Continental drift,plateau uplift,and the evolutions of monsoon and arid regions in Asia,Africa, and Australia during the Cenozoic

Monsoon and arid regions in the Asia-Africa-Australia(A-A-A) realm occupy more than 60% of the total area of these continents. Geological evidence showed that significant changes occurred to the A-A-A environments of the monsoon and arid regions, the land-ocean configuration in the Eastern Hemisphere, and the topography of the Tibetan Plateau(TP) in the Cenozoic. Motivated by this background, numerical experiments for 5 typical geological periods during the Cenozoic were conducted using a coupled ocean-atmosphere general circulation model to systemically explore the formations and evolutionary histories of the Cenozoic A-A-A monsoon and arid regions under the influences of continental drift and plateau uplift. Results of the numerical experiments indicate that the timings and causes of the formations of monsoon and arid regions in the A-A-A realm were very different. The northern and southern African monsoons existed during the mid-Paleocene, while the South Asian monsoon appeared in the Eocene after the Indian Subcontinent moved into the tropical Northern Hemisphere. In contrast, the East Asian monsoon and northern Australian monsoon were established much later in the Miocene. The establishment of the tropical monsoons in northern and southern Africa, South Asia, and Australia were determined by both the continental drift and seasonal migration of the Inter-Tropical Convergence Zone(ITCZ), while the position and height of the TP were the key factor for the establishment of the East Asian monsoon. The presence of the subtropical arid regions in northern and southern Africa,Asia, and Australia depended on the positions of the continents and the control of the planetary scale subtropical high pressure zones, while the arid regions in the Arabian Peninsula and West Asia were closely related to the retreat of the Paratethys Sea. The formation of the mid-latitude arid region in the Asian interior, on the other hand, was the consequence of the uplift of the TP.These results from this study provide insight to the important roles played by the earth's tectonic boundary conditions in the formations and evolutions of regional climates during geological times.     

柴达木盆地一里坪盐湖卤水水化学及夏季蒸发中钾、锂、硼行为

本文综合利用Na⁺,K⁺,Mg²⁺//Cl^-,SO₄^2--H₂O五元体系干基图、水图、钠图,研究柴达木盆地一里坪盐湖硫酸盐型卤水水化学特征受外来淡水补给掺杂、选择性溶解、年温差等多因素影响产生的季节性变化,其中温度为主要因素.当卤水温度降低至0℃,开始析出芒硝,水化学变质系数MgSO₄/MgCl₂比值急剧下降,水化学特征由硫酸镁亚型向氯化物型转化过渡.通过20~25℃晶间卤水L10和L20蒸发实验研究,确定了一里坪卤水蒸发路线、液固相组成、物相鉴定、水化学特征系数、离子行为等变化及成盐特征,并与25℃ Na⁺,K⁺,Mg²⁺//Cl^-,SO₄^2--H₂O五元体系介稳相图理论预测计算综合对比,二者吻合性比较好,整体相对误差能控制在5%范围内,利用相图理论计算能够很好地指导实际硫酸盐型卤水蒸发析盐.利用水化学特征系数KCl/MgCl₂、MgSO₄/MgCl₂,研究了25℃硫酸盐型盐湖卤水钾盐成盐特征,当变质系数MgSO₄/MgCl₂高于0.13时,卤水钾盐矿物析出的同时,伴随有泻利盐共同析出.利用含Li⁺、borate、Mg²⁺水盐体系相图,研究一里坪老卤水深度蒸发中Li、B的行为,理论预测计算结果,剩余老卤水Mg²⁺/Li⁺比值降至27时,卤水中的Li、B始终以离子形式赋存于卤水中继续富集,此时卤水的累积成卤率仅为2.50%~3.20%,须引入新的工艺技术进行Li、B提取.研究结果为极高镁锂比、高镁硼比的硫酸盐型卤水的综合开发利用提供了理论支持.     

青岛原点与坎门零点(二)

回顾了我国大地测量高程基准点的历史变革过程,着重讨论坎门基准点。介绍了青岛水准原点与坎门零点的联测过程,以及坎门零点的利用情况。     

The Rockall Bank Mass Flow: Collapse of a moated contourite drift onlapping the eastern flank of Rockall Bank,west of Ireland

