Characteristics of thermal finestructure in the southern Yellow Sea and the East China Sea from airborne expendable bathythermograph measurements     

Sunghyea Park  Peter C. Chu 《Journal of Oceanography》2008,64(6):859-875

Four surveys of airborne expendable bathythermograph with horizontal spacing of about 35 km and vertical spacing of 1 m extending from the surface down to 400 m deep are used to analyze thermal finestructures and their seasonality in frontal zones of the southern Yellow Sea and the East China Sea. Finestructure characteristics are different not only among fronts but also along the same front, implying different mixing mechanisms. Summer thermocline intrusions with thickness from few to 40 meters, generated by the vertically-sheared advection, are identified along the southern tongue of the Cheju-Yangtze Front (especially south of Cheju Island). The finestructures south of the Yangtze Bank (i.e. the western tip of the southern tongue) produced by strong along-frontal currents are not as rich as elsewhere in the southern tongue. The Cheju-Tsushima Front presents mixed finestructures due to confluent currents from various origins. The irregular-staircase finestructures in the Kuroshio region (below the seasonal thermocline), driven by double-diffusive mixing, show seasonal invariance and vertical/horizontal coherence. The strength of mixing related to finestructure is weaker in the Kuroshio region than in the Cheju-Tsushima Front or south of Cheju Island. The profiles in the Tsushima Warm Current branching area show large (∼50 m thick), irregular-staircase structures at the upper 230 m depth, which coincides roughly with the lower boundary of the maximum salinity layer. The finestructure at depths deeper 230 m is similar to that in the Kuroshio region. The possible mechanisms for generating the finestructures are also discussed.  相似文献   

BCC_CSM对北极海冰的模拟:CMIP5和CMIP6历史试验比较   总被引：1，自引：1，他引：0  

王松  苏洁  储敏  史学丽 《海洋学报》2020,42(5):49-64

本文利用北京气候中心气候系统模式(BCC_CSM)在最近两个耦合模式比较计划(CMIP5和CMIP6)的历史试验模拟结果,对北极海冰范围和冰厚的模拟性能进行了比较,结果表明:(1) CMIP6改善了CMIP5模拟海冰范围季节变化过大的问题,总体上更接近观测结果;(2)两个CMIP试验阶段中BCC_CSM模拟的海冰厚度都偏小,但CMIP6试验对夏季海冰厚度过薄问题有所改进。通过对影响海冰生消过程的冰面和冰底热收支的分析,我们探讨了上述模拟偏差以及CMIP6模拟结果改善的成因。分析表明,8?9月海洋热通量、向下短波辐射和反照率对模拟结果的误差影响较大,CMIP6试验在这些方面有较大改善;而12月至翌年2月,CMIP5模拟的北极海冰范围偏大主要是海洋热通量偏低所导致,CMIP6模拟的海洋热通量较CMIP5大,但北大西洋表层海流的改善才是巴芬湾附近海冰外缘线位置改善的主要原因。CMIP试验模拟的夏季海冰厚度偏薄主要是因为6?8月海洋热通量和冰面热收支都偏大,而CMIP6试验模拟的夏季海冰厚度有所改善主要是由于海洋热通量和净短波辐射的改善。海冰模拟结果的改善与CMIP6海冰模块和大气模块参数化的改进有直接和间接的关系,通过改变短波辐射、冰面反照率和海洋热通量,使BCC_CSM模式对北极海冰的模拟性能也得到有效提高。  相似文献   

Chemical composition and petrogenesis of plagioclases in plagioclase-phyric basalts from the Southwest Indian Ridge(51°E)     

李洁  初凤友  朱继浩  朱志敏  李小虎  王浩 《海洋学报(英文版)》2020,39(7):42-49

Electron microprobe analysis was conducted on plagioclase from the plagioclase ultraphyric basalts(PUBs)erupted on the Southwest Indian Ridge(SWIR)(51°E) to investigate the geochemical changes in order to better understand the magmatic processes occurring under ultraslow spreading ridges and to provide insights into the thermal and dynamic regimes of the magmatic reservoirs and conduit systems. The phenocryst cores are generally calcic(An_(74–82)) and are depleted in FeO and MgO. Whereas the phenocryst rims(An_(67–71)) and the plagioclase in the groundmass(An_(58–63)) are more sodic and have higher FeO and MgO contents than the phenocryst cores. The crystallization temperatures of the phenocryst cores and the calculation of the equilibrium between the phenocrysts and the matrix suggest that the plagioclase cores are unlikely to have crystallized from the host basaltic melt, but are likely to have crystallized from a more calcic melt. The enrichment in incompatible elements(FeO and MgO), as well as the higher FeO/MgO ratios of the outermost phenocryst rims and the groundmass, are the result of plagioclase-melt disequilibrium diffusion during the short residence time in which the plagioclase crystallized. Our results indicate that an evolved melt replenishing under the SWIR(51°E) drives the eruption over a short period of time.  相似文献   

