Sample Optimization of Ensemble Forecast to Simulate a Tropical Cyclone Using the Observed Track

Ensemble forecasting is widely used in numerical weather prediction. However, the ensemble may not satisfy a perfect Gaussian probability distribution because of a limited number of members, with some members significantly deviating from the true atmospheric state. Such outliers (belonging to low probability events) may downgrade the accuracy of an ensemble forecast. In this study, the observed track of a tropical cyclone (TC) is used to restrict the probability distribution of samples by investigating the evolution of TCs. Unlike data assimilation, the method we employed uses observational data. By restricting the probability distribution, ensemble spread could be decreased through sample optimization. In addition, the prediction results showed that track and intensity errors could be reduced by sample optimization. When the vertical structures of TCs considered in this study were compared, different thermal structures were found. This difference may have been caused by sample optimization, which may affect intensity and track. Nevertheless, it should be noted that the replacement of a large number of inferior samples may inhibit the improvement of simulated results.     

圆锥扫描式机载激光测深系统扫描轨迹建模与分析

对圆锥扫描式机载激光测深系统在海面上的激光脚点扫描轨迹进行几何建模,重点分析了水文模式下激光脚点扫描轨迹的平均测点密度和覆盖效率。根据设定的几何模型,以CZMIL机载激光测深系统为例,计算得到单航线测量模式下双向扫描区域激光脚点"最小距离"小于1.6 m的比例为99.78%,5 m×5m大小的格网内激光脚点的平均数目为11.93个。另外,对激光测深系统旁向重叠度和两条航线扫描轨迹进行了分析,认为31.3%的旁向重叠度可以保证不产生飞行漏洞,但对激光脚点的测点密度提升效果并不明显。最后,对激光脚点分布的不均匀性进行了分析,讨论了不同的激光测深系统参数对测点密度和测量效率的影响效果。     

Sensitivity of the simulation of tropical cyclone size to microphysics schemes

The sensitivity of the simulation of tropical cyclone(TC) size to microphysics schemes is studied using the Advanced Hurricane Weather Research and Forecasting Model(WRF). Six TCs during the 2013 western North Pacific typhoon season and three mainstream microphysics schemes–Ferrier(FER), WRF Single-Moment 5-class(WSM5) and WRF Single-Moment6-class(WSM6)–are investigated. The results consistently show that the simulated TC track is not sensitive to the choice of microphysics scheme in the early simulation, especially in the open ocean. However, the sensitivity is much greater for TC intensity and inner-core size. The TC intensity and size simulated using the WSM5 and WSM6 schemes are respectively higher and larger than those using the FER scheme in general, which likely results from more diabatic heating being generated outside the eyewall in rainbands. More diabatic heating in rainbands gives higher inflow in the lower troposphere and higher outflow in the upper troposphere, with higher upward motion outside the eyewall. The lower-tropospheric inflow would transport absolute angular momentum inward to spin up tangential wind predominantly near the eyewall, leading to the increment in TC intensity and size(the inner-core size, especially). In addition, the inclusion of graupel microphysics processes(as in WSM6) may not have a significant impact on the simulation of TC track, intensity and size.     

T639台风预报误差与环境场变量的相关分析和回归分析

利用国家气象中心全球谱模式T639L60(简称T639)数值预报结果和上海台风研究所整编的台风最佳路径数据,基于2009—2010年的样本,分析了西北太平洋和南海台风的环境场预报变量与路径预报误差的相关性,利用线性回归分析,建立了T639台风中心预报误差与环境风整层垂直切变、400 hPa台风环流强度的24~120 h各预报时效线性预估模型(建模样本数分别为299、232、170、117和84个),并利用2011年的样本对模型进行了检验(检验样本数分别为182、146、117、85和61个)。初步结果表明,环境风垂直切变与路径误差呈正相关,台风各层环流强度与路径误差大致呈负相关,其中400 hPa上的负相关性最明显;由环境风垂直切变与400 hPa台风环流强度建立的线性预估模型能对路径预报误差作出定性估计,其中24h预报时效的预估模型有较好的预估效果。     

室内用户语义位置模式挖掘研究——以商场为例

结合室内轨迹数据的特点,研究了室内移动对象语义轨迹序列处理方法,以及利用LDA主题模型与用户历史轨迹进行室内商场用户分类的方法。提出了通过关联规则分析挖掘用户语义位置模式的方法,并以北京某大型商场的实际用户轨迹数据为例,对所提出的方法进行了实验验证。     

鄂尔多斯盆地东北部差异隆升过程裂变径迹分析

基于磷灰石裂变径迹(AFT)的分析方法,探讨鄂尔多斯盆地东北缘差异隆升过程及其隆升强度,为鄂尔多斯盆地东北缘(晋西挠摺带府谷—吴堡区段)构造演化历史及其与多种能源矿产耦合关系提供新的认识。不同构造单元及其不同层系样品的AFT分析表明:研究区北段府谷—兴县地区构造抬升相对较早,且经历了白垩纪晚期(86~56Ma)和古近纪(44~37 Ma)两次隆升过程,平均隆升速率分别为24.5 m/Ma和41.8 m/Ma;研究区中段紫金山地区抬升相对较晚,主控构造事件发生在晚白垩世末期—古近纪早期(68~56 Ma)和古近纪中晚期(35 Ma),平均隆升速率分别为48.8 m/Ma和49.2 m/Ma;研究区南段临县—吴堡地区抬升最晚(35~21 Ma),平均隆升速率为73.9 m/Ma。因此,鄂尔多斯盆地东北缘晚白垩世以来的差异隆升过程具有北段抬升早、中段抬升相对较晚和南段抬升更晚的特点,南北区段统一的强烈构造抬升活动主要发生在古近纪以来的晚近时期,且构造隆升强度由南向北逐渐减弱。结合已有的成矿(藏)年代学资料分析表明,鄂尔多斯盆地东北缘关键构造事件及其隆升强度与多种矿产耦合成矿(藏)事件关系密切,构造事件与成藏(矿)事件呈现出显著的协同耦合特点。     

