节各地的降水时间和主要降水过程,发现该年发生了"二度梅"现象。该年入梅较早,6月8日全流域降水就已经开始,且14日以后雨带有北抬趋势,但很快南撤出长江流域,引起降水中断。直至7月5日开始,雨带又重新占据长江南岸,带来第二段梅雨。"二度梅"的发生可能与副高持续南撤有关。  相似文献   

3.
The Lacy-Shellard index of driving rain is found too rough because it ignores wind direction and relies on annual means of precipitation and wind speed. A more refined driving-rain index is proposed as the product of total precipitation and the frequency of wind speeds of more than 5 meters per second. A study based on stations in the European USSR suggests that 30 to 40 percent of total precipitation strikes walls and other vertical surfaces north of Lat. 55°N, but that the percentage rises to about 70 percent along the coasts of the Barents Sea, the Baltic Sea and the Gulf of Finland. A technique is proposed for measuring the amount of precipitation striking walls of varying exposure. The amount is obtained by multiplying the total precipitation by the frequency of wind directions on rainy days.  相似文献   

4.
敦煌莫高窟文物具有唯一性和脆弱性,干燥环境是壁画和塑像长久保存的保障,降雨是病害发生诱因。为了弄清降雨对文物的损害机制,本研究通过气象监测数据分析和野外人工降雨模拟试验,分析莫高窟降雨分布特征和窟顶戈壁降雨入渗和产流规律,为开展洞窟内壁画病害发育机理分析和实施莫高窟洪水风险预控提供理论依据。25年气象监测数据分析表明,莫高窟区域多年平均降水量39mm,集中在5~8月,降雨类型主要为微雨和小雨,频现大于76%,大雨及暴雨均为突发性强降雨,频现仅为1.5%,常常伴随区域洪水的发生。降雨模拟试验结果表明,当平均降雨强度0.75mm/min,降雨历时160min时,入渗湿润锋迁移至深度80cm左右即趋于平衡。但是,高密度电阻率探测表明洞窟地层2~3m处,水分饱和度可达60%左右,极易带动可溶盐向壁画地仗层富集,致使病害发生发展。经计算,窟顶戈壁径流系数0.016,产流能力非常低。区域洪水主要来源于莫高窟周边戈壁及野马山地带降雨汇流。  相似文献   

5.
Palaeomagnetic and geochemical studies of Cambrian–Ordovician serpentinite in the Highland Border Complex (HBC), a tectonic terrane along the Highland Boundary Fault (HBF) in Scotland, indicate that the HBF was a conduit for fluids in the Carboniferous–Permian. The fluids caused dolomitization, silicification, and haematite authigenesis. Both red dolomitized serpentinite and relatively unaltered serpentinite were sampled at multiple localities. The unaltered serpentinite contains a poorly defined magnetization with westerly declinations that resides in magnetite and has a pole which plots well off the apparent polar wander path. Most specimens of the red dolomitized serpentinite contain a magnetization with southerly declinations and negative inclinations that resides in haematite. A regional fold test suggests that this magnetization post‐dates tilting and the pole positions for the different locations fall on the Carboniferous to Permian part of the apparent polar wander path. In some specimens of red dolomitized serpentinite, alternating field (AF) demagnetization prior to thermal treatment removes a component with a similar direction. Dolomitized basement rocks along the fault contain a similar although apparently slightly older magnetization. Fluid inclusion and geochemical studies indicate that the fluids were hydrothermal in origin (110–240°C) and had a range of sources. The Carboniferous–Permian magnetization in haematite is interpreted as a chemical remanent magnetization that formed when warm fluids moved along the fault zone and caused haematite authigenesis. The component removed by AF treatment is interpreted as a thermal resetting of primary magnetite by the fluids. The variability of the palaeomagnetic, fluid inclusion, and stable isotope results suggests that there were probably multiple flow events that caused the alteration. The origin of the fluids could be related to the intrusion of late Carboniferous dikes in central Scotland and/or to reactivation of the HBF in the Carboniferous–Permian.  相似文献   