“一带一路”沿线重点省份旅游经济高质量发展研究   总被引：1，自引：1，他引：0  

王松茂  褚玉静  郭安禧  郭英之 《地理科学》2020,40(9):1505-1512

从旅游资源转换效率的视角,以“一带一路”沿线18个重点省份为研究靶区,运用修正的DEA模型等方法探究2008—2017年的旅游经济增长质量的时空演变及发展趋势。研究结论有：① 10 a间,18个重点省份旅游资源转换效率均值仅为0.312,远未达到生产前沿面。② 经过邹检验（Chow test）,2014年为“一带一路”沿线18个重点省份旅游资源转换效率时间序列的突变点。③ 18个重点省份的旅游资源转换效率均存在σ收敛、绝对β收敛和条件β收敛;开放先行区、战略支点区未通过σ收敛检验、战略支点区未通过绝对β收敛。  相似文献   

Consistency of stress state,locations and source mechanisms of events induced by hydraulic fracturing: downhole monitoring          下载免费PDF全文

Zuzana Jechumtálová  Fangdong Chu  Gang Yu  Jan Procházka 《Geophysical Prospecting》2018,66(7):1315-1326

We present results of processed microseismic events induced by hydraulic fracturing and detected using dual downhole monitoring arrays. The results provide valuable insight into hydraulic fracturing. For our study, we detected and located microseismic events and determined their magnitudes, source mechanisms and inverted stress field orientation. Event locations formed a distinct linear trend above the stimulated intervals. Source mechanisms were only computed for high‐quality events detected on a sufficient number of receivers. All the detected source mechanisms were dip‐slip mechanisms with steep and nearly horizontal nodal planes. The source mechanisms represented shear events and the non‐double‐couple components were very small. Such small, non‐double‐couple components are consistent with a noise level in the data and velocity model uncertainties. Strikes of inverted mechanisms corresponding to the nearly vertical fault plane are (within the error of measurements) identical with the strike of the location trend. Ambient principal stress directions were inverted from the source mechanisms. The least principal stress, σ₃, was determined perpendicular to the strike of the trend of the locations, indicating that the hydraulic fracture propagated in the direction of maximum horizontal stress. Our analysis indicated that the source mechanisms observed using downhole instruments are consistent with the source mechanisms observed in microseismic monitoring arrays in other locations. Furthermore, the orientation of the inverted principal components of the ambient stress field is in agreement with the orientation of the known regional stress, implying that microseismic events induced by hydraulic fracturing are controlled by the regional stress field.  相似文献   

Concurrent Treatment of 1,4‐Dioxane and Chlorinated Aliphatics in a Groundwater Recirculation System Via Aerobic Cometabolism          下载免费PDF全文

Min‐Ying Jacob Chu  Peter J. Bennett  Mark E. Dolan  Michael R. Hyman  Aaron D. Peacock  Adria Bodour  Richard Hunter Anderson  Douglas M. Mackay  Mark N. Goltz 《Ground Water Monitoring & Remediation》2018,38(3):53-64

This research demonstrates that groundwater contaminated by a relatively dilute but persistent concentration of 1,4‐dioxane (1,4‐D), approximately 60 μg/L, and chlorinated aliphatic co‐contaminants (1.4 to 10 μg/L) can be efficiently and reliably treated by in situ aerobic cometabolic biodegradation (ACB). A field trial lasting 265 days was conducted at Operable Unit D at the former McClellan Air Force Base and involved establishing an in situ ACB reactor through amending recirculated groundwater with propane and oxygen. The stimulated indigenous microbial population was able to consistently degrade 1,4‐D to below 3 μg/L while the co‐contaminants trichloroethene (TCE) and 1,2‐dichloroethane (1,2‐DCA) were decreased to below 1 μg/L and 0.18 μg/L, respectively. A stable treatment efficiency of more than 95% removal for 1,4‐D and 1,2‐DCA and of more than 90% removal for TCE was achieved. High treatment efficiencies for 1,4‐D and all co‐contaminants were sustained even without propane and oxygen addition for a 2‐week period.  相似文献   

