Detecting temporal trends and environmentally-driven changes in the spatial distribution of bottom fishes and crabs on the eastern Bering Sea shelf

This study uses a 30-year time series of standardized bottom trawl survey data (1982–2011) from the eastern Bering Sea shelf to model patterns of summer spatial distribution for various bottom fishes and crabs in response to changes in the areal extent of the cold pool, time lag between surveys, and fluctuations in population abundance. This investigation is the first to include data for the 2006–2010 cold period and to use between-year comparisons of local and shelf-wide spatial indices to test specific responses to three different isothermal boundaries within the cold pool. Distributional shifts in population varied considerably among species and directional vectors for some species were greater in magnitude to the east or west than to the north or south; however, in general, eastern Bering Sea shelf populations shifted southward in response to the increasing cold pool size, and after accounting for differences in temperature and population abundance, there was still a temporal northward shift in populations over the last three decades despite the recent cooling trend. Model results for local and shelf-wide indices showed that survey time lag and cold pool extent had a greater effect on spatial distribution than population abundance, suggesting that density-independent mechanisms play a major role in shaping distribution patterns on the eastern Bering Sea shelf. The area enclosed by the 1 °C isotherm most commonly affects both local and shelf-wide spatial indices suggesting that 1 °C is a more important boundary for describing temperature preferences of eastern Bering Sea bottom fishes and crabs than is the 2 °C isotherm used for designating the physical boundary for the cold pool.     

Bottom Boundary Layer Characteristics in the Hooghly Estuary Under Combined Wave-Current Action

The development of a theoretical model for estimating bottom boundary layer characteristics in the Hooghly estuary, located in the east coast of India, under combined effects of waves and currents is reported. Three numerical models, viz a depth averaged hydrodynamic model, SWAN wave model, and bottom boundary layer model, were integrated. In the bottom boundary layer parameters, maximum bottom stress, effective friction factor, and near-bed velocity both during ebb and flood phases of the tidal forcing are investigated and validated for the Haldia channel. The close match seen from results signifies applicability of this model for entire Hooghly basin.     

利用反射地震和多波束资料研究南海西北部麻坑的结构特征与成因

麻坑通常是由海底流体逸散形成的一种海底表面的残留地貌.本文所研究的区域主要位于南海的西北部,包括琼东南盆地的西南部和中建南盆地的中北部.该区域海底表面主要覆盖细粒沉积物,并且底流活动强烈,底流水道发育,为麻坑的形成和发育提供了有利条件.麻坑发育的主要因素是流体逸散系统,本文通过反射地震资料在本区发现了断层、气烟囱、泥火山、泥底辟、声空白/声混浊、强反射等多种与流体逸散相关的指示特征.麻坑的几何特征随着区域的不同会有较大变化.首先本区麻坑的尺寸跨度较大,与底流水道伴生的麻坑和广乐隆起的麻坑表面宽度通常是几十米到数百米,其他区域麻坑的表面宽度通常可达数千米,被称为巨型麻坑.其次本区麻坑的表面形态复杂多样,有圆形、椭圆形、新月形、环形等.各种不同的形态有可能指示了麻坑的不同发育阶段,新月形麻坑可能发育程度较低,其次是环形,圆形则相对较为成熟.据此推断发育程度较低的新月形麻坑有可能是活动麻坑,而地震海洋学的资料也倾向于证实这一点.     

Variation of overtides by wave enhanced bottom drag in a North Florida tidal inlet

Month-long observations of waves and tidal currents at Ponce de Leon Inlet, North Florida are used to investigate the importance of wave-induced bottom drag as a mechanism for overtide generation in estuaries. While bottom drag can in theory lead to overtide generation, in practice, resolving unambiguously this effect is difficult as it tends to be overshadowed by the stronger effect of diurnal–semidiurnal tidal variance. Bottom boundary layer numerical simulations based on observational data suggest that waves can cause the bottom drag experienced by currents to increase by a factor of 1.7, compared with relatively calm conditions. Despite the relatively short duration and limited scope of the experiment, the analysis suggests that overtide modulations (East–West velocity components of the 5th and 6th diurnal constituents) are correlated with wave-enhanced drag trends. Therefore, wave-enhanced bottom drags may be enhancing generation of overtides. Further work is necessary to understand the scope and the strength of this mechanism, in relation to the characteristics (e.g., flow direction) of individual overtides.     