6.
Abstract

The variability of the Normalized Difference Vegetation Index (NDVI) in north east India in response to rainfall and temperature was analysed using twice-monthly NOAA/AVHRR satellite imagery acquired during 1982–2002 from the GIMMS (Global Inventory Modeling and Mapping Studies) data-set. Corresponding rainfall and temperature estimates were extracted from the Climate Research Unit's CR TS 2.1 data-set for 34 study sites, chosen using the GLC 2000 land use categories. The selected sites represent nine land use categories under differing institutional frameworks. Results showed a weak linear relationship between the growing season rainfall and NDVI range when plotted in a scatter diagram. The negative correlation between NDVI and rainfall and temperature and NDVI in the study area was accentuated during the growing season and a one- and two-month lag for rainfall and temperature respectively was operating. A gain coefficient image to determine the temporal change in NDVI during the 21-year period indicated a consistent decline for much of the study area. Among the study sites those under state protection fared better than sites under other institutional frameworks. Along with rainfall and temperature, land use and institutional frameworks emerged as causative factors in the dynamics of vegetation greenness in north east India.  相似文献   

7.
This paper examines the feasibility of deriving a climatology of the diurnal variations of the wind in the 85–120 km region from the tidal components of temperature, density, and composition contained in the new COSPAR International Reference Atmosphere, CIRA-1986, Part I: Thermosphere Models [(1988), Adv. Space Res.8, 9]. To derive the wind field, we used the zonal and meridional momentum equations which have been modified from the characteristic scales of the tidal components observed in the 85–120 km region. The CIRA temperature and density model was used to derive the eastward (westerly) and northward (southerly) pressure gradient forces which serve as the forcing functions in the coupled momentum equations. Ground-based wind data from the Mesosphere-Lower Thermosphere (MLT) radar network is used as an independent data set to check the accuracy of the derived tidal wind model. At midlatitudes, the model reproduces some of the general features observed in the radar tidal data, such as the dominant semidiurnal tide with increasing amplitude with height and clockwise (counterclockwise) rotation of the velocity vector observed in the northern (southern) hemisphere. The model overestimates the semidiurnal amplitudes observed by radar by 50–75% during most seasons with the best agreement found during the equinoctial months. The model exhibits little phase variation with height or season, whereas the radar data exhibit a downward phase progression during most seasons (other than summer) characteristic of upward propagating tidal waves, and large seasonal phase variations associated with seasonal changes in vertical wavelengths. The diurnal tidal amplitudes, which are generally 5–20 m s−1 at mid-latitude radar stations and are dominant over the semidiurnal amplitudes at lower latitudes, are less than 5 m s−1 at all latitudes in the model.  相似文献   

8.
Main features of spatial distribution and time variations of meteorological parameters in the Southern hemisphere at altitudes 25–80 km are reviewed on the basis of zonal empirical models revised in 1982. Meridional distribution and seasonal variations are analysed. For comparison purposes with the Northern hemisphere, a model developed by Cole and Kantor in 1978 is used. It is revealed that the compilation of new models of the Southern hemisphere atmosphere has not resulted in substantial revision of hemispheric-structure outlined earlier in studies conducted in the Central Aerological Observatory. Meridional distribution of the parameters in summer is characterized by higher values of temperature, pressure and density gradients in the stratosphere of the Southern hemisphere than in that of the Northern hemisphere. This resulted in greater advancement of the core of the summer-time easterly (low towards the equator in the Southern hemisphere than in its northern counterpart. In winter, meridional temperature gradients in the middle stratosphere are greater in the Southern hemisphere than those in the Northern hemisphere, however, rapid attenuation of the gradients with height is observed in the Southern hemisphere, and above 35–40 km they become negative near 50–60°S, in contrast to positive values typical for the Northern hemisphere stratosphere. In the wind field, specific features of the Southern hemisphere westerly flow are high intensity and relatively low altitude of the maximum speed (as compared to the Northern hemisphere).The phases of the annual temperature wave at low latitudes are similar south and north of the equator; south of 30°S a reversal of the phase is observed. The semi-annual oscillation of temperature and wind is less pronounced in middle and high latitudes of the Southern hemisphere than in the Northern hemisphere.The origin of the primary differences between the hemispheres is related mainly to lower intensity of large-scale stratospheric processes in the Southern hemisphere as compared to those in the Northern hemisphere, which is confirmed by values of the standard deviation of the parameters in the two hemispheres.In summer, temperature and pressure fields based on satellite data are symmetric relative to the poles in both hemispheres. In winter, the distortion of the mean pressure field in the mesosphere may be as great in the Southern as in the Northern hemisphere.  相似文献   

