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台风初始化方案最大的困难在于其只能根据有限的观测资料(台风中心位置、最低气压、最大风速和大风半径等)来构造一个与模式动力-物理过程协调的涡旋模型。首先根据实际观测资料对背景场中的涡旋扰动进行重定位和风速调整,然后将分析增量更新(Incremental Analysis Update,IAU)技术应用于台风初始化方案中,将调整后的涡旋当作一个强迫项逐渐加入到模式预报过程中,通过模式自身调整来得到一个协调性较好的台风初始结构,从而改善模式对台风的预报性能。对“山竹”台风的多次预报结果表明:(1)台风初始化对于台风路径误差影响较小,对于强度预报改进则比较明显。特别是在台风生成初期,台风初始化技术能够有效地增强全球模式分析场中的涡旋强度,并解决预报过程中强度较弱的问题。(2)根据预先给定的三维风场,IAU技术能通过模式自身预报过程对其他变量进行调整,从而得到一个热力和动力协调的初始涡旋结构。相对于仅对初始风场的调整,它对24 h之后的路径和强度预报误差会有更进一步的改善。(3)对IAU中的松弛时间进行参数敏感性试验,发现该变量取3—6 h效果较好。   相似文献   
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研究了IAU2000对GPS卫星轨道确定的影响。以2006年DOY186的GPS数据为例,分析了GPS卫星在IAU2000决议模型以及原有模型下,惯性参考系统以及地固坐标系中轨道的差别。结果显示,采用不同模型,卫星轨道在惯性参考系中的差值存在周期性,其中X、Z方向的幅度达到了2.5 m,Y方向的幅度约为1 m;在地固系中,轨道差别也存在周期,幅度约为4 mm。并对卫星轨道的差值进行了统计,得出了在惯性系下,不同模型引起轨道差值的3D RMS为m级。  相似文献   
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In 1970 the IAU defined any object'snorth pole to be that axis of rotation which lies north of the solar system's invariable plane. A competing definition in widespread use at some institutions followed the right hand rule whereby the north axis of rotation was generally said to be that that of the rotational angular momentum. In the case of the latter definition, the planet Neptune and its satellite Triton would have their north poles in opposite hemispheres because Triton's angular momentum vector is in the hemisphere opposite from that of Neptune's rotation angular momentum.The IAU resolutions have been somewhat controversial in some quarters ever since their adoption. A Working Group has periodically updated the recommended values of planet and satellite poles and rotation rates in accordance with the IAU definition of north and the IAU definition of prime meridian. Neither system is completely satisfactory in the perception of all scientists, and some confusion has been generated by publishing data in the two different systems.In this paper we review the IAU definitions ofnorth and of the location ofprime meridian and we present the algorithm which has been employed in determining the rotational parameters of the natural satellites. The IAU definition of the prime meridian contains some ambiguities which in practice have been specified by the numerical values published by the IAU working group but which have not yet been explicitly documented. The purpose of this paper is to explicitly document the algorithm employed by the IAU working group in specifying satellite poles and rotation rates.  相似文献   
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