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991.
东亚高空急流(简称急流)对夏季东亚地区的天气和气候有着重要影响。本文利用CMIP5的历史气候模拟试验和RCP8.5路径下的未来气候变化预估试验数据,预估了急流在6个全球变暖阈值(1.5℃,2.0℃,2.5℃,3.0℃,3.5℃和4.0℃)下相对于当代气候的变化情况。结果表明东亚高空西风在1.5℃阈值下略微减弱。在2.0℃阈值下,西风在急流轴(约40°N)南侧增强,北侧减弱。这种变化趋势在2.5℃和更高的变暖阈值下愈加明显,使急流轴逐渐向南移动,但急流强度变化不大。研究表明,在急流的入口和出口区,对流层中上层大气升温速度相对较慢,导致在急流轴南(北)侧出现向南(北)的负(正)经向温度梯度,使西风在南(北)侧增强(减弱). 相似文献
992.
993.
We report results of our optical photometric observations of ten gamma-ray loud blazers, namely: 0219+428 (3C66A), PKS 0420-014 (OA 129), S5 0716+714, 0754+100 (OI 090.4), 0827+243 (OJ248), 1652+398 (Mrk 501), 2200+420 (BL Lacertae), 2230+114 (CTA 102), 2251+158 (3C 454.3) and 2344+514. The observations were carried out in September-October, 2000 using the 70 cm optical telescope at Abstumani Observatory, Georgia. We found intra-day variations in 0420-014, S5 0716+714, BL Lacertae and CTA 102. A variation of 0.3 magnitude over a time scale of about 3 hours was observed in the R passband in BL Lacertae on JD 2451827. We did not detect any variation in 3C 66A, Mrk 501, or 3C 454.3 during our observations. Nor did we detect any clear evidence of variation in 1ES 2344+514 during our two weeks' observing run of the TeV gamma-ray source. 相似文献
994.
The stochastic–conceptual rainfall–runoff simulator (SCRRS) developed by R. A. Freeze in 1980 was used in this study to demonstrate quantitatively the interplay of the factors that control the occurrence of overland flow by the Horton and Dunne mechanisms. The simulation domain and input data for the SCRRS simulations reported here were abstracted from the R‐5 catchment (Chickasha, OK) data sets. The results illustrate that the identification of a dominant hydrological response process may not be as simple as a singular Horton or Dunne characterization. The SCRRS simulations show that the Horton and Dunne processes can (i) occur simultaneously at different locations during a given rainfall event, (ii) change from one process to the other with time depending on the characteristics of the rainfall event, and (iii) be strongly dependent on the initial conditions. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
995.
Anne Hormes Maarten Blaauw Svein Olaf Dahl Atle Nesje Goran Possnert 《Quaternary Geochronology》2009,4(4):267-277
The problem of insufficient age-control limits the utilisation of the 8.2 ka BP event for modelling freshwater forcing in climate change studies. High-resolution radiocarbon dates, magnetic susceptibility and lithostratigraphic evidence from a lake sediment core from Nedre Hervavatnet located at Sygnefjell in western Norway provide a record of the early Holocene. We use the method of radiocarbon wiggle-match dating of the lake sediments using the non-linear relationship between the 14C calibration curve and the consecutive accumulation order of the sample series in order to build a high-resolution age-model. The timing and duration of Holocene environmental changes is estimated using 38 AMS radiocarbon dates on terrestrial macrofossils, insects and chironomids covering the time period from 9750 to 1180 cal BP. Chironomids, Salix and Betula leaves produce the most consistent results. Sedimentological and physical properties of the core suggest that three meltwater events with high sedimentation rates are superimposed on a long-term trend with glacier retreat between 9750 and 8000 cal BP. The lake sediment sequence of Nedre Hervavatnet demonstrates the following: only a reliable high-resolution geochronology based on carefully selected terrestrial macrofossils allows the reconstruction of a more refined and complex environmental change history before and during the 8.2 ka event. 相似文献
996.