9.
The new Siberia     
This paper assesses relationships between Scottish ice climbing and daily weather conditions between 1961 and 1990. Synoptic air flow and instrumental climate data from Braemar and Fort Augustus were analysed in relation to first ascents of ice climbs in the Cairngorms, and on Ben Nevis and Creag Meagaidh. Lagged weather variables were calculated and stepwise logistic regression was used to estimate optimum models for both areas. Significant variables are anticyclonicity, low minimum air temperature and northerly or easterly airflow (Cairngorms, P = 0.0006); and northerly or easterly airflow, low minimum air temperature and low precipitation (Ben Nevis and Creag Meagaidh, P < 0.0001). A five‐day cold spell is optimum for Ben Nevis and Creag Meagaidh. A week with relatively little precipitation is beneficial in both areas. Air flow direction is more influential than vorticity, the optimum predictors of ice conditions using synoptic data alone are a persistent easterly component (beneficial), and a persistent southerly and westerly component (detrimental), P < 0.0001.  相似文献   

10.
Rainfall during six days of monsoonal activity in the 1988/89 wet season is examined in terms of the influence of synoptic scale winds on mesoscale rainfall activity over the Townsville coastal plain (3450 km2). The resulting rainfall patterns. which were based on observations from a dense mesoscale network of 133 gauge points. are presented as isohyetal maps of twenty-four hour totals for each day in the study period. The study has shown that the distribution of rainfall is related to the influence of synoptic scale wind vectors, which provide upper level steering of convective activity. In addition. the interaction between local winds and synoptic circulation is deemed important for inducing convergence and precipitation. Rainfall generated is then directed by the prevailing upper synoptic flow. Orographic effects also appear to be significant, in that rainfall distribution tends to favour slopes on the windward side of the synoptic scale winds. The rainfall patterns described are probably typical of many of those that occurred throughout the 1988/89 wet season, due to the likely persistence of these mesoscale precipitation mechanisms. Similar mechanisms are also likely to occur over the study area in other wet seasons and elsewhere in the seasonally wet and dry tropics.  相似文献   

11.
This study assessed the influence of the Inter-Tropical Discontinuity (ITD) on inter-annual rainfall characteristics in Nigeria between 1970 and 2000. This involved determining the strength and direction of the relationships between the total annual rainfalls in the extreme southern and northern parts of the country and the total annual rainfalls during the period of the Little Dry Season in southwestern Nigeria, and the surface locations of the ITD over Nigeria and some other factors that may impact ITD characteristics (such as the pressure differences between Azores, Libyan and St. Helena anticyclones and the sea surface temperature of the Gulf of Guinea). Results indicate that although the surface location of the ITD significantly accounts for rainfall inter-annual variability in Nigeria, it does so in the northern part of the country only. Pressure differences between the various anticyclones were observed to be another significant factor influencing inter-annual rainfall variability in the north. However, the influence of the sea surface temperature of the Gulf of Guinea on the rainfall characteristics in the northern region is ill-defined. It was also noted that the only factor influencing inter-annual variability in the Little Dry Season rainfall in the southwest and the total annual rainfalls in the south is the sea surface temperature of the Gulf of Guinea. The results obtained indicate that the total annual rainfalls in the north have significant positive relationships with the surface location of the ITD but significant negative relationships with the pressure differences between the Azores, Libyan and St. Helena anticyclones. The Little Dry Season rainfalls and total annual rainfalls in the south have significant positive relationships with the sea surface temperature of the Gulf of Guinea.  相似文献   

