Variation of particulate organic carbon and its relationship with bio-optical properties during a phytoplankton bloom in the Pearl River estuary

In this study, variations in the particulate organic carbon (POC) were monitored during a phytoplankton bloom event, and the corresponding changes in bio-optical properties were tracked at one station (114.29°E, 22.06°N) located in the Pearl River estuary. A greater than 10-fold increase in POC (112.29-1173.36 mg m⁻³) was observed during the bloom, with the chlorophyll a concentration (Chl-a) varying from 0.984 to 25.941 mg m⁻³. A power law function is used to describe the relationship between POC and Chl-a, and the POC:Chl-a ratio tends to change inversely with Chl-a. Phytoplankton carbon concentration is indirectly estimated using the conceptual model proposed by Sathyendranath et al. (2009), and this carbon is found to contribute 47.21% (±10.65%) to total POC. The estimated carbon-to-chlorophyll ratio of phytoplankton in diatom-dominated waters is found to be comparable with results reported in the literature. Empirical algorithms for determining the concentrations of Chl-a and POC were developed based on the relationships of these variables with the blue-to-green reflectance ratio. With these bio-optical models, the levels of particulate organic carbon and Chl-a could be predicted from the radiometric data measured by a marine optical buoy, which showed much more detailed information about the variability in biogeochemical parameters during this bloom event.     

遥感信息中地震灾情危险等级在线应急评定方法研究

利用GIS技术对地震危险等级进行评定时,由于其地形控制点选取合理性较差,导致其所采集遥感图像清晰度较低,地震等级评定不够精准。针对此问题提出一种新的地震灾情遥感信息危险等级在线应急评定方法。利用图像几何校正法,对遥感图像进行分幅裁剪,基于裁剪结果选取地面控制点,提取有价值遥感数据信息,建立遥感解译评估指标。将推导出的综合震灾指数引入到指标中,将各个评价单元的信息进行等级排序和划分,完成地震灾情遥感信息危险等级在线应急评定。仿真实验中,对所提方法和GIS地震危险等级评定方法进行有效性对比测试。实验结果表明,地震灾情遥感信息危险等级在线应急评定方法提升了灾情地形控制点选取的合理性,使获取的遥感图像更清晰,灾情等级评定结果更精准。     

Relationship between the equilibrium morphology of river islands and flow-sediment dynamics based on the theory of minimum energy dissipation

River islands are vital geomorphic units in alluvial rivers, and the variation of their morphology and position plays a significant role in regulating flow-sediment transport and channel stability. Based on the theories of minimum energy dissipation theory of fluid movement and river morphodynamics, this study uses the river islands in anabranching channels to analyze the relationship between the shape coefficient of river island and the flow-sediment dynamics under stable equilibrium conditions...     

Geochronology and Hf–Fe isotopic geochemistry of the Phanerozoic mafic–ultramafic intrusions in the Damiao area,northern North China Craton: Implications for lithospheric destruction

Timing and source of several Fe-mineralized mafic-ultramaficintrusions in the Damiao area are investigated here by coupling new geochronological and Hf–Fe isotopic data with previous results. Although regarded as a Late Paleoproterozoic assemblage previously, two ～140 Ma intrusions are recognized by zircon U–Pb dating, indicating emplacement of these intrusions from Middle Devonian to Early Cretaceous times. Both Hf and Fe isotopic features lead to the conclusion that distinct mantle components contributed to their magma generation. As the first magmatic phase, the ～395 Ma intrusions were mainly derived from the slightly-enriched SCLM that was prevalent during the Paleozoic. However, asthenospheric material was strongly involved in the formation of the ～215 Ma Gaositai intrusion. Therefore, the initiation of lithospheric destruction in the northern NCC is inferred to have occurred in Late Triassic time, triggered by post-orogenic extension following the ～250 Ma collision between the Siberian Craton and the NCC. The ～140 Ma intrusions originated from a significantly-enriched mantle component probably resided in the predominant slightly-enriched SCLM. This mantle source would have melted in the Late Mesozoic, when the thin lithosphere enabled enhanced heat transfer from the asthenosphere. In summary, these distinct mantle sources of mafic–ultramafic magmatism provide a record of mantle heterogeneity and the gradual upward migration of the lithosphere–asthenosphere boundary during lithospheric destruction.     

金属护栏对洛阳地震台地电阻率干扰定量分析

自2018年12月起,因洛阳地震台测区内安装金属护栏,该台地电阻率出现异常变化.为正确评估此次影响,结合洛阳地震台电测深曲线、岩性资料建立了三维水平层状结构模型,利用有限元法计算了测区内金属护栏对洛阳地震台地电阻率观测的影响.同时,建立典型H型电性结构模型,分析了不同属性的金属导线对地电阻率观测的影响.结果 显示:...     

Isolating spatiotemporally local mixed Rossby-gravity waves using multi-dimensional ensemble empirical mode decomposition

Climate Dynamics - Tropical waves have relatively large amplitudes in and near convective systems, attenuating as they propagate away from the area where they are generated due to the dissipative...     

