Regional m_b:M_s, Lg/Pg amplitude ratios and Lg spectral ratios as criteria for distinguishing between earthquakes and explosions: a theoretical study     

R. C. Lilwall 《Geophysical Journal International》1988,93(1):137-147

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上海地区春季最高气温预报失败案例分析     

孙敏  袁慧玲  杜予罡 《气象》2018,44(1):65-79

本文分析了2015年3月17—18日上海地区连续两天发生最高气温预报失误的天气背景,并使用当日实况观测和业务预报使用的数值模式资料,剖析预报失败的原因,分析表明:对天空状况的误判是导致17日预报失败的主要原因,且东南风预报偏强更进一步增大了预报误差;冷空气影响时间的判断失误是导致18日预报失败的主要原因。从模式预报的实时检验、预报的跳跃性和不确定性角度分析了预报中存在的问题:预报员应重视本地和上游实况,从传统对单一确定性模式预报的依赖向多模式多起报时次及能提供概率预报和不确定性信息的业务集合预报的分析思路转型。此外,还需加强对集合预报的系统性检验、评估及数值预报释用产品的开发,增加包含不确定性信息的公众天气预报发布形式。  相似文献   

一种2 m温度误差订正方法在复杂地形区数值预报中的应用          下载免费PDF全文

赵滨  张博 《大气科学学报》2018,41(5):657-667

利用模式三维预报变量,结合地面要素预报产品,采用2 m温度三维插值方法进行地形订正,以确保预报与观测三维空间上的一致性,在地形订正基础上,利用历史月均预报误差作为参考误差,剔除模式系统性误差,获取具备日变化特征的预报产品。基于陕西地区复杂地形条件下的典型观测站点,利用2016年8月28日48 h预报个例进行对比分析发现,三维插值方法有效改善了地形差异引起的评估误导问题,但无法改进模式预报的日变化趋势,进一步采用系统性误差订正后,日变化特征明显改善,特别是前24 h预报效果体现出与实况良好的一致性及更佳的预报技巧。通过2016年夏季统计评估表明,误差订正后的2 m温度预报产品有效改善了周期性误差振荡,均方根误差稳定在2 K左右,显示出明显的改进优势。  相似文献   

新矿物丁道衡矿-（Ce）：珀硅钛铈矿的同质多象体和硅钛铈矿亚族C（1）位上的钛类似矿物   总被引：1，自引：1，他引：0  

徐金沙  杨光明  李国武  邬志亮  沈敢富 《矿物学报》2008,28(3)

丁道衡矿-(Ce):(Ce,La)4Fe2 (Ti,Fe2 ,Mg,Fe3 )2Ti2Si4O22,理想的结构化学式Ce2Ce2Fe2 Ti2Ti2Si4O22单斜晶系,α=1.34656(15)nm,b=0.57356(6)nm,c=1.10977(12)nm,β=100.636(2)°,V=0.84239(46)nm3,空间群P21/a(假C2/m),Z=2.作为硅钛铈矿(chevkinite)族矿物的新成员,它产于举世闻名的白云鄂博铁.稀土.铌矿床镁夕卡岩中,多数单晶体长0.2～1.0 cm,最大者长大于1.5 cm.共生矿物有透辉石、透闪石、钠透闪石、褐帘石-(Ce)、磁铁矿、尖晶石、烧绿石、氟金云母、氟磷灰石、石英和萤石等.矿物具有褐色条痕和半金属一金属光泽的黑色,其褐黑色碎片半透明.性脆、具有贝壳状断口、无解理和裂开.显微硬度(VHN25g)为606.0～717.4 kg/mm/12(相当于摩氏硬度约5.9).矿物实测密度4.83(7)g/cm3,计算密度值4.88(0)g/cm3.丁道衡矿-(ce)的反射色为带灰色的浅黄色,多色性为不同色调的灰色.平均反射率(λ=589nm)为11.4%～12.5%.矿物为二轴晶负光性.作过结构精测的丁道衡矿-(Ce)晶体的电子探针测值:SiO2:19.29,TiO2:18.26,A12O3:0.04,FeO:8.49,Fe2O3,:1.67,ThO2:0.16,MgO:1.32,CaO:2.17,Nb2O5:0.47,Ta2O5:0.00,La2O3:19.53,Ce2O3:28.08,Y2O3:0.00,Na1O:0.01,总量99.46%;其中Fe3 /Fe2 的比值依穆斯堡尔谱换算.根据结构精测每个单位分子式中O=22和C(1)位上Ti优先占位,计算的矿物晶体化学式为(Ce2.13,La1.49Ca0.48Th0 01)Σ4.11Fe2 (Tin0.88Fe2 0.47Mg0.41 Fe0.0)Σ2.03(Ti1.96Nb0 04)Σ2.00(Si2O7)2O3.分别用P21/a和C2/m对丁道衡矿-(Ce)的晶体结构作了精测.结果表明,丁道衡矿-(Ce)的真空间群是P20/a.换言之,它才是真正珀硅钛铈矿[perrierite-(Ce)]的同质多象体.显而易见,硅钛铈矿族矿物既可以有P21/a空间群,又可以有C2/m空间群.  相似文献   

