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81.
Predicting tropical cyclone(TC) genesis is of great societal importance but scientifically challenging. It requires fineresolution coupled models that properly represent air-sea interactions in the atmospheric responses to local warm sea surface temperatures and feedbacks, with aid from coherent coupled initialization. This study uses three sets of highresolution regional coupled models(RCMs) covering the Asia-Pacific(AP) region initialized with local observations and dynamically downscaled coupled data assimilation to evaluate the predictability of TC genesis in the West Pacific. The APRCMs consist of three sets of high-resolution configurations of the Weather Research and Forecasting-Regional Ocean Model System(WRF-ROMS): 27-km WRF with 9-km ROMS, and 9-km WRF with 3-km ROMS. In this study, a 9-km WRF with 9-km ROMS coupled model system is also used in a case test for the predictability of TC genesis. Since the local sea surface temperatures and wind shear conditions that favor TC formation are better resolved, the enhanced-resolution coupled model tends to improve the predictability of TC genesis, which could be further improved by improving planetary boundary layer physics, thus resolving better air-sea and air-land interactions.  相似文献   
82.
83.
景号然  郑伟  刘宗庆  谢晓林  彭涛 《气象》2020,46(2):278-282
采用航天飞机雷达地形测绘使命(SRTM)高程数据对天气雷达净空环境进行评估,可有效提高雷达选址评估效率。利用人工测量数据和SRTM数据进行天气雷达净空环境评估对比试验,结果表明基于该数据的天气雷达净空环境评估算法总体与人工测量方法具有较好的一致性。采用方位矫正和距离矫正算法后,基于该数据的天气雷达净空环境评估算法精度明显提高。  相似文献   
84.
张岩  方维萱  徐林刚  陈文  张志炳  叶会寿  刘丽红  王文浩  赵亮亮  吴皓然 《地质论评》2024,70(1):2024010014-2024010014
对氧化—还原敏感元素和生命必需元素地球化学性质和相关沉积矿产形成机制及其时空分布特征的分析、总结和归纳,有助于对古海洋环境演化与相关沉积矿产形成关系的深入认识,这对沉积矿床学理论的发展具有重要意义。新元古代南华纪—早古生代早志留世,扬子板块周缘黑色岩系中依次沉积了举世瞩目的南华纪锰矿、震旦纪—早寒武世沉积磷块岩、早寒武世重晶石矿、镍—钼—钴多金属矿、钒矿和早志留世铀矿的完整沉积矿床系列,不同时代地层、同一时代不同沉积环境地层赋存不同类型的沉积矿产,有必要对其成矿机理进行系统研究、总结和归纳。本文在对氧化—还原敏感金属元素、生命必需元素和海底热液元素等元素地球化学性质综述的基础上,兼论了它们在结合黄铁矿矿物学对氧化—还原环境、生物生产力和盆地限制性分析方面具体作用;进一步结合新元古代—早古生代扬子板块古环境演化特征,对扬子板块周缘特定时代中特定沉积矿产的分布、成因机理进行分析、总结和归纳;最终得出扬子板块周缘相关沉积矿产,是在全球氧化事件、冰期—间冰期、Rodina大陆裂解大背景下,海洋中成矿金属元素得到长期积累,在特定时代区域性海水—海底热液—生物作用(根据不同矿种各有侧重)影响下,在相关重要元素地球化学性质的控制下、局部区域特殊氧化—还原环境的控制下形成的特定矿产的初步认识。最后,结合相关沉积矿床研究中存在的问题,提出下一步解决方案与展望。  相似文献   
85.
秦岭伏牛山构造带的矿物岩石学特征与流变学分析   总被引:1,自引:0,他引:1       下载免费PDF全文
本文通过对伏牛山构造带岩石的矿物岩石学、石英重结晶型式、石英分维值和有限应变等特征分析研究,认为伏牛山构造带的变质-变形深受洛南-栾川断裂带的影响,其变化有明显的规律性,从断裂带往北岩石从糜棱岩依次过渡为片岩-片麻岩-花岗岩原岩.构造带内发育多种糜棱岩,岩石变形强烈,远离构造带岩石的变形逐渐变弱.从构造带往北,石英的重...  相似文献   
86.
相对于我国各行业抗震规范反应谱下降段呈现的多样性,欧美规范谱基于理想化反应谱模型,其长周期下降段的规定形式统一,且由第二特征周期TD确定.基于理想化反应谱模型,TD的确定与位移谱形态、"结构所需周期范围"等概念相关.基于我国区划图研究中大量采用NGA数据库的地震动记录及以地震动峰值加速度分区值表达地震强度的现状,以理想...  相似文献   
87.
In this study, we present zircon U-Pb ages, whole-rock geochemical data and Hf isotopic compositions for the Meiguifeng and Arxan plutons in Xing'an Massif, Great Xing'an Range, which can provide important information in deciphering both Mesozoic magmatism and tectonic evolution of NE China. The zircon U-Pb dating results indicate that alkali feldspar granite from Meiguifeng pluton was emplaced at ~145 to 137 Ma, and granite porphyry of Arxan pluton was formed at ~129 Ma. The Meiguifeng and Arxan plutons have similar geochemical features, which are characterized by high silica, total alkalis, differentiation index, with low P_2O_5, CaO, MgO, TFe_2O_3 contents. They belong to high-K calc-alkaline series, and show weakly peraluminous characteristics. The Meiguifeng and Arxan plutons are both enriched in LREEs and LILEs(e.g., Rb, Th, U and K), and depleted in HREEs and HFSEs(e.g., Nb, Ta and Ti). Combined with the petrological and geochemical features, the Meiguifeng and Arxan plutons show highly fractionated I-type granite affinity. Moreover, the Meiguifeng and Arxan plutons may share a common or similar magma source, and they were probably generated by partial melting of Neoproterozoic high-K basaltic crust. Meanwhile, plagioclase, K-feldspar, biotite, apatite, monazite, allanite and Ti-bearing phases fractionated from the magma during formation of Meiguifeng and Arxan plutons. Combined with spatial distribution and temporal evolution, we assume that the generation of Early Cretaceous Meiguifeng and Arxan plutons in Great Xing'an Range was closely related to the break-off of Mudanjiang oceanic plate. Furthermore, the Mudanjiang Ocean was probably a branch of Paleo-Pacific Ocean.  相似文献   
88.
