GOCE gradiometer: estimation of biases and scale factors of all six individual accelerometers by precise orbit determination

A method has been implemented and tested for estimating bias and scale factor parameters for all six individual accelerometers that will fly on-board of GOCE and together form the so-called gradiometer. The method is based on inclusion of the individual accelerometer observations in precise orbit determinations, opposed to the baseline method where so-called common-mode accelerometer observations are used. The method was tested using simulated data from a detailed GOCE system simulator. It was found that the observations taken by individual accelerometers need to be corrected for (1) local satellite gravity gradient (SGG), and (2) rotational terms caused by centrifugal and angular accelerations, due to the fact that they are not located in the satellite’s center of mass. For these corrections, use is made of a reference gravity field model. In addition, the rotational terms are derived from on-board star tracker observations. With a perfect a priori gravity field model and with the estimation of not only accelerometer biases but also accelerometer drifts, scale factors can be determined with an accuracy and stability better than 0.01 for two of the three axes of each accelerometer, the exception being the axis pointing along the long axis of the satellite (more or less coinciding with the flight direction) for which the scale factor estimates are unreliable. This axis coincides with the axis of drag-free control, which results in a small variance of the signal to be calibrated and thus an inaccurate determination of its scale factor in the presence of relatively large (colored) accelerometer observation errors. In the presence of gravity field model errors, it was found that still an accuracy and stability of about 0.015 can be obtained for the accelerometer scale factors by simultaneously estimating empirical accelerations.     

顾及风流压差的艏摇偏差校准方法

多波束艏摇偏差校准是多波束校准的主要内容之一。针对目前多波束艏摇偏差参数不同航次校准其结果相差很大的问题,分析得出了风流压差是产生此差值的主要原因。为此在两种计算风流压差基础上,提出了计算艏摇偏差的改进算法,并利用实测数据进行了验证。验证结果表明：改进方法能够有效地计算出多波束的艏摇偏差,提高了多波束艏摇校准精度。     

A Method for Calculation of Low-Frequency Slow Drift Motions Based on NURBS for Floating Bodies

Through a higher-order boundary element method based on NURBS (Non-uniform Rational B-splines), the calculation of second-order low-frequency forces and slow drift motions is conducted for floating bodies. In the floating body′s inner domain, an auxiliary equation is obtained by applying a Green function which satisfies the solid surface condition. Then, the auxiliary equation and the velocity potential equation are combined in the fluid domain to remove the solid angle coefficient and the singularity of th...     

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华北地区一次长生命史超级单体雹暴特征观测

对2020 年6 月25 日河北南部从保定涞源到沧州东光的超级单体雹暴环境条件、雷达观测及风场反演特征进行了分析。结果表明：①本次超级单体雹暴是在水平对流卷上触发起来并经过不断加强形成的。②超级单体雹暴长时间处于中等到强的基本顺时针旋转环境风的垂直风切变环境中、中气旋维持时间超过3 h以及较强冷池作用,是本次超级单体雹暴维持长生命史的可能原因。③对流单体VIL持续7 h基本维持在55～80 kg·m-2区间,与单体移动路径上降雹时段一致,超过4 h持续出现三体散射长钉或旁瓣回波特征,与本次过程中灾情调查和气象站观测到的大冰雹时间段基本一致,对大冰雹有较好指示意义。④超级单体雹暴出现钩状回波（低层）、回波悬垂“穹隆”结构、风暴顶辐散、ZDR柱和KDP柱等特征。“穹隆”顶部为65 dBz以上反射率因子,该处风场以垂直上升为主,水平风分量较弱,呈现出“穴道〖CD*2〗零域”结构,利于大冰雹增长。超级单体垂直速度随高度增大,利于中气旋形成和维持。     

A STUDY ON THE APPLICATION OF FY-2E CLOUD DRIFT WIND HEIGHT REASSIGNMENT IN NUMERICAL FORECAST OF TYPHOON CHANTHU (1003) TRACK