12.
The normalised difference vegetation index (NDVI) has evolved as a primary tool for monitoring continental‐scale vegetation changes and interpreting the impact of short to long‐term climatic events on the biosphere. The objective of this research was to assess the nature of relationships between precipitation and vegetation condition, as measured by the satellite‐derived NDVI within South Australia. The correlation, timing and magnitude of the NDVI response to precipitation were examined for different vegetation formations within the State (forest, scrubland, shrubland, woodland and grassland). Results from this study indicate that there are strong relationships between precipitation and NDVI both spatially and temporally within South Australia. Differences in the timing of the NDVI response to precipitation were evident among the five vegetation formations. The most significant relationship between rainfall and NDVI was within the forest formation. Negative correlations between NDVI and precipitation events indicated that vegetation green‐up is a result of seasonal patterns in precipitation. Spatial patterns in the average NDVI over the study period closely resembled the boundaries of the five classified vegetation formations within South Australia. Spatial variability within the NDVI data set over the study period differed greatly between and within the vegetation formations examined depending on the location within the state. ACRONYMS AVHRR Advanced Very High Resolution Radiometer ENVSAEnvironments of South Australia EOS Terra‐Earth Observing System EVIEnhanced Vegetation Index MODIS Moderate Resolution Imaging Spectro‐radiometer MVC Maximum Value Composite NDVINormalised Difference Vegetation Index NIRNear Infra‐Red NOAANational Oceanic and Atmospheric Administration SPOT Systeme Pour l’Observation de la Terre  相似文献   

13.
尼罗河流域文明与地理环境变迁研究   总被引:1,自引:1,他引:0  
王会昌 《人文地理》1996,11(1):12-16
本文根据对尼罗河流域文明区地理环境变迁研究的结果,认为正是由于距今9000-4000年前亚非季风势力增强、季风雨量增加给尼罗河流域带来的湿润气候,为文明的形成和初步发展创造了优越的地理环境。因而尼罗河流域文明不仅仅是"尼罗河的赠礼",而应当更准确地说它是"季风雨的赠礼"。也正是由于季风雨的多寡在很大程度上制约着文明的盛衰,因此,由于从距今4000年前后开始的季风势力衰退和季风雨量锐减而导致的干旱化、沙漠化,则逐步吞噬了这一古老的文明。  相似文献   

14.
《Political Geography》2007,26(6):695-715
The conventional discourse relating climate change to conflict focuses on long term trends in temperature and precipitation that define ecosystems and their subsequent impact on access to renewable resources. Because these changes occur over long time periods they may not capture the proximate factors that trigger conflict. We estimate the impact of both long term trends in climate and short term climatic triggers on civil conflict onset in Sub-Saharan Africa. We find that both operationalizations have a significant impact. Climates more suitable for Eurasian agriculture are associated with a decreased likelihood of conflict, while freshwater resources per capita are positively associated with the likelihood of conflict. Moreover, positive changes in rainfall are associated with a decreased likelihood of conflict in the following year. We also assess the outlook for the future by analyzing simulated changes in precipitation means and variability over the period 2000–2099. We find few statistically significant, positive trends in our measure of interannual variability, suggesting that it is unlikely to be affected dramatically by expected changes in climate.  相似文献   

15.
Parks Canada began the Northern Satellite Monitoring Program in 1997, with the objective of tracking large‐scale vegetation variation in Canadian ecosystems and helping land managers to develop appropriate management practices in response to climate change. Under this program, a sequence of 10‐day composite Advanced Very High Resolution Radiometer (AVHRR)‐derived Normalized Difference Vegetation Index (NDVI) data from 1985 to 2007 was examined to study seasonal and inter‐annual relationships between vegetation and climate data over Canadian ecosystems using statistical and wavelet analysis. Statistical analysis showed that temperature was the principal driver for seasonal variability in greenness, explaining more than 70 percent of seasonal variation in vegetation for most Canadian ecozones. In comparison with temperature, the relationships between NDVI and precipitation were weaker but still significant. Maximum annual NDVI showed increasing trends in Canadian ecozones during the study period, although increasing rates were spatially heterogeneous. Wavelet analysis confirmed that inter‐annual variation in NDVI was different at two ecozones in Canada. NDVI variation in the Northern Arctic was significant at scales of 3–4 years from 1997 to 2001, which was associated with temperature and precipitation variation. Comparatively, NDVI variation in the Boreal Shield was significant at scales of 5–8 years from 1991 to 1999, but did not correspond with climate variation.  相似文献   