北京西北活动构造定量资料与未来强震地点的讨论   总被引：9，自引：2，他引：9       下载免费PDF全文

冉勇康  陈立春  徐锡伟 《地震学报》2001,23(5):502-513

通过阐述北京西北的活动构造定量数据及其精度，用确定性方法、概率方法和综合评分方法，通过排队，比较出北京西北及邻近地区未来强震可能发生的地点，讨论预测结果中存在的一些问题．结果显示，未来强震最危险的断裂段为:阳原盆地南缘断裂B段和A段、延矾盆地的燕水段、宣化盆地南缘断裂、怀安镇南缘断裂东段和阳高——天镇北缘断裂东段等段落．亦即阳原-深井盆地为最危险区；天镇-怀安镇-宣化盆地为次危险区；万全-张家口和蔚县东北-矾山西南为更次危险区．   相似文献   

Timing of low-temperature metamorphism and cooling of the Paleozoic and Mesozoic formations of the Bükkium,innermost Western Carpathians,Hungary     

P. Árkai  K. Balogh  I. Dunkl 《International Journal of Earth Sciences》1995,84(2):334-344

K-Ar ages of illite-muscovite and fission track ages of zircon and apatite were determined from various lithotypes of the Bükkium, which forms the innermost segment of the Western Carpathians. The stratigraphic ages of these Dinaric type formations cover a wide range from the Late Ordovician up to the Late Jurassic. The grade of the orogenic dynamo-thermal metamorphism varies from the late diagenetic zone through the anchizone up to the epizone (chlorite, maximally biotite isograd of the greenschist facies). The K-Ar system of the illite-muscovite in the < 2 m grain-size fraction approached equilibrium only in epizonal and high-temperature anchizonal conditions. The orogenic metamorphism culminated between the eo-Hellenic (160-120 Ma) phase connected to the beginning of the subduction in the Dinarides, and the Austrian (100-95 Ma) phase characterized by compressional crustal thickening. No isotope geochronological evidence was found for proving any Hercynian recrystallization. The stability field of fission tracks in zircon was approached using the thermal histories of the different tectonic units. A temperature less than 250°C and effective heating time of 20–30 Ma had only negligible effects on the tracks, whereas total annealing was reached between 250 and 300°C. Apatite fission track ages from the Paleozoic and Mesozoic formations show that the uplift of the Bükk Mountains occurred only in the Tertiary (not earlier than ca. 40 Ma ago). Thermal modeling based on apatite fission track length spectra and preserved Paleogene sediment thickness data proved that the Late Neogene burial of the recently exhumed plateau of the Bükk Mountains exceeded 1 km.  相似文献   

Quaternary changes in delivery and accumulation of organic matter in sediments of Lake Biwa, Japan     

Philip A. Meyers  Keiji Takemura 《Journal of Paleolimnology》1997,18(3):211-218

A 911-m-long sediment core from Lake Biwa, Japan, provides a record of organic matter delivery and accumulation in this large lake during a succession of tectonic and climatic changes dating back to the latest Pliocene. Sediments deposited since 430 ky are profundal; older sediments vary in setting between shallow-water and fluviodeltaic conditions, with occasional deep-water intervals. C/N ratios identify algal production as the dominant source of organic matter throughout the core, although the proportion of land-derived contributions episodically increases in the fluviodeltaic and shallow-water sediments. Rates of organic matter delivery and burial in lake sediments change in response to glacial-interglacial climate changes over the past 430 ky. Sediments deposited during interglacial intervals have organic carbon mass accumulation rates up to 9 times greater than those from glacial intervals, reflecting interglacial climates that were wetter than glacial climates. Algal production of organic matter increased during interglacial times because of greater wash-in of soil nutrients, and organic matter preservation was enhanced because of faster sedimentation rates.  相似文献   

