2014年8月伊犁河谷一次持续降水过程分析     

江友飞  李如琦  彭君 《沙漠与绿洲气象(新疆气象)》2016,10(1):81-87

采用常规观测资料、NCEP逐6小时1。×1。再分析资料、FY-2D云图资料,对2014年8月16日至19日伊犁持续降水过程进行天气动力学分析。结果表明：持续降水发生在100hpa南亚高压呈典型的双体型、500hpa伊朗副高-中亚低值系统-贝加尔湖阻滞脊稳定维持的环流背景下,中亚低槽前的偏南气流将阿拉伯海、孟加拉湾的水汽通过接力输送机制输送到伊犁。200hpa强盛的西南急流、低层辐合、高层辐散抽吸的散度场、上升运动区与正涡度区叠加的动力结构利于持续降水的形成。降水明显时段,800 hPa以下受负湿位涡控制,有条件性对称不稳定。强降水时段的云顶亮温TBB最低值在-48℃左右。持续降水导致伊宁市8月降水量（45.8mm）突破1952年以来的同期历史极值。  相似文献   

地铁隧道断面变形分析方法研究   总被引：2，自引：2，他引：0  

刘冠兰  徐亚明  柏文峰 《测绘通报》2016,(2)

针对目前以单点描述隧道断面变形的不足,本文采用B样条曲线拟合隧道断面扫描数据,计算待分析部位两期曲线段的豪斯多夫距离,以各部位曲线段的整体变形信息来反映断面变形。同时根据地铁隧道断面扫描数据的特点,提出了B样条曲线拟合的主点选取方法以及非断面信息的剔除方法。最后以某地铁隧道断面扫描数据为例,通过加入模拟变形信息拟合分析,验证了该方法的有效性。  相似文献   

NUMERICAL SIMULATION STUDY OF HAIL CLOUD—PART Ⅰ:THE NUMERICAL MODEL     

洪延超  樊鹏 《Acta Meteorologica Sinica》1999,(2)

In order to study mechanisms of hailstone formation and hail suppression with seeding and toobtain optimum seeding technique for hail cloud,a 3-D compressive numerical seeding model forhail cloud is developed.The water substance in hail cloud is divided into 8 categories,i.e.,watervapor,cloud droplet,raindrop,ice crystal,snow.graupel,frozen drop and hail,and the detailedmicrophysical processes are described in a spectrum with two variable parameters and morereasonable particle number/size distributions.Then,the model is able to predict concentration andwater content of various particles.Especially.it can calculate the number of hailstones whosecores are graupel or frozen drop and apply to study mechanism of hailstone formation.Additionally,a conservative equation of AgI as seeding or glacigenous agent is found andnucleation by condensation of artificial nucleus,and nucleation by freezing of cloud droplet or raindrop which contact with AgI particle are considered.The dynamic energy flux of hail shooting onground is used to verify seeding effect.Therefore the model is also used to study mechanism of hailsuppression with seeding and the seeding technique,  相似文献   

Climate changes and human activities recorded in the sediments of Lake Estanya (NE Spain) during the Medieval Warm Period and Little Ice Age   总被引：2，自引：0，他引：2  

Mario Morell��n  Blas Valero-Garc��s  Pen��lope Gonz��lez-Samp��riz  Teresa Vegas-Vilarr��bia  Esther Rubio  Maria Rieradevall  Antonio Delgado-Huertas  Pilar Mata  ��scar Romero  Daniel R. Engstrom  Manuel L��pez-Vicente  Ana Navas  Jes��s Soto 《Journal of Paleolimnology》2011,46(3):423-452