16.
降雨是陕西省榆林市榆阳区明长城的主要破坏因素之一。调查中发现,降雨对遗址破坏严重。为了研究降雨对遗址的破坏,在对遗址详细调查的基础上,结合遗址特征与遗址区降雨特点,并参考土壤侵蚀学等方面理论,分析了降雨对遗址的破坏形式及影响因素。结果表明,降雨对遗址的破坏形式可分为直接破坏和间接破坏两大类。其中,主要破坏形式为冲沟侵蚀、片流面蚀和雨蚀剥离。影响因素包括降雨特点、遗址形态、土的性质、植物生长状况和地幔层等,不同破坏形式的主要影响因素各有不同。本结果不仅丰富了降雨对土遗址破坏方面的研究,还为后续陕西榆阳区明长城保护加固措施的选择提供了依据。  相似文献   

17.
This article takes a fresh look at the decline of the Conservative Party in post‐war Scotland, a phenomenon that has provoked much debate. The analysis presented here is innovative in that it takes a regional approach, whereas other contributions to this field have tended to ignore the considerable regional diversity of Scottish political behaviour. By examining one particular region of Scotland – the rural north‐east – this article demonstrates that the Conservatives’ decline occurred at the hands of parties – the Liberals and the Scottish Nationalists – that did not brand themselves as left wing or right wing; the latter in particular eschewed conventional political labels. This marks another departure from the established literature, which has tended to discuss the decline in terms of the Conservative Party or the Scottish electorate moving ‘left’ or ‘right’. Furthermore, the article makes it clear that a serious decline befell the party between 1965 and 1979: before the advent of Thatcherism that has widely been held responsible for the Scottish Conservatives’ electoral woes. This analysis is conducted by examining the local press coverage of the region, as well as the national and regional records of the parties concerned. It therefore seeks to make a contribution to the wider study of post‐war British politics, by demonstrating the benefits of local and regional approaches in this period where they have been largely overlooked. This article demonstrates that even in the 1960s and 1970s, when politics seemed so nationally uniform, there is considerable diversity to be appreciated in different parts of the country.  相似文献   

18.
Forest transition theory and the reforesting of Scotland   总被引:1,自引:0,他引:1  
During the 20th century, the forest area in Scotland expanded threefold, after many centuries of decline. Similar trends of forest expansion following deforestation have operated in many other developed countries. The passage from net deforestation to net reforestation is defined as the forest transition, and over the last few years a body of theory relating to its drivers has evolved. The case of Scotland is considered in order to contribute to this growing body of theory.  相似文献   

19.
Accurate estimates of heavy rainfall probabilities reduce loss of life, property, and infrastructure failure resulting from flooding. NOAA's Atlas‐14 provides point‐based precipitation exceedance probability estimates for a range of durations and recurrence intervals. While it has been used as an engineering reference, Atlas‐14 does not provide direct estimates of areal rainfall totals which provide a better predictor of flooding that leads to infrastructure failure, and more relevant input for storm water or hydrologic modeling. This study produces heavy precipitation exceedance probability estimates based on basin‐level precipitation totals. We adapted a Generalized Extreme Value distribution to estimate Intensity‐Duration‐Frequency curves from annual maximum totals. The method exploits a high‐resolution precipitation data set and uses a bootstrapping approach to borrow spatially across homogeneous regions, substituting space in lieu of long‐time series. We compared area‐based estimates of 1‐, 2‐, and 4‐day annual maximum total probabilities against point‐based estimates at rain gauges within watersheds impacted by five recent extraordinary precipitation and flooding events. We found considerable differences between point‐based and area‐based estimates. It suggests that caveats are needed when using pointed‐based estimates to represent areal estimates as model inputs for the purpose of storm water management and flood risk assessment.  相似文献   

20.
This article examines the complex interactions between British national identity and the territorial identities of Northern Ireland and Scotland. We argue that the current literature on national identities in Britain misunderstands the nature of British identities in Northern Ireland and Scotland. Indeed, much of this literature wrongly defines Unionists in both of these areas. By examining the content of British national identity, a comparison of Scotland and Northern Ireland reveals that Unionism finds political significance through an ideological project committed to the Union. However, we also have to account for the differences in the Unionist ideology of Scotland and Northern Ireland. We argue that the institutional framework in which these identities and ideologies are exercised explains this variation. Overall, we argue that the debate on nationalism in the United Kingdom has not adequately shown how the integrative functions of British national identity can co-exist with the separatist nature of territorial national identity.  相似文献   

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