The Rockall Bank Mass Flow (RBMF) is a large, multi-phase submarine slope failure and mass flow complex. It is located in an area where the Feni Drift impinges upon the eastern flank of the Rockall Bank in the NE Atlantic. A 6100 km² region of slope failure scarps, extending over a wide water depth range and with individual scarps reaching up to 22 km long and 150 m high, lies upslope of a series of mass flow lobes that cover at least 18,000 km² of the base of slope and floor of the Rockall Trough. The downslope lobe complex has a negative topographic relief along much of its northern boundary, being inset below the level of the undisplaced contourite drift at the base of slope. The southern margin is topographically more subtle but is marked by the sharp termination of sediment waves outside the lobe. Within the lobe complex the southern margin of the largest lobe shows a positive relief along its southern margin. The initial failure is suggested to have occurred along coherent layer-parallel detachment surfaces at depths of up to 100 m and this promoted initial downslope block sliding which in turn transformed into debris flows which moved out into the basin. The remains of a deep erosional moat linked to the onlapping contourite complex bisects the region of failed slope, and post-failure thermohaline currents have continued to modify the mass flow in this area. Differential sedimentation and erosion associated with the moat may have promoted slope instability. Following the major failure phase, continuous readjustments of the slope occurred and resulted in small-volume turbidites found in shallow gravity cores collected on the lobes. The short term trigger for the failure remains uncertain but earthquake events associated with a deep-seated tectonic lineament to the north of the mass flow may have been important. A Late Pleistocene age for the slope failure is likely. The RBMF is unusual in that it records large-scale collapse of a contourite body that impinged on a sediment-undersupplied slope system. Unlike many other large slope failure complexes along the NE Atlantic margin, the RBMF occurs in a region where there was little overloading by glacial sediment.     

GPS残差信号提取的时间序列分析方法

作者使用零基线单差模型研究并讨论了GPS量测噪声的时相关特性,并得出了GPS观测噪声具有类似白噪声或一阶高斯马尔科夫噪声的特殊性质。利用观测噪声所具备的这种特殊性质,作者首先尝试了从时间域的角度分离和提取了残差序列中的多路径信号特性,成功验证了多路径信号在连续两个恒星日内会有所重复的结论。作者提出了一种使用时相关分析法检测观测序列中周期信号(如冰期反弹、固体潮、极潮等)的设想并就其可行性进行了分析研究。最后,针对观测噪声的这种特殊性质,探讨了结合使用小波分析法提取GPS沉降监测信号的可行性。     

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。     

Temporal variation in abundance and fecundity of the invading copepod Eurytemora americana in Bahía Blanca Estuary during an unusual year

Eurytemora americana has been only reported as invader in Bahía Blanca Estuary, Argentina within the South Hemisphere. There are a few experimental researches under laboratory conditions done with this species and its reproductive behaviour around the world is very scarce. Consequently, it is still not possible to completely understand its population dynamics. In the present study, E. americana reproductive temporal behaviour and relationships among abundance, female size, egg production and hatching success were examined in the Bahía Blanca Estuary, during 2007 pulse. In order to determine the potential relationships between these variables and the environmental variables, experimental incubations were conducted in the laboratory simulating natural conditions. Spearman’s rank correlation was used to analyze the relationships among all variables. Temporal change of biotic and environmental variables was corroborated by a Mann–Whitney/Kruskal–Wallis non-parametric tests, with significant differences (p ? 0.01) in all variables throughout the study. Abundance population results showed very high values in relation to those recorded in recent years in Bahía Blanca Estuary. This response could be due to the unusual combination of environmental factors (polar wave with temperatures ≤6 °C and a drought period with high salinities, 32.7–36.6) recorded during the studied winter period. Significant positive correlations between abundance and salinity (p < 0.01, n = 226), and hatching success (p < 0.01, n = 25) as well as a significant negative correlation between abundance and chlorophyll a (p < 0.01, n = 226) were found. Although E. americana shows a k-strategy within its annual pulse, it presented two markedly distinct behaviours depending on temporal environmental variability. From July to early september, when the estuary evidenced high salinity, low temperature and high food availability, E. Americana showed large females, large clutch size and high hatching success. When environmental conditions became unfavorable from September to October, small females, small clutch size and very low hatching success were observed. The latter is associated with diapause egg laying which ensures population recruitment. According to our findings the particular combination of low temperatures, high salinities and high available food (i.e. variables which each year modulate its pulse) during 2007 winter–spring, favored the great development of E. americana. This invading species in its opportunistic role has managed to exploit a vacant niche in the estuary, developing two different behaviours within the k-strategy depending on change in environmental conditions.     

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...     

The simulation of the geometry of a tuna purse seine under current and drift of purse seiner

It was necessary to obtain a more practical interactive precise model of the three-dimensional (3-D) geometry during purse seine operations considering movements of fishing vessel and details of the sea condition. The changes in the shape of a purse seine from shooting to pursing during pelagic skipjack fishing was recorded in the Southwest Pacific Ocean by photographs of the scanning sonar with in situ measurements of water flow by a current meter. The modeling of 3-D geometry during purse seining was established using finite element methods, as resultant force vector from flow drag, buoyancy, sinking force, tension of pulling or pursing acting on net panels in connection with drift of fishing vessel with time elapsed from the start of shooting to the end of pursing. The simulation results were matched closely by field measurements as a heart-like shape in upper net near floatline and a water-drop shape in purse line following drift of ship towards inside net circle during pursing. This model of a purse seine can be extended to almost any kind of purse seine generating real fishing parameters and to modeling fish capture process.