半干旱半湿润地区洪水预报模型适用性研究   总被引：1，自引：0，他引：1       下载免费PDF全文

刘郁  赵兰兰  马丁 《水文》2016,36(1):32-36

针对半干旱半湿润地区的流域特性和产汇流特点,比较了河北雨洪模型和新安江模型的模型原理和模型特性,以滦河支流老牛河流域为例,开展了洪水预报适用性研究。结果表明,河北雨洪模型的预报精度较高,更适用于半干旱半湿润地区的洪水预报。  相似文献   

Mapping rice-fallow cropland areas for short-season grain legumes intensification in South Asia using MODIS 250 m time-series data     

Murali Krishna Gumma  Prasad S. Thenkabail  Pardharsadhi Teluguntla  Mahesh N. Rao  Irshad A. Mohammed  Anthony M. Whitbread 《International Journal of Digital Earth》2016,9(10):981-1003

The goal of this study was to map rainfed and irrigated rice-fallow cropland areas across South Asia, using MODIS 250?m time-series data and identify where the farming system may be intensified by the inclusion of a short-season crop during the fallow period. Rice-fallow cropland areas are those areas where rice is grown during the kharif growing season (June–October), followed by a fallow during the rabi season (November–February). These cropland areas are not suitable for growing rabi-season rice due to their high water needs, but are suitable for a short -season (≤3 months), low water-consuming grain legumes such as chickpea (Cicer arietinum L.), black gram, green gram, and lentils. Intensification (double-cropping) in this manner can improve smallholder farmer’s incomes and soil health via rich nitrogen-fixation legume crops as well as address food security challenges of ballooning populations without having to expand croplands. Several grain legumes, primarily chickpea, are increasingly grown across Asia as a source of income for smallholder farmers and at the same time providing rich and cheap source of protein that can improve the nutritional quality of diets in the region. The suitability of rainfed and irrigated rice-fallow croplands for grain legume cultivation across South Asia were defined by these identifiers: (a) rice crop is grown during the primary (kharif) crop growing season or during the north-west monsoon season (June–October); (b) same croplands are left fallow during the second (rabi) season or during the south-east monsoon season (November–February); and (c) ability to support low water-consuming, short-growing season (≤3 months) grain legumes (chickpea, black gram, green gram, and lentils) during rabi season. Existing irrigated or rainfed crops such as rice or wheat that were grown during kharif were not considered suitable for growing during the rabi season, because the moisture/water demand of these crops is too high. The study established cropland classes based on the every 16-day 250?m normalized difference vegetation index (NDVI) time series for one year (June 2010–May 2011) of Moderate Resolution Imaging Spectroradiometer (MODIS) data, using spectral matching techniques (SMTs), and extensive field knowledge. Map accuracy was evaluated based on independent ground survey data as well as compared with available sub-national level statistics. The producers’ and users’ accuracies of the cropland fallow classes were between 75% and 82%. The overall accuracy and the kappa coefficient estimated for rice classes were 82% and 0.79, respectively. The analysis estimated approximately 22.3?Mha of suitable rice-fallow areas in South Asia, with 88.3% in India, 0.5% in Pakistan, 1.1% in Sri Lanka, 8.7% in Bangladesh, 1.4% in Nepal, and 0.02% in Bhutan. Decision-makers can target these areas for sustainable intensification of short-duration grain legumes.  相似文献   

三维插值方法在2 m温度评估中的应用     

赵滨  李子良  张博 《南京气象学院学报》2016,8(4):343-355

模式地形与实况站点地形高度间固有差异严重影响了2 m温度检验评估精度,传统二维插值方法仅满足预报要素与实况观测间经纬度二维空间上的一致性,而忽略了垂直方向的一致性问题,使得检验评估中预报与观测不在同一三维空间上进行检验,从而引起严重的评估误导.利用模式三维预报变量,结合近地面要素预报产品,建立新的近地面要素三维插值方法,以确保预报与观测在三维空间上保持一致性.利用2013年7月整月24 h预报产品与观测的对比分析发现,新插值方法有效地改进了由于地形误差引起的评估误导问题,在不同地形高度条件下均保持了较为一致的误差分布趋势,显示其评估结论不受地形因素影响,具有更好的实际应用价值.进一步关注新插值方法在复杂地形区不同模拟分辨率条件下的评估改进效果,采用GRAPES区域预报模式（GRAPES-MESO4.0）针对2012年7月个例,对青藏高原复杂地形区进行了不同分辨率（45、15、5和2 km）条件下的60 h模拟敏感分析,结果表明新插值方法在高分辨率条件下（2 km）依然显示出明显的改进优势.  相似文献