Influence of ENSO Events on Tropical Cyclone Activity over the Western North Pacific

Based on an analysis of 51-year(1965–2015) data, the influence of El Ni?o–Southern Oscillation(ENSO) events on tropical cyclone(TC) activity is examined over the western North Pacific(WNP). The total number of TCs formed in the entire WNP reduces by about 3.4 TCs per year in La Ni?a years, whereas TCs have an equivalent genesis number between El Ni?o years and climatology. During El Ni?o years, the frequency of TC formation increases remarkably in the southeast quadrant(140?E–180?, 0?–17?N) and decreases in the northwest quadrant(120?–140?E, 17?–30?N). During La Ni?a years, TCs tend to form in the northwest and southwest quadrants(120?–140?E, 0?–17?N) quadrants. TCs tend to become long-lived in the peak season(from July to September) of El Ni?o years and during strong El Ni?o events. TC genesis shows a southeastward positive shift in terms of lifetime and intensity during El Ni?o years, thus more super TCs(winds ≥ 58.64 m s-1) are formed in the southeast quadrant. Further analysis using the genesis potential index(GPI) indicates that the interannual variations in the TC genesis and track are significantly influenced by a combination of large-scale dynamic and thermodynamic conditions.     

Improving Airgun Signal Detection with Small-Aperture Seismic Array in Yunnan

Repeating airgun sources are eco-friendly sources for monitoring the changes in the physical properties of subsurface mediums, but their signals decay quickly and are buried in the noises soon after traveling short distances. Stacking waveforms from different airgun shots recorded by a single seismic station (shot stacking) is the most popular technique to detect weak signals from noisy backgrounds, and has been widely used to process the data of Fixed Airgun Signal Transmission Stations (FASTS) in China. However, shot stacking sacrifices the time resolution in monitoring to recover a qualified airgun signal by stacking many shots at distance stations, and also suffers from persistent local noises. In this paper, we carried out several small-aperture seismic array experiments around the Binchuan FAST Station (BCFASTS) in Yunnan Province,China, and applied the array technique to improve airgun signal detection. The results show that seismic array processing combining with shot stacking can suppress seismic noises more efficiently, and provide better signal-to-noise ratio (SNR) and coherent airgun signals with less airgun shots. This work suggests that the array technique is a feasible and promising tool in FAST to increase the time resolution and reduce noise interference on routine monitoring.     

基于新型观测算子的双偏振雷达雨滴谱变分反演

提出一种基于变分理论的双偏振多普勒天气雷达反演雨滴谱方法,最优反演雨滴谱的同时可实现衰减订正。反演过程中使用一种新型观测算子,利用滴谱仪实测数据计算状态变量和双偏振参量,使观测算子更能代表本地降水特性。将新型观测算子、误差协方差矩阵和状态变量的先验估计用于代价函数中,基于高斯-牛顿迭代方法求解代价函数得到最优雨滴谱。利用理想模拟试验和南京信息工程大学C波段双偏振多普勒天气雷达实测个例对算法进行验证和评估。结果表明：算法反演得到的状态变量(液态水含量LWC和质量权重平均直径D_m)与滴谱仪数据计算结果的相关系数达到了0.96和0.80,相对偏差为25.19%和10.63%,均方根误差比常规反演结果改善了50%左右,比基于模拟观测算子的变分反演结果改善了30%左右,最优反演雨滴谱得到的降雨率R和雨量计数据相关系数达到0.89,相对偏差为14.78%。     

中国南海天然气水合物第二次试采主要进展

泥质粉砂型天然气水合物被认为是储量最大开采难度亦最大的水合物储层,2017年南海天然气水合物试采,初步验证了此类水合物储层具备可开采性。在总结前次试采认识的基础上,对试采矿体进行优选、精细评价、数值与试验模拟和陆地试验,中国地质调查局于2019年10月—2020年4月在南海水深1225 m神狐海域进行了第二次天然气水合物试采。本次试采攻克了钻井井口稳定性、水平井定向钻进、储层增产改造与防砂、精准降压等一系列深水浅软地层水平井技术难题,实现连续产气30 d,总产气量86.14×104m3,日均产气2.87×104m3,是首次试采日产气量的5.57倍,大大提高了日产气量和产气总量。试采监测结果表明,整个试采过程海底、海水及大气甲烷含量无异常。本次成功试采进一步表明,泥质粉砂储层天然气水合物具备可安全高效开采的可行性。     

Characteristics and Natural Gas Origin of Middle−Late Triassic Marine Source Rocks of the Western Sichuan Depression, SW China

A scientific exploration well(CK1) was drilled to expand the oil/gas production in the western Sichuan depression, SW, China. Seventy-three core samples and four natural gas samples from the Middle–Late Triassic strata were analyzed to determine the paleo-depositional setting and the abundance of organic matter(OM) and to evaluate the hydrocarbon-generation process and potential. This information was then used to identify the origin of the natural gas. The OM is characterized by medium n-alkanes(n C_(15)–n C_(19)), low pristane/phytane and terrigenous aquatic ratios(TAR), a carbon preference index(CPI) of ～1, regular steranes with C_(29) C_(27) C_(28), gammacerane/C_(30) hopane ratios of 0.15–0.32, and δD_(org) of-132‰ to-58‰, suggesting a marine algal/phytoplankton source with terrestrial input deposited in a reducing–transitional saline/marine sedimentary environment. Based on the TOC, HI index, and chloroform bitumen "A" the algalrich dolomites of the Leikoupo Formation are fair–good source rocks; the grey limestones of the Maantang Formation are fair source rocks; and the shales of the Xiaotangzi Formation are moderately good source rocks. In addition, maceral and carbon isotopes indicate that the kerogen of the Leikoupo and Maantang formations is type Ⅱ and that of the Xiaotangzi Formation is type Ⅱ–Ⅲ. The maturity parameters and the hopane and sterane isomerization suggest that the OM was advanced mature and produced wet–dry gases. One-dimensional modeling of the thermal-burial history suggests that hydrocarbon-generation occurred at 220–60 Ma. The gas components and C–H–He–Ar–Ne isotopes indicate that the oilassociated gases were generated in the Leikoupo and Maantang formations, and then, they mixed with gases from the Xiaotangzi Formation, which were probably contributed by the underlying Permian marine source rocks. Therefore, the deeply-buried Middle–Late Triassic marine source rocks in the western Sichuan depression and in similar basins have a great significant hydrocarbon potential.     

