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121.
全球陆地年降水量与ENSO关系的初步研究 总被引:12,自引:0,他引:12
用全球陆地月降水资料(PREC/L),研究了1948-2000年期间的ENSO事件与全球陆地年降水量的关系,对全盛分析的结果进行了蒙特卡洛模拟经验。结果表明,暖事件年全球陆地年降水量大范围地明显减小,显著的地区是:赤道西太平洋区,中国的华北,赤道中美洲区,孟加拉湾北部及尼泊尔,东澳大利亚区,印度西部及巴基斯坦南部,勒拿河以东地区,西欧及南极的威尔克斯等区域。在暖事件年,陆地年降水量增加地区不多,主要是南美的智利和阿根廷,东非索马里,肯尼亚和坦桑亚,中东的土耳其,伊拉克及伊朗,北非的利比亚和阿尔及利亚,西南非的纳米比亚及非洲南部的博茨瓦纳和津巴布韦。统计检验表明,暖事件年全球陆地年降水量减少的面积比降水量增加的面积要大,而且更为显著,将本文结果与早期的研究结果进行了比较,研究还指出,ENSO的年代际变化对上述地区降水的年代际变化影响不明显。但是80年代以后的暖事件对东澳大利亚干旱,中国的华北的干旱的影响比80年代前的影响更大。 相似文献
122.
Takvor H. Soukissian Aristides M. Prospathopoulos Chrysoula Diamanti 《Journal of Atmospheric & Ocean Science》2002,8(2):163-189
In this paper, a statistical analysis on wind and wave buoy measurements and wind and wave model forecasts obtained during a two-year period (1999-2001) is presented with reference to four characteristic near-shore sites of the Aegean Sea. The measurements are a main product of the "POSEIDON" system aiming at the monitoring and forecasting of the state of the Greek seas, operated by the National Centre for Marine Research (NCMR). Although the two-year period is rather short for a thorough analysis of the local wind and wave climate, yet the obtained results, presented herein for the first time, reveal some interesting features of the corresponding wave and wind characteristics. Comparisons between the measurements and the forecast results are also performed at the locations under consideration. It is found that (i) wind speeds obtained from the POSEIDON weather forecasting system are, in general, in agreement with the measurements, except for high wind speeds which are systematically underestimated, (ii) the WAM model can successfully follow the monthly and over year trend of the evolution of wind and wave characteristics, but face significant problems for efficient sea-state forecasting. Finally, the overall pattern of the wind/wave climate for the entire Aegean Sea as obtained from the models is presented by means of the spatial distribution of the mean annual wind and sea-state intensity. 相似文献
123.
矿产勘查与评估的统计地球化学方法 总被引:1,自引:0,他引:1
统计地球化学在矿产勘查与评估中的应用,主要包括采术规则,临界品位计算,资源量/储量公式,边界品位确定,网度判别,矿床经济分类以及矿床开发风险等内容。 相似文献
124.
含水矿物在真空下的释Ar机制:Ar-Ar热年代学面临的新问题 总被引:2,自引:0,他引:2
地质体的实际情况、激光显微探针束研究、XRD和SEM观测以及真空加热下Ar的释放特征都表明体积扩散不是含水矿物在真空加热中释放Ar的唯一机制。在低温下 ,Ar的释放主要受由缺陷引起的短程扩散和体积扩散共同作用的多途径扩散机制制约 ;而在高温下 ,由于含水矿物在真空中不够稳定 ,Ar的释放受到脱羟基、脱氢、氧化反应、分层作用等造成的晶体结构改变的强烈影响。含水矿物在高温下的氧化分解会导致矿物中原始Ar浓度梯度的均一化 ,因而无法得到真实的Ar分布剖面 ,也无法据此计算矿物的封闭温度 ,并进而可能影响到ArAr年龄坪的地质意义。 相似文献
125.
安徽凤阳和张八岭地区含金石英脉的40Ar/39Ar年龄及其地质意义 总被引:3,自引:1,他引:3
用快中子活化法测定了安徽凤阳和张八岭地区朱顶、毛山和上成3个金矿床第一阶段晚期和第二阶段的含金石英脉,石英的阶段加热40Ar/39Ar坪年龄值域为(116.1±0.6~118.3±0.5)Ma,分别与其最小视年龄和等时线年龄接近.坪年龄、最小视年龄和等时线年龄3种年龄值域为(113.4±0.4~118.3±0.5)Ma,可以作为石英的形成年龄域. 根据含金石英脉和围岩的空间关系,该年龄值域作为石英脉金矿的形成年龄是合理可靠的.金矿床形成于早白垩世阿普特期,与此时郯庐断裂带略带右行走滑正断层活动一致. 相似文献
126.
The impact of Southern Oscillation on thecyclogenesis over the Bay of Bengal duringthe summer monsoon has been investigated.The analysis of correlation coefficients(CCs) between the frequency of monsoondepressions and the Southern OscillationIndex (SOI) reveals that more depressionsform during July and August of El Niñoyears. Due to this, the seasonal frequencyof monsoon depressions remains little higherduring El Niño epochs even though thecorrelations for June and September are notsignificant. The CCs for July and August aresignificant at the 99% level.The El Niño-Southern Oscillation (ENSO)is known to affect Indian MonsoonRainfall (IMR) adversely. The enhancedcyclogenesis over the Bay of Bengal duringJuly and August is an impact of ENSO whichneeds to be examined closely. Increasedcyclogenesis over the Bay of Bengal may bereducing the deficiency in IMR duringEl Niño years by producing more rainfallover the eastern parts of India duringJuly and August. Thus there is a considerablespatial variation in the impact of ENSOon the monsoon rainfall over India and El Niñoneed not necessarily imply a monsoonfailure everywhere in India.The area of formation of monsoon depressionsshifts eastward during El Niño years.Warmer sea surface temperature (SST) anomaliesprevail over northwest and adjoiningwestcentral Bay of Bengal during premonsoon andmonsoon seasons of El Niño years.May minus March SOI can provide useful predictionsof monsoon depression frequencyduring July and August. 相似文献
127.