In this paper, we first analyzed cloud drift wind(CDW) data distribution in the vertical direction, and then reassigned the height of every CDW in the research domain in terms of background information, and finally, conducted contrast numerical experiments of assimilating the CDW data before and after reassignment to examine the impacts on the forecast of the track of Typhoon Chanthu(1003) from 00:00(Coordinated Universal Time) 21 July to 00:00 UTC23 July, 2010. The analysis results of the CDW data indicate that the number of CDWs is mainly distributed in the midand upper-troposphere above 500 h Pa, with the maximum number at about 300 h Pa. The height reassigning method mentioned in this work may update the height effectively, and the CDW data are distributed reasonably and no obvious contradiction occurs in the horizontal direction after height reassignment. After assimilating the height-reassigned CDW data, especially the water vapor CDW data, the initial wind field around Typhoon Chanthu(1003) became more reasonable, and then the steering current leading the typhoon to move to the correct location became stronger. As a result, the numerical track predictions are improved.     

柴达木盆地雅丹地貌区风况数据集

为了明确柴达木盆地雅丹地貌发育的风况特征,对盆地中南部鲸背状雅丹区和西北部长垄状雅丹区的风况分别进行了长期的野外实地观测。对实测的风速风向数据按照罗盘16方位分风速段统计分析,计算输沙势,得到柴达木盆地雅丹地貌区风况数据集。该数据集包括两个数据文件：（1）盆地中南部的鲸背状雅丹区风况数据（WinReg_WhaleBackYardang_QB）;（2）盆地西北部的长垄状雅丹区风况数据（WinReg_LongRidgeYardang_QB）。每个数据文件均包含3个工作表,分别为观测周期内的原始风速风向记录,各月份、季节、年度的风频和输沙势。本数据集存储为.xls格式,压缩后的数据量为2.73 MB。本数据集不仅可准确阐释柴达木盆地雅丹地貌发育的风况特征,也为进一步研究雅丹地貌的发育演化模式奠定了基础。本数据集的相关研究成果发表在《中国沙漠》2013年33卷第5期和《Journal of Arid Land》2019年11卷第5期。     

零通量面方法的应用研究

本文分析了零通量面方法的理论基础,总结了多年应用的效果指出研制相应的仪器,改进计算方法,建立零通量面与气象、地下水位等环境要素的关系模式是今后研究的主要方向。     

南海北部第四系深层等深流沉积特征及类型*

以地震资料为基础, 对南海北部第四系深层等深流沉积进行了研究。南海北部水深约1200～3000m范围内发育大型长条状漂积体、限制型漂积体、陆坡席状漂积体及沉积物波。大型长条状漂积体外形为丘状, 水道在靠陆一侧发育。限制型漂积体主要沉积于地形突起之间的地势相对低洼处, 外形多平坦, 水道较为发育。陆坡席状漂积体外形为席状。沉积物波面积较大, 部分与漂积体伴生。深层等深流在自北东向南西沿南海陆架运动过程中, 在中上陆坡由于地形变化相对较大及科氏力作用影响形成螺旋型等深流, 进而产生次生环流, 形成大型长条状漂积体及限制型漂积体。在中下陆坡因地形相对平坦、开阔, 等深流为层状水流, 多形成陆坡席状漂积体。本研究不仅能提高对南海深层等深流沉积的认识, 还能为油气勘探服务。     

论地质科学中全球变化研究的方法

文章借引用与大气和海洋全球变化有关的研究方法论述了与地质科学有关的全球变化问题。为使地质上的全球变化研究有一个理论依据，首先从数学上划分了自然中的对流与结构。银河系中星云旋臂相对星云星座为结构。太阳系中行星绕太阳的线速度随离太阳的距离均匀递减相对行星的自转是一种结构。在地质上，大陆板块好比是一种结构，而山系就是所谓的对流。结构是分层次的，对流是相对确定层次下的结构而言的。我们通过对银河系、太阳系以及地球大气、海洋和固体地球中结构的描述，就会发现在确定的层次下结构可以用线性动力学的方法描写。文章分析了宏观地质结构形成的力源问题，认为圈层角动量交换应力和地转偏向力的共同作用可以从量级上解释大陆的漂移及其漂移的方向性。最后，对地球科学全球变化研究的前景作了初步的探讨