A multi-proxy study of short sediment cores recovered in small, karstic Lake Estanya (42°02?? N, 0°32?? E, 670 m.a.s.l.) in the Pre-Pyrenean Ranges (NE Spain) provides a detailed record of the complex environmental, hydrological and anthropogenic interactions occurring in the area since medieval times. The integration of sedimentary facies, elemental and isotopic geochemistry, and biological proxies (diatoms, chironomids and pollen), together with a robust chronological control, provided by AMS radiocarbon dating and ²¹⁰Pb and ¹³⁷Cs radiometric techniques, enabled precise reconstruction of the main phases of environmental change, associated with the Medieval Warm Period (MWP), the Little Ice Age (LIA) and the industrial era. Shallow lake levels and saline conditions with poor development of littoral environments prevailed during medieval times (1150?C1300 AD). Generally higher water levels and more dilute waters occurred during the LIA (1300?C1850 AD), although this period shows a complex internal paleohydrological structure and is contemporaneous with a gradual increase of farming activity. Maximum lake levels and flooding of the current littoral shelf occurred during the nineteenth century, coinciding with the maximum expansion of agriculture in the area and prior to the last cold phase of the LIA. Finally, declining lake levels during the twentieth century, coinciding with a decrease in human pressure, are associated with warmer climate conditions. A strong link with solar irradiance is suggested by the coherence between periods of more positive water balance and phases of reduced solar activity. Changes in winter precipitation and dominance of NAO negative phases would be responsible for wet LIA conditions in western Mediterranean regions. The main environmental stages recorded in Lake Estanya are consistent with Western Mediterranean continental records, and show similarities with both Central and NE Iberian reconstructions, reflecting a strong climatic control of the hydrological and anthropogenic changes during the last 800 years.  相似文献   

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陈俊勇  党亚明  程鹏飞 《大地测量与地球动力学》2007,27(5):1-4

?????????????????(GNSS)???GPS??????????????GLONASS???????GALILEO?????????????;????????μ?????????????????????????????????·??Ч??????????????????????????λ?????仯????????λ??????????????????λ????????;??????GPS???????λ(PPP)???????  相似文献   

查干凹陷早白垩世碎屑岩储层成岩作用及孔隙演化          下载免费PDF全文

国殿斌  李聪  李忠  王亚明  陈刚  张博明  韩立辉  孔海瑞  杜汶哲 《地质科学》2014,49(4):1258-1268

在对大量薄片和岩心观察分析基础上,结合扫描电镜和全岩分析、 X衍射粘土分析、 包裹体测温等手段,对查干凹陷碎屑岩储层的成岩作用和孔隙演化进行了研究。结果表明: 研究区碎屑岩储层主要为低成分成熟度、 低结构成熟度的长石岩屑砂岩,成岩作用呈现“强压实、 强胶结、 弱交代、 弱溶蚀“的“两强两弱”特征;成岩阶段主要处于中成岩A期,局部达中成岩B期至晚成岩期。两期胶结主要发生在苏二早期和乌兰苏海时期,中浅层（<2 500 m）较低孔隙度主要由于强压实和早期致密胶结所致;较高孔隙度是由于原生孔隙保存较好,长石及碳酸盐胶结物的溶蚀作用导致孔隙度增大。深层碎屑岩储层（>2 500 m）较低孔隙度除压实作用外,碳酸盐致密胶结是主因;较高孔隙度则为早期酸性溶蚀叠加晚期碱性溶蚀产生次生孔隙为主。晚期碱性溶蚀发生在油气充注之后,为无效溶孔。  相似文献   

沈阳城区一次暴雨过程的水汽条件分析     

李典  夏传栋  肖光梁  鲁杨  孟鹏  柴晓玲  孙彬 《干旱气象》2014,(5)