曹妃甸地震台网天然地震与人工爆破时频分析   总被引：1，自引：1，他引：0  

荣伟健  赵建明  董祎玮  孟令焕  符泽宇  王妍  李金  刘楚 《地震地磁观测与研究》2017,38(5):39-43

搜集2014—2015年曹妃甸测震台网记录的各类爆破与天然地震事件,基于Matlab软件,编制程序实现短时傅里叶变换,对比分析核爆炸、化学爆炸、矿爆炸与天然地震的特征,分析频率随时间的变化规律。研究结果表明,天然地震与爆破在频率范围、频率分布和时频聚集性等方面具有各自特点,主要表现在:天然地震的时频图"多峰"且复杂,频率分布范围更广,频率成分集中在S波段;人工爆破的时频图"少峰"且简单,频率范围较窄,频率成分集中在P波段。本文的研究成果能够为今后区分天然地震和爆破提供依据。  相似文献   

曹妃甸地震台网天然地震与爆破波形记录特征     

董祎玮  赵建明  李金  刘楚  任佳  王妍  符泽宇  荣伟健  孟令焕 《地震地磁观测与研究》2017,38(3):30-34

统计曹妃甸地震台网成立以来记录的地震波形资料,对比天然地震和化学爆炸、矿爆的波形,发现天然地震与爆破震相特征在P波初动、周期、波形衰减及振幅等方面有很大不同,并对波形进行频谱分析,进一步识别天然地震及爆破。  相似文献   

Controls of preferential orientation of earthquake- and rainfall-triggered landslides in Taiwan's orogenic mountain belt     

Yi-Chin Chen  Kang-Tsung Chang  Su-Fen Wang  Jr-Chuan Huang  Cheng-Ku Yu  Jien-Yi Tu  Hone-Jay Chu  Cheng-Chien Liu 《地球表面变化过程与地形》2019,44(9):1661-1674

Landsliding usually occurs on specific hillslope aspect, which may reflect the control of specific geo-environmental factors, triggering factors, or their interaction. To explore this notion, this study used island-wide landslide inventories of the Chi-Chi earthquake in 1999 (M_W = 7.6) and Typhoon Morakot in 2009 in Taiwan to investigate the preferential orientation of landslides and the controls of landslide triggers and geological settings. The results showed two patterns. The orientations of earthquake-triggered landslides were toward the aspect facing away from the epicenter in areas with peak ground acceleration (PGA) ≥ 0.6 g and landslide ratio ≥ 1%, suggesting that the orientations were controlled by seismic wave propagation. Rainfall-triggered landslides tended to occur on dip slopes, instead of the windward slopes, suggesting that geological settings were a more effective control of the mass wasting processes on hillslope scale than the rainfall condition. This study highlights the importance of the endogenic processes, namely seismic wave and geological settings, on the predesigned orientation of landslides triggered by either earthquake or rainfall, which can in turn improve our knowledge of landscape evolution and landslide prediction. © 2019 John Wiley & Sons, Ltd.  相似文献   

基于水华蓝藻固有光学特性的主要类群定量识别方法     

褚乔  张壹萱  张玉超  马荣华  胡旻琪 《湖泊科学》2021,33(1):74-85

蓝藻水华是湖泊水体富营养化的重要特征之一,不同水华蓝藻类群形成的水华特征、危害及其治理方法差异显著.因此,如何快速、准确地掌握不同蓝藻类群的时空分布特征成为实施富营养化湖泊污染治理与生态恢复、蓝藻生态灾害预测预警中一个亟待解决的科学问题.本研究基于纯藻种实验室培养和室内光学控制实验,在微囊藻(Microcystis)、鱼腥藻(Dolichospermum)、束丝藻(Aphanizomenon)3种主要水华蓝藻固有光学特性的基础上,通过甄别不同水华蓝藻的吸收、散射和后向散射光谱的特征波段,构建了基于吸收和散射特性的5种水华蓝藻类群的非线性最优化定量识别模型,其中,基于440、620和675 nm 3个波段吸收的a-CIM 440,620,675具有较为稳定的定量识别能力;并基于野外实测光学特性数据,实现了巢湖主要水华蓝藻类群的定量监测,初步分析了巢湖主要水华蓝藻类群的时空分布特性.研究表明,巢湖的水华蓝藻以鱼腥藻、微囊藻为主,束丝藻较少,鱼腥藻主要出现在温度较低的季节,微囊藻在夏季的西部湖区占优势;巢湖水华主要为微囊藻藻华和鱼腥藻藻华,且浓度较高的蓝藻主要存在于水体表面以下20 cm范围内;微囊藻和鱼腥藻在非藻华断面垂向上均匀分布.本研究可为富营养化湖泊蓝藻水华预测预警以及相关管理部门决策提供重要的理论依据和科学支撑.  相似文献