青海省同仁地区上二叠统石关组上部火山岩的新发现及其地球化学特征和构造环境意义

青海省同仁地区位于秦、祁结合部,构造演化历史悠久.在该区隆务河两侧广泛发育着二叠、三叠纪地层,通过两套地层岩石组合分析,我们认为晚二叠世晚期至早三叠世早期该区属于半深海浊积扇相沉积环境.在该区晚二叠世晚期地层中新发现一套火山岩,火山岩的岩石组合主要为玄武岩、安山岩、玄武安山岩等.根据岩石的常量元素特征,可以将本区火山岩分为两部分:下部岩石的SiO2含量为49.04%~52.43%,平均为51.28%,TiO2含量为0.67%~1.11%,平均为0.9%,ALK值为2.64%~3.6%.通过常量元素投点图分析,本组火山岩岩性偏基性,属于拉斑玄武岩系列,显示高钛玄武岩特征.上部岩石的SiO2含量为56.25%~60.36%,平均为58.76%,TiO2含量为0.52%~0.63%,平均为0.58%,ALK值在5.26%~5.54%之间.岩性偏中性,属于钙碱性系列,显示低钛玄武岩特征.火山岩的稀土元素也有明显差异,下部稀土总量较低,∑REE=(61.7~97.17)×10-6,(La/Lu)N比值平均为3.07,轻重稀土分馏不明显,显示与过渡型洋中脊玄武岩相似的特征;而上部稀土总量较高,∑REE=(107.51~143.32)×10-6,(La/Lu)N比值平均为7.78,轻重稀土分馏明显,稀土分配曲线显示与岛弧安山岩相似的特征.该区火山岩的微量元素比值蛛网图显示与岛弧钙碱性玄武岩-过渡类型玄武岩具有较强的相似性.构造环境判别显示出本区火山岩具有从拉张的过渡型洋中脊环境到闭合的岛弧环境的演化特征.     

香港CORS站坐标时间序列分析研究

针对不同地区连续运行参考站(CORS)坐标时间序列周期特性与噪声特性存在的差异性问题,本文采用功率谱分析法和极大似然法分析香港卫星参考站网(SatRef)的坐标时间序列.研究结果表明,参考站点的三个坐标分量上都存在明显的年周期项与半年周期项.各参考站坐标分量上的噪声特性存在多样化的特征,白噪声(WN)加闪烁噪声(FN)是主要噪声模型,仅考虑WN而忽视有色噪声(CN)的做法会大大低估参数估计的不确定度.根据最优噪声模型估值得出的SatRef站速度场在水平方向上有整体向东南方向运动的趋势,与华南块体的运动结果基本一致.     

基于遥感和GIS的舟山岛岸线资源时空变迁及其利用演进研究

本文以舟山岛为例,以乡镇街道为基本分析单元,根据遥感与GIS方法,进行了1999-2012年间海岸线长度与人工岸线比例、曲折度、利用集约度、资源利用类型的时空变化观测与统计分析。结果表明:(1)舟山岛的岸线在1999年至2012年间不断变化,但变化幅度逐渐减缓,逐渐趋于稳定。区域集中性明显,主要集中在生态风险低的区域。在岸线范围变化的同时,人工化指数也在不断上升;(2)本岛岸线利用方式变化明显,主导利用方式为港口与工业岸线和城镇生活岸线。岸线各利用类型存在部分相互转化,主要是对其它用途岸线开发。舟山岛岸线利用用途相互转化较为合理;(3)随着岸线范围与利用类型的变化,舟山岛岸线利用集约度不断提高,说明本岛对于岸线利用的定位逐渐精准化。结合舟山市海洋功能区划岸线管理效果的回顾性分析,对舟山岛乃至更多海岛县的岸线资源未来的可持续发展提出合理意见。     

我国海洋渔业研究的热点与前沿趋势 ——基于CiteSpace5.1的文献计量分析

文章以1992—2018年CNKI总库中文核心期刊与CSSCI中文社会科学引文数据库中海洋渔业研究的文献记录为对象,借助CiteSpace文献计量软件绘制出海洋渔业研究的作者、机构、关键词等相关图谱并得出如下结论:发文量整体呈波动状态,2007年以后,海洋渔业研究的发文量迅速增长;作者及机构之间学术交流合作少,空间分布相对分散,尚未形成一批高产高影响力的作者群;研究热点主要为可持续发展、海洋渔业资源、海洋产业等;今后海洋牧场、蓝色粮仓、转型升级、凡纳滨对虾等将成为未来的研究前沿。     

Twenty years of ocean observations with China Argo

The international Argo program, a global observational array of nearly 4 000 autonomous profiling floats initiated in the late 1990s, which measures the water temperature and salinity of the upper 2 000 m of the global ocean, has revolutionized oceanography. It has been recognized one of the most successful ocean observation systems in the world. Today, the proposed decade action “OneArgo” for building an integrated global, full-depth, and multidisciplinary ocean observing array for beyond 2020 ...