海底地震仪对海上地震定位精度的提升作用——以南澳外海域M_L2.8级地震为例

由于海底地震台站的缺乏,如何提高海域地震定位的精度是目前地震学家面临的问题之一。南海北部陆缘作为板内地震的活跃带,其微震活动在华南沿海和近海海域频发,海上由于未布设相应的地震台网,因此对近海海域地震尤其是微震的定位精度极低。利用2012年南海东北部海陆地震联测期间两台海底地震仪(Ocean Bottom Seismographs,OBS)所记录到的南澳外海域发生的ML2.8级地震为例,对比分析OBS数据加入前后对地震定位结果的影响。这是首次在南海北部陆缘利用OBS联合陆上地震台网对天然地震进行定位的对比研究,结果说明了近海海域OBS的布设将会对我国沿海地震定位精度的提升、地震活动性的特征以及海域断裂构造的研究具有极其重要的意义。     

Wave- and current-induced bottom shear stress distribution in the Gulf of Lions

Simulations of both currents and waves were performed throughout the year 2001 to assess the relative contribution of each to their overall erosive potential on the Gulf of Lions shelf. Statistical analysis of bottom shear stress (BSS) was compared to sediment grain-size distribution on the bottom. The hydrodynamic features of the bottom layer coincide with the distribution of surficial sediments, and three areas with different hydro-sedimentary characteristics were revealed. (i) The sandy inner shelf (<30 m) area is a high-energy-wave dominated area but may be subjected to intense current-induced BSS during on-shore winds along the coast and during continental winds mainly in the up-welling cells. (ii) The middle shelf (30–100 m) is a low-energy environment characterised by deposition of cohesive sediments, where the wave effect decreases with depth and current-induced BSS cannot reach the critical value for erosion of fine-grained sediments. (iii) The outer shelf, which has a higher bottom sand fraction than the middle shelf, may be affected by strong south-westward currents generated by on-shore winds, which can have an erosive effect on the fine-grained sediments.     

Unusual behavior of the Kuroshio Current System from winter 1996 to summer 1997 revealed by ADEOS-OCTS and other data— Suggestion of topographically forced alternating-jet instability

While the Advanced Earth Observing Satellite (ADEOS) was operating, the Kuroshio and the Kuroshio Extension, or the Kuroshio Current System, exhibited unusual behavior from the winter of 1996 to the summer of 1997. This behavior of the Kuroshio Current System has been closely studied using a time series of satellite observation images of SST and ocean color obtained by ADEOS-OCTS, reinforced by SST images obtained by NOAA-AVHRR. Our findings include (i) a long lasting, very southerly path of the Kuroshio Extension; (ii) a Kuroshio path very distant from Japan with the following alternating-jet-like north-south flow pattern of the Kuroshio Extension, which occurred twice, once in February and once in April 1997, as independent events and which was observed to be affected by the bottom topography of the Izu-Ogasawara Ridge and Trench, and of the Japan Trench; (iii) cutting off of a cold water mass after the February event; and (iv) the formation of a vortex pair after the April event. A new mechanism is suggested for the formation of the alternating-jet flow pattern: a topographically forced alternating-jet instability (AJI). An SST-Chlorophyll Diagram (T-Chl Diagram) generated using simultaneous data from a single satellite is useful for analyzing the water mass structure of this region, including biological processes.     

南海东部马尼拉俯冲带深部结构新认识

2015—2018年, 国家自然科学基金重大研究计划“南海深海过程演变”的重点支持项目“南海东部马尼拉俯冲带深部结构探测与研究”以马尼拉俯冲带为研究重点, 从深部地球物理的角度探索南海形成演化史与运行规律。项目执行期间, 在国家基金委共享航次协助下, 先后开展和参与5次综合地球物理探测, 共投放海底地震仪(Ocean Bottom Seismometer, OBS)台站73台次, 海底电磁仪(Ocean Bottom ElectroMagnetometers, OBEM)仪器5台次, 累积放炮达13872炮, 成功获得了60台OBS数据和5台OBEM数据。同时, 取得了一系列创新性研究成果: (1)基于人工地震探测及天然地震层析成像结果, 确定南海东北部的地壳属性为受到张裂后期岩浆活动影响的减薄陆壳(12~15km), 划分了南海北部陆缘洋陆边界(Continent-Ocean Boundary, COB); (2)根据多道地震反射剖面, 划分了马尼拉俯冲带北部增生楔前缘的精细结构; (3)圈定了南海停止扩张时洋壳范围; (4)初步构建了南海与菲律宾海板块构造演化模型。本项目为重大研究计划“南海深海过程演变”核心科学问题(海底扩张的年代与过程)提供了实质性的证据, 同时为南海构造演化生命史的“骨架”提供了重要的基础数据, 具有深远的科学意义。     

与电子产品安全有关的温度、湿度、气压条件分析

利用30年气象观测资料,对与电子产品的生产、储存、运输和安全使用有关的特殊温度、湿度、气压等气象环境条件进行了统计分析。     

安徽省突发气象灾害预警信号制作系统

介绍了国内及安徽省预警信号发布制作工作的现状,阐述了安徽省气象台突发气象灾害预警信号制作系统的设计思路、流程结构和主要功能。该系统设计合理,并利用计算机软件编程技术完成人机交互的系统界面,可以方便快捷地生成图文并茂的预警信号发布内容,解决突发气象灾害预警信号制作工作的及时性、一致性、完整性问题。