Al2SiO5 reaction textures in aluminous schist and quartziteof the northern Picuris range, north-central New Mexico, recorda paragenetic sequence of kyanite to sillimanite to andalusite,consistent with a clockwise PT loop, with minor decompressionnear the Al2SiO5 triple-point. Peak metamorphic temperaturesare estimated at 510525°C, at 4·04·2kbar. Kyanite and fibrolite are strongly deformed; some prismaticsillimanite, and all andalusite are relatively undeformed. Monaziteoccurs as inclusions within kyanite, mats of sillimanite andcentimetre-scale porphyroblasts of andalusite, and is typicallyaligned subparallel to the dominant regional foliation (S0/S1or S2) and extension lineation (L1). Back-scatter electron imagesand X-ray maps of monazite reveal distinct core, intermediateand rim compositional domains. Monazitexenotime thermometryfrom the intermediate and rim domains yields temperatures of405470°C (±50°C) and 500520°C(±50°C), respectively, consistent with the progradeto peak metamorphic growth of monazite. In situ, ion microprobeanalyses from five monazites yield an upper intercept age of1417 ± 9 Ma. Near-concordant to concordant analyses yield207Pb206Pb ages from 1434 ± 12 Ma (core) to 1390± 20 Ma (rim). We find no evidence of older regionalmetamorphism related to the 1650 Ma Mazatzal Orogeny. KEY WORDS: Al2SiO5; metamorphism; monazite; thermochronometry; triple-point 相似文献
997.
藏北羌塘盆地独雪山地区,在原先认为不整合于早侏罗世火山岩系之上的“中侏罗统雀莫错组”中, 新近发现了一套早侏罗世淡水双壳类祁阳蚌(Qiyangia)组合,表明羌北盆地存在早侏罗世沉积地层,其为一套海陆交互相沉积的粗碎屑岩→灰岩→细碎屑岩夹灰岩,下侏罗统与中侏罗统为连续沉积。据此资料,该区侏罗系目前采用的岩石地层单位系统及地层的对比认识存有问题,文章对此套早侏罗世沉积的岩石地层划分方案进行了讨论, 指出雁石坪地区的侏罗系岩石地层系统作为等时的地层单位运用于羌北盆地北西部并不适宜,羌北盆地已有的地层系统格架有必要重新认识。 相似文献
998.
999.
Asghar ALI 《《地质学报》英文版》2012,86(5):1241-1250
Constraints from P-T pseudosections (MnNCKFMASH system), foliation intersection/inflection axes preserved in porphyroblasts (FIAs), mineral assemblages and textural relationships for rocks containing all three Al2SiO5 polymorphs indicate a kyanite→ andalusite→ sillimanite sequential formation at different times rather than stable coexistence at the Al2SiO5 triple point. All three Al2SiO5 polymorphs grew in the Chl, Bt, Ms, Grt, St, Pl and Crd bearing Ordovician Clayhole Schist in Balcooma, northeastern Australia separately along a looped P-T-t-D path that swaps from clockwise to anticlockwise in the tectono-metamorphic history of the region. Kyanite grew during crustal thickening in an Early Silurian Orogenic event followed by decompression/heating, andalusite and fibrolitic sillimanite growth during Early Devonian exhumation. 相似文献
1000.
在大地电磁法勘探中,为了快速从工区项目众多文件中选出与某一特定点位具有重叠采集时间的点位文件,并进行远参考处理或便捷地读取一些实测点位信息,常用的方法是利用SSMT2000处理软件,找出具有重叠采集时间的点位文件和从处理输出结果EDI文件中,逐一读取相应参数。如果采用编程的思想直接从原始TBL参数文件中读取相应参数,便可快速达到此目的。鉴于MATLAB语言最近在地学领域内越来越被广泛使用,这里利用MATLAB平台对V5—2000大地电磁测深仪TBL参数文件进行了分析,并给出相应读取程序,在提取所需信息后可以快速提高此类问题的工作效率。 相似文献