Influences of tropical–extratropical interaction on the multidecadal AMOC variability in the NCEP climate forecast system

We have examined the mechanisms of a multidecadal oscillation of the Atlantic Meridional Overturning Circulation (AMOC) in a 335-year simulation of the Climate Forecast System (CFS), the climate prediction model developed at the National Centers for Environmental Prediction (NCEP). Both the mean and seasonal cycle of the AMOC in the CFS are generally consistent with observation-based estimates with a maximum northward volume transport of 16?Sv (10⁶?m³/s) near 35°N at 1.2?km. The annual mean AMOC shows an intermittent quasi 30-year oscillation. Its dominant structure includes a deep anomalous overturning cell (referred to as the anomalous AMOC) with amplitude of 0.6?Sv near 35°N and an anomalous subtropical cell (STC) of shallow overturning spanning across the equator. The mechanism for the oscillation includes a positive feedback between the anomalous AMOC and surface wind stress anomalies in mid-latitudes and a negative feedback between the anomalous STC and AMOC. A strong AMOC is associated with warm sea surface temperature anomaly (SSTA) centered near 45°N, which generates an anticyclonic easterly surface wind anomaly. This anticyclonic wind anomaly enhances the regional downwelling and reinforces the anomalous AMOC. In the mean time, a wind-evaporation-SST (WES) feedback extends the warm SSTA to the tropics and induces a cyclonic wind stress anomaly there, which drives a tropical upwelling and weakens the STC north of the equator. The STC anomaly, in turn, drives a cold upper ocean heat content anomaly (HCA) in the northern tropical Atlantic and weakens the meridional heat transport from the tropics to the mid-latitude through an anomalous southward western boundary current. The anomalous STC transports cold HCA from the subtropics to the mid-latitudes, weakening the mid-latitude deep overturning.     

夜间灯光支持下江西省典型城市发展动态监测

夜间灯光遥感与城市空间结构和经济发展具有较强的相关性.本文采用2012—2019年精细处理的美国国家极轨业务环境卫星(National Polar-Orbiting Partnership,NPP)搭载的可见光红外成像辐射仪(Visible InfraredImaging RadiometerSuite,VIIRS)夜...     

川西拉拉含矿镁铁质层状岩体的成因及构造背景

川西拉拉含矿镁铁质层状岩体位于扬子地块西缘,构造环境复杂,关于其成因机制及岩浆源区的问题至今仍缺乏系统的研究。文章针对该岩体七个岩相带,进行了主、微量元素和Sr-Nd同位素分析,结果表明,七个岩相带（YWS-1—YWS-7）是岩浆经历不同的演化过程而形成的。其中,第五相带SiO₂含量高（42.95%~44.07%）,MgO含量低（1.62%~1.89%）,稀土总量明显偏低（295.32×10-6~366.36×10-6）,Cr、Ni含量偏低,87Sr/86Sr为0.7391~0.7812,是受到地壳混染所致;其它相带Mg#值高（0.54~0.74）,稀土总量偏高（672.53×10-6~986.66×10-6）,87Sr/86Sr为0.7087~0.7097,显示岩石圈地幔源区特征。结合区域地质背景分析,认为该层状岩体产生于大陆裂谷构造环境,岩浆来源于岩石圈地幔源区,演化过程中结晶分异和多次脉动作用相伴。这一活动过程与新元古时期扬子板块西缘的超级地幔柱活动有关。      

花岗质岩石的基本问题

当代地球科学的两个前缘领域一个是地球的早期历史，一个是地球的深部过程，这两个问题都与花岗质岩石紧密相关。花岗质岩石主要由石英、斜长石和碱性长石组成，并因此具有较低的密度。这种性质决定了花岗质岩石具有正的浮力，记录了很长的地球演化历史。因此，花岗岩类是地质学最复杂的话题之一，因为其源区岩石多种多样和形成过程非常复杂。本文的目的是帮助普通旅游者识别花岗质岩石及其重要意义。通常，花岗岩（狭义）被定义为由石英（〉20％，按体积计算）和长石（碱性长石大于斜长石）组成的深成岩。但是，地质学家常常将特征与花岗岩（狭义）类似的深成岩称为花岗质岩石或花岗岩类，也就是广义花岗岩。因此，花岗岩类是深成岩的一个大类，包括象花岗闪长岩、二长花岗岩、正长花岗岩、英云闪长岩等这样的岩石。火成岩的多样性不仅仅取决于岩浆作用过程，而且也取决于岩浆形成过程。岩浆的产生是源区岩石部分熔融的结果，因而火成岩的化学成分取决于源区成分、熔融温度和压力、挥发分以及熔融程度。尽管岩浆作用过程对火成岩的成分具有重要影响，花岗质岩石多样性的关键因素却是部分熔融作用。基于此，岩石学家更注意花岗质岩浆的起源而不是它们的演化。花岗质岩浆虽然起源于地壳，却是受地幔热引擎的驱动。因此，花岗质岩石也记录了大量地球深部过程的信息。