延页平3井大偏移距水平井减阻降摩技术研究

减阻降摩技术是大偏移距水平井成功完钻的关键技术之一。通过对井眼轨迹参数优化,优选出具有低摩阻系数的井眼轨迹;建立摩阻/扭矩分析模型,分析了钻井液粘滞力和管柱屈曲对摩阻的影响,推导出摩阻/扭矩计算公式,提出了摩阻/扭矩预测的方法;采用低摩阻系数的油基钻井液,将摩阻系数降低了65.2%;采用漂浮下套管技术,极大地降低了下套管过程中的摩阻。延页平3井中成功应用上述技术,准确地预测了钻井过程的摩阻,解决了大偏移距水平井钻井过程中的托压问题,实现了套管一次性下放到位。延页平3井的应用表明：上述技术可以在大偏移距水平井中推广使用,并对国内其他地区大偏移距水平井施工有一定借鉴意义。     

Aspects of the structural and late thermal evolution of the Redbank Thrust system,central Australia: Constraints from the Speares Metamorphics

We present new data on the field geology and late thermal evolution of the Redbank Thrust system in the Arunta Block of central Australia. Geochronological and field data from the Speares Metamorphics are also used to relate the thermal evolution of the Redbank Thrust system to the structural evolution of the region. We show that several stages in the evolution might be discerned. An originally sedimentary sequence was intruded by mafic intrusions and then deformed during partial melting to form the principal foliation observed in the region (D1). This sequence was then folded during D2 into upright folds with north‐ to northeast‐plunging fold axes. These events are likely to correlate with the Strangways and/or Argilke and Chewings Orogenies known from previous studies. Subsequently, the Redbank Thrust was initiated during D3. This event is recognised by deflection of the host rocks into the shear zone and might therefore have been associated with a component of strike‐slip motion. It occurred probably at or before 1500–1400 Ma. Subsequent north‐over‐south thrust motion in the Redbank Thrust formed the intense mylonitic fabric and folded the mylonitic fabric during D4 into asymmetric folds with shallow fold axes. New ⁴⁰Ar/³⁹Ar K‐feldspar ages from three samples collected from variably deformed branches of the Redbank Thrust and undeformed rocks in the Speares Metamorphics suggest that most parts of the Redbank Thrust system cooled relatively slowly after metamorphism and deformation in the Mesoproterozoic so that the D4 thrusting might have been very long‐lived. Minimum ages of the K‐feldspar age spectra show that the entire region cooled below 200°C by approximately 300 Ma. Apatite fission track ages from nine samples show that cooling through the apatite partial annealing zone occurred during Cretaceous time (ca 150–70 Ma) and modelled cooling histories are consistent with the cooling rates obtained from the K‐feldspar data. They indicate that final exhumation of the Redbank Thrust system occurred probably in response to erosion, possibly driven by rifting around the margins of Australia.     

A generalized model for geosynthetic reinforced railway tracks resting on soft clays

The present study pertains to the development of a foundation model for predicting the behavior of geosynthetic reinforcement railway track system rested on soft clay subgrade. The ballast and sub‐ballast layers have been idealized by Pasternak shear layer. The geosynthetic layer is represented by a stretched rough elastic membrane. Burger model has been used to characterize the soft clay subgrade. Numerical solutions have been obtained by adopting the finite difference scheme combined with non‐dimensioning the governing equations of the proposed model. The results confirm that the present model is quite capable of predicting the time‐dependent settlement response of geosynthetic reinforcement railway track system placed on soft clay subgrade. The surface settlement profile and mobilized tensile load of geosynthetics has been evaluated by considering variation in the wheel load, sleeper width, thickness of ballast and sub‐ballast layers and shear modulus of ballast and sub‐ballast layers. It has been observed that an increase in the sleeper width by 24% results in the reduction in central settlement and mobilized tensile load by 6.5% and 20.1%, respectively. It was found that with a 50% increase in the thickness of the ballast layer, the central settlement has decreased by 7.3% and the mobilized tension at the zone of maximum curvature has increased by 24.6%. However, with an increase in the thickness of the sub‐ballast layer, a considerable reduction in both central settlement and the mobilization of tension on geosynthetic has been noticed. The pattern of variation of settlement and mobilized tension for an increase in the shear modulus of ballast and sub‐ballast material was found to be almost similar. Copyright © 2014 John Wiley & Sons, Ltd.     

A SIMULATION STUDY OF THE INFLUENCE OF LAND FRICTION ON LANDFALL TROPICAL CYCLONE TRACK AND INTENSITY

A quasi-geostrophic barotropic vorticity equation model is used to simulate the influences of topographic forcing and land friction on landfall tropical cyclone track and intensity. The simulation results show that tropical cyclone track may have sudden deflection when the action of topographic friction dissipation is considered, and sudden deflection of the track is easy to happen and sudden change of tropical cyclone intensity is not clear when the intensity of tropical cyclone is weak and the land friction is strong.The land friction may be an important factor that causes sudden deflection of tropical cyclone track around landfall.