利用Micaps实况资料、东北区域中尺度数值模式分析场资料和常规观测资料,对2013年8月16日沈阳城区暴雨的水汽条件进行了分析。结果表明：850 hPa以下城区上空水汽含量占整层的80％以上,地面比湿呈现快速增加后减少的变化,比湿峰值对应的并不是强降水的最强时刻。强降水发生前,城区地面周围的湿度分布不均匀,水汽输送主要以南北向为主。比湿的迅速增加主要是由于降水前风向和风速的快速变化,其中主要是南风分量的贡献。城区上空垂直方向上水汽主要是850 hPa向上输送,850 hPa以下输送强度逐渐减弱。伴随着强降水的开始,水汽的垂直输送转为高度层越低,输送强度越大。强降水发生时,地面U、V方向上水汽通量快速减小。强降水发生后,地面和高空水汽输送均发生了变化。大气可降水量与降水量之间具有一定的对应关系,可降水量的大小主要是取决于水平水汽通量辐合的大小,水汽局地变化对可降水量的贡献较小。水汽通量的辐合、辐散的大小主要取决于水平风场引起的辐合、辐散的大小。  相似文献   

GPS������ջ��뻷�������о�     

孙福余  张鹏  徐亚明  沈智娟 《大地测量与地球动力学》2012,32(4):144-147

???????????????????????????????????????????????????????????????????????????????????????????????????????????÷??????????????????????β??????????????????????????????????????????????????  相似文献   

A statistical approach to disentangle environmental forcings in a lacustrine record: the Lago Chungará case (Chilean Altiplano)     

Santiago Giralt  Ana Moreno  Roberto Bao  Alberto Sáez  Ricardo Prego  Blas L. Valero-Garcés  Juan José Pueyo  Penélope González-Sampériz  Conxita Taberner 《Journal of Paleolimnology》2008,40(1):195-215

A high resolution multiproxy study (magnetic susceptibility, X-ray diffraction, XRF scanner, gray-colour values, Total Organic Carbon, Total Inorganic Carbon, Total Carbon and Total Biogenic Silica) of the sedimentary infill of Lago Chungará (northern Chilean Altiplano) was undertaken to unravel the environmental forcings controlling its evolution using a number of different multivariate statistical techniques. Redundancy analyses enabled us to identify the main provenance of the studied proxies whereas stratigraphically unconstrained cluster analyses allowed us to distinguish the “outsiders” as result of anomalous XRF scanner acquisitions. Principal Component Analysis (PCA) was employed to identify and isolate the main underlying environmental gradients that characterize the sedimentary infill of Lago Chungará. The first eigenvector of the PCA could be interpreted as an indicator of changes in the input of volcaniclastic material, whereas the second one would indicate changes in water availability. The chronological model of this sedimentary sequence was constructed using 17 AMS ¹⁴C and 1 ²³⁸U/²³⁰Th dates in order to characterize the volcaniclastic input and the changes in water availability in the last 12,300 cal years BP. Comparison of the reconstructed volcaniclastic input of Lago Chungará with the dust particle record from the Nevado Sajama ice core suggested that the Parinacota volcano eruptions were the main source of dust during the mid and Late Holocene rather than the dry out lakes as has previously been pointed out. The comparison of the water availability reconstruction of Lago Chungará with three of the most detailed paleoenvironmental records of the region (Paco Cocha, Lake Titicaca and Salar Uyuni) showed an heterogeneous (and sometimes contradictory) temporal and spatial pattern distribution of moisture. Although the four reconstructions showed a good correlation, each lacustrine ecosystem responded differently to the moisture oscillations that affected this region. The variations in the paleoenvironmental records could be attributed to the dating uncertainities, lake size, lake morphology, catchment size and lacustrine ecosystem responses to the abrupt arid events.  相似文献   

PL-RTK:一个基于伪卫星的实时动态定位系统     

李超  黄劲松  徐亚明  张涛  吴明魁  蔡仁澜 《测绘通报》2014,(12):1-4

介绍了一个伪卫星实时动态定位系统PL-RTK。PL-RTK中,伪卫星星座由一组（不小于4）商业GPS L1信号发射器组成,基准站和流动站均采用商业GPS接收机,数据链采用无线局域网（WLAN）,伪卫星星座之间的时频统一通过控制中心进行调控。PL-RTK需要在已知点上进行静态初始化。实验结果表明,PL-RTK平面方向的定位精度优于1.0cm,高程方向的定位精度优于1.1cm。  相似文献