Identifying and quantifying urban recharge: a review 总被引:12,自引:1,他引:12
David N. Lerner 《Hydrogeology Journal》2002,10(1):143-152
The sources of and pathways for groundwater recharge in urban areas are more numerous and complex than in rural environments.
Buildings, roads, and other surface infrastructure combine with man-made drainage networks to change the pathways for precipitation.
Some direct recharge is lost, but additional recharge can occur from storm drainage systems. Large amounts of water are imported
into most cities for supply, distributed through underground pipes, and collected again in sewers or septic tanks. The leaks
from these pipe networks often provide substantial recharge. Sources of recharge in urban areas are identified through piezometry,
chemical signatures, and water balances. All three approaches have problems. Recharge is quantified either by individual components
(direct recharge, water-mains leakage, septic tanks, etc.) or holistically. Working with individual components requires large
amounts of data, much of which is uncertain and is likely to lead to large uncertainties in the final result. Recommended
holistic approaches include the use of groundwater modelling and solute balances, where various types of data are integrated.
Urban recharge remains an under-researched topic, with few high-quality case studies reported in the literature.
Electronic Publication 相似文献
128.
Lake Teletskoye occupies a narrow graben located in the northwestern sector of the Altai fold belt in South Siberia. The lake basin is thought to have formed during the Pleistocene as a distant result of the Cenozoic collision of India and Eurasia that caused a tectonic reactivation of the Palaeozoic Gorny–Altai (GA) and West Sayan (WS) blocks.The present work reports of a pilot fission-track study performed on 13 apatite separates collected from rocks that were sampled along two profiles in close proximity of the lake. The age–length data and AFT thermochronological modelling reveal two important phases of cooling in the Altai Mountains, a first one during the Late Jurassic–Early Cretaceous and a second one that started in the Miocene–Pliocene and that persists until today. The first event is interpreted to result from uplift-induced denudation probably related to the closure of the Mongol–Okhotsk Ocean; the second event can be linked to the young Cenozoic movements that lie at the origin of the formation of the Lake Teletskoye basin. 相似文献
129.
A. K. Varma R. M. Gairola A. K. Mathur B. S. Gohil Vijay K. Agarwal 《Journal of Earth System Science》2002,111(3):247-256
In this paper, MSMR geophysical products like Integrated Water Vapour (IWV), Ocean Surface Wind Speed (OWS) and Cloud Liquid
Water (CLW) in different grids of 50, 75 and 150 kms are compared with similar products available from other satellites like
DMSP-SSM/I and TRMMTMI. MSMR derived IWV, OWS and CLW compare well with SSM/I and TMI finished products. Comparison of MSMR
derived CLW with that derived from TMI and SSM/I is relatively in less agreement. This is possibly due to the use of 37 GHz
in SSM/I and TMI that is highly sensitive to CLW, while 37 GHz channels are not available on MSMR. Monthly comparison of MSMR
geophysical products with those from TMI is all carried out for climatological purpose. The monthly comparisons were much
better compared to instantaneous comparisons. In this paper, details of the data analysis and comparison results are presented.
The usefulness of the MSMR vis-à-vis other sensors is also discussed. 相似文献
130.
Antonio Longinelli Paola IacuminMichele Ramigni 《Earth and Planetary Science Letters》2002,203(1):445-459
Belemnite guards of Cretaceous and Jurassic age were found to contain varying amounts of quartz deposited both on the external surface and inside the rostrum. The oxygen isotopic composition of coexisting carbonate, quartz and phosphate from the same rostrum was measured according to well-established techniques. None of these compounds showed isotopic values in equilibrium with one another. Assuming δ18O values of the diagenetic water within the range of meteoric waters, the δ18O(SiO2) yield temperatures in agreement with the apparent secondary origin of this phase. The δ18O(CO32−) range, with a certain continuity, between −10.8 and +0.97 PDB-1 with most of the intermediate values being within the range of the carbonate isotopic values of Mesozoic fossils. The most positive isotopic results obtained from phosphate are close to +23/+24‰ (V-SMOW). They can hardly be related to a secondary origin of the phosphate, or to the presence of diagenetic effects, since these results are among the most positive ever measured on phosphate. As far as we know there is no widespread diagenetic process determining an 18O enrichment of phosphate. The very low concentration of phosphate did not allow the determination of its mineralogical composition. All the available δ18O(PO43−) values from belemnite and non-belemnite fossils of marine origin of Tertiary and Mesozoic age are reported along with the newly measured belemnites. The following conclusions may be drawn from the data reported: (1) the pristine oxygen isotope composition of fossil marine organisms (either carbonate or phosphate) may easily undergo fairly large changes because of oxygen isotope exchange processes with diagenetic water; this process is apparent even in the case of geologically recent fossils; (2) the δ18O(PO43−) of belemnite rostra seems to be, at least in the case of the most positive results, in isotopic equilibrium with environmental water because of the similarity between the results from Cretaceous belemnites and the results from Cretaceous and Lower Tertiary pelecypods and fish teeth; 3) if so, the only feasible interpretation that can be suggested for the 18O enriched data is the possibility of a relatively large variation of the oxygen isotopic composition of ocean paleowater from Jurassic to recent time. 相似文献