On the postprocessing removal of correlated errors in GRACE temporal gravity field solutions

We revisit the empirical moving window filtering method of Swenson and Wahr (Geophys Res Lett 33:L08402, 2006) and its variants, Chambers (Geophys Res Lett 33:L17603, 2006) and Chen et al. (Geophys Res Lett 34: L13302, 2007), for reducing the correlated errors in the Stokes coefficients (SCs) of the spherical harmonic expansion of the GRACE determined monthly geopotential solutions. Based on a comparison of the three published approaches mentioned, we propose a refined approach for choosing parameters of the decorrelation filter. Our approach is based on the error pattern of the SCs in the monthly GRACE geopotential solutions. We keep a portion of the lower degree-order SCs with the smallest errors unchanged, and high-pass filter the rest using a moving window technique, with window width decreasing as the error of the SCs increases. Both the unchanged portion of SCs and the window width conform with the error pattern, and are adjustable with a parameter. Compared to the three published approaches mentioned, our unchanged portion of SCs and window width depend on both degree and order in a more complex way. We have used the trend of mass change to test various parameters toward a preferred choice for a global compromise between the removal of the correlated errors and the minimization of signal distortion.     

Similarity solution of oblique impact of wedge-shaped water column on wedged coastal structures

The initial stage of plunging wave impact obliquely on coastal structures is analysed. The problem is modelled through an oblique collision of an asymmetrical water wedge and an asymmetrical solid wedge. The gravity effect on the flow is ignored based on the assumption that the ratio of the incoming speed of the wave to the acceleration due to gravity is much larger than the time scale of interest. Similarity solution method based on the velocity potential theory is then used. The problem of this similarity flow is solved by a boundary element method through the Cauchy theorem in the complex plan. Results for the wave elevation and pressure distribution are provided, including the forces and moments, effects of different impact angles and the effects of oblique impact are investigated. In particular, negative pressure near the tip of the solid wedge is observed and its implications are discussed.     

Detecting the relationship between summer rainfall anomalies in eastern china and the SSTA in the global domain with a new significance test method

It is suggested that the multiple samples in a correlation map or a set of correlation maps should be examined with sig-nificance tests as per the Bernoulli probability, model. Therefore, both the contemporaneous and lag correlations of summertime pre-cipitation R in any one of the three regions of Northern China (NC), the Changjiang-Huaihe River Valley (CHRV), and Southern China (SC) with the SSTA in the global domain have been tested in the present article, using our significance test method and the method proposed by Livezey and Chen (1983) respectively. Our results demonstrate that the contemporaneous correlations of sum-mer R in CHRV with the SSTA are larger than those in NC. Significant correlations of SSTA with CHRV R are found to be in some warm SST regions in the tropics, whereas those of SSTA with NC R, which are opposite in sign as compared to the SSTA-CHRV R correlations, are found to be in some regions where the mean SSTs are low. In comparison with the patterns of the contemporaneous correlations, the 1 to 12 month lag correlations between NC R and SSTA, and those between CHRV summer R and SSTA show simi-lar patterns, including the magnitudes and signs, and the spatial distributions of the coefficients. However, the summer rainfall in SC is not well correlated with the SSTA, no matter how long the lag interval is. The results derived from the observations have set up a relationship frame connecting the precipitation anomalies in NC, CHRV, and SC with the SSTA in the global domain, which is criti-cally useful for our understanding and predicting the climate variabilities in different parts of China Both NC and CHRV summer R are connected with El Nino events, showing a'--'pattern in an El Nino year and a'+ +'pattern in the subsequent year.     

基于拔桩能力的自升式平台海外作业优选

针对某海外项目中可能遇到的钻井平台压载后入泥深度过大和拔桩困难的问题,开展平台优选计算。首先搜集了预定作业井位周围井位的地质勘查资料,利用二次插值法进行作业井位地质勘察数据计算,据此计算了桩脚入泥深度,并根据作业平台结构参数计算了平台的拔桩阻力。为解决平台极限拔桩能力小于拔桩阻力的问题,设计了可控冲桩阀和冲桩系统以消除或减小桩靴底部的吸附力、桩靴侧部土体剪切力和桩靴上部土重。最后将平台拔桩能力与最终拔桩阻力进行对比,给出平台推荐结果。     

两形态类型织纹螺(Nassarius)的鉴定

在整理广东珠海高栏岛潮下带的螺类样品时,发现两不同形态类型的织纹螺,一类型鉴定为西格织纹螺（Nassarius siquijorensis）,另一类型与前者在内唇和外唇形态上存在明显差异但其他特征基本相同。比较了两类型个体的齿舌形态,并对选取的5个个体的COⅠ基因序列进行了研究。结果表明,两类型个体的齿舌形态基本一致,齿列数53—66排,中央齿上缘小齿8—12枚;COⅠ基因序列存在较大的变异,709bp的DNA片段上共有40个位点变异,其中38个变异位点为密码子第三位碱基,个体间的碱基差异在2—35bp之间;贝壳变异与DNA变异不存在关系,同类型的个体在DNA序列上差异较大,不同类型个体的差异却极小;在基于COⅠ基因序列构建的系统树中两类型的个体明显聚为一支。依据5条COⅠ基因核苷酸序列推导的氨基酸残基序列完全相同。齿舌形态和分子生物学证据都证实两种类型的个体同属于西格织纹螺。     