One of the fundamental questions concerning the nature and prediction of the oceanic states in the equatorial eastern Pacific is how the turnabout from a cold water state (La Ni?na) to a warm water state (El Ni?no) takes place, and vice versa. Recent studies show that this turnabout is directly linked to the interannual thermocline variations in the tropical Pacific Ocean basin. An index, as an indicator and precursor to describe interannual thermocline variations and the turnabout of oceanic states in our previous paper (Qian and Hu, 2005), is also used in this study. The index, which shows the maximum subsurface temperature anomaly (MSTA), is derived from the monthly 21-year (1980–2000) expendable XBT dataset in the present study. Results show that the MSTA can be used as a precursor for the occurrences of El Ni?no (or La Ni?na) events. The subsequent analyses of the MSTA propagations in the tropical Pacific suggest a one-year potential predictability for El Ni?no and La Ni?na events by identifying ocean temperature anomalies in the thermocline of the western Pacific Ocean. It also suggests that a closed route cycle with the strongest signal propagation is identified only in the tropical North Pacific Ocean. A positive (or negative) MSTA signal may travel from the western equatorial Pacific to the eastern equatorial Pacific with the strongest signal along the equator. This signal turns northward along the tropical eastern boundary of the basin and then moves westward along the north side of off-equator around 16N. Finally, the signal returns toward the equator along the western boundary of the basin. The turnabout time from an El Ni?no event to a La Ni?na event in the eastern equatorial Pacific depends critically on the speed of the signal traveling along the closed route, and it usually needs about 4 years. This finding may help to predict the occurrence of the El Ni?no or La Ni?na event at least one year in advance.  相似文献   
89.
陈轶林  孔令明  梁浩然 《地质论评》2023,69(3):1019-1030
有机碳含量(TOC)是页岩气资源评价与预测选区的关键指标之一,测井预测是实现单井TOC连续识别的重要手段,本次研究拟揭示各类预测方法在下古生界海相页岩中的预测效果。本次以川南长宁地区龙一段黑色页岩为对象,尝试采用多类预测方法(ΔLogR法及其改进方法、多元线性回归法与神经网络法)与不同的研究尺度(全段或分层)建立TOC测井预测模型,并对不同方法的预测效果进行深入探讨。研究表明,各方法预测效果差异较大,适用性各不相同。整体而言,多元线性回归法与BP神经网络法在研究区的预测效果均优于ΔLogR法及其改进方法。笔者等研究提出多元线性回归法对研究区TOC高值段的预测效果更佳,而神经网络法对TOC低值段的预测精度更高。本次研究根据龙一段各亚段有机质分布特征与测井响应特征的差异,提出通过“精细分层与最优方法匹配”的方式,因地制宜地选择相应的方法进行TOC测井预测。针对龙一1a-c与龙一1d-龙一2,分别采用多元线性回归法与BP神经网络法进行分层精细建模,并获得了最佳的预测效果,不仅预测精度...  相似文献   
90.
Carbonate precipitation and hydrothermal reaction are the two major processes that remove Mg from seawater. Mg isotopes are significantly (up to 5‰) fractionated during carbonate precipitation by preferential incorporation of 24Mg, while hydrothermal reactions are associated with negligible Mg isotope fractionation by preferential sequestration of 26Mg. Thus, the marine Mg cycle could be reflected by seawater Mg isotopic composition (δ26Mgsw), which might be recorded in marine carbonate. However, carbonates are both texturally and compositionally heterogeneous, and it is unclear which carbonate component is the most reliable for reconstructing δ26Mgsw. In this study, we measured Mg isotopic compositions of limestone samples collected from the early Carboniferous Huangjin Formation in South China. Based on petrographic studies, four carbonate components were recognized: micrite, marine cement, brachiopod shell, and mixture. The four components had distinct δ26Mg: (1) micrite samples ranged from ?2.86‰ to ?2.97‰; (2) pure marine cements varied from ?3.40‰ to ?3.54‰, while impure cement samples containing small amount of Rugosa coral skeletons showed a wider range (?3.27‰ to ?3.75‰); (3) values for the mixture component were ?3.17‰ and ?3.49‰; and (4) brachiopod shells ranged from ?2.20‰ to ?3.07‰, with the thickened hinge area enriched in 24Mg. Due to having multiple carbonate sources, neither the micrite nor the mixture component could be used to reconstruct δ26Mgsw. In addition, the marine cement was homogenous in Mg isotopes, but lacking the fractionation by inorganic carbonate precipitation that is prerequisite for the accurate determination of δ26Mgsw. Furthermore, brachiopod shells had heterogeneous C and Mg isotopes, suggesting a significant vital effect during growth. Overall, the heterogeneous δ26Mg of the Huangjin limestone makes it difficult to reconstruct δ26Mgsw using bulk carbonate/calcareous sediments. Finally, δ26Mgsw was only slightly affected by the faunal composition of carbonate-secreting organisms, even though biogenic carbonate accounts for more than 90% of marine carbonate production in Phanerozoic oceans and there is a wide range (0.2‰–4.8‰) of fractionation during biogenic carbonate formation.  相似文献   
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