Impact of the Three Gorges Dam on reproduction of four major Chinese carps species in the middle reaches of the Changjiang River

Silver carp (Hypophthalmichthys molitrix), bighead carp (Aristichthys nobilis), grass carp (Ctenopharyngodon idella), and black carp (Mylopharyngodon piceus) are the four major Chinese carps and are commercially important aquaculture species in China. Reproduction of these carp has declined since the construction of the Three Gorges Dam (TGD) due to an altered water flow and thermal regime in the Changjiang (Yangtze) River. However, details of the changes in reproduction of the four species are not well understood. To assess the impact of the TGD on reproduction of the four carp, we investigated their eggs and larvae at Yidu City, which is 80 km below the TGD, during 2005–2012. We examined diff erences in larval abundance of the four species in the Jianli section (350 km downstream of the TGD) before (1997–2002) and after (2003–2012) construction of the TGD. Based on these observations, the first spawning date of the four species was delayed a mean of about 25 days after the dam was constructed. Mean egg abundance in the Yidu section of the river was 249 million and mean larval abundance was 464 million, which were significant decreases since the 1980s. Moreover, larval abundance in the Jianli section after the dam was constructed was significantly lower than that before construction (ANCOVA, P<0.05). The observed larval abundance accounted for only 24.66% of the predicted value in 2003 when the dam was first inundated. The present spawning grounds between the TGD and Yidu section of the river are very similar to those described in the 1980s, and some spawning grounds exist upstream of the TGD. Large free-flowing stretches upstream of the TGD and the creation of artificially flooded downstream reaches are needed to stimulate spawning and eff ectively conserve these four major Chinese carps species.     

Effects of salinity and nutrients on the growth and chlorophyll fluorescence of Caulerpa lentillifera

Caulerpa lentillifera is a green algae that distributes worldwide and is cultivated for food. We assessed vegetative propagation of C. lentillifera by measuring the specific growth rate(SGR) and chlorophyll fluorescence of the green algae cultured at different salinities and nutrient levels. The results indicated that C. lentillifera can survive in salinities ranging from 20 to 50,and can develop at salinities of 30 to 40. The maximum SGR for C. lentillifera occurred at a salinity of 35. Both chlorophyll content and the ratio of variable to maximum fluorescence( Fv / Fm) were also at a maximum at a salinity of 35. Photosynthesis was inhibited in salinities greater than 45 and less than 25. Both the maximum SGR and maximum chlorophyll content were found in algae treated with a concentration of 0.5 mmol/L of NO3-N and 0.1 mmol/L of PO 4-P. The photosynthetic capacity of photosystem II(PSII) was inhibited in cultures of C. lentillifera at high nutrient levels. This occurred when NO3-N concentrations were greater than 1.0 mmol/L and when PO4- P concentrations were at 0.4 mmol/L. As there is strong need for large-scale cultivation of C. lentillifera,these data contribute important information to ensure optimal results.     

夏季青藏高原东部地区的水汽输送

本文从分析流场、湿度场的特征入手,对青藏高原东部地区的水汽通量、水汽通量散度进行了计算研究。     

分层式金刚石锯片刀头结构的研究

在阐述了锯齿的磨损机理和分析了圆弧状凸齿产生的原因之后,从理论上推算出了分层式刀头的纯合金层的厚度,并结合生产试验得出了切割花岗岩用锯片刀头层数的计算公式。     

贵阳花溪地区早-中三叠世碳酸盐角砾岩楔沉积特征

早-中三叠世贵阳花溪地区位于浅水碳酸盐台地向深水盆地的过渡带,各沉积体系域特征明显,特别是低水位期碳酸盐角砾岩楔发育。野外调查发现研究区共发育4期低水位碳酸盐角砾岩楔,说明该区在早-中三叠世至少经历了4次明显的海平面变化。碳酸盐角砾岩楔的位置迁移反应了台地边缘位置的迁移和海平面相对变化的大小,其中谷立角砾岩舌相对于其他角砾岩楔向台地方向延伸距离最远,代表了台地边缘位置向台地方向迁移的距离最远,张家湾角砾岩楔代表了安尼初期的海平面快速下降。通过角砾岩楔的沉积特征和各岩石地层单元的几何接触关系判断出该区碳酸盐台地前缘演化过程：缓斜坡型台缘→沉积型台缘→礁镶跌积型台缘。