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   

Temporal trends of bulk precipitation and stream water chemistry (1977–1997) in a small forested area,Krusné hory,northern Bohemia,Czech Republic     

N. E. Peters  Jiri Cerny  Miroslav Havel  Radovan Krejci 《水文研究》1999,13(17):2721-2741

The Krusné hory (Erzgebirge or Ore Mountains) has been heavily affected by high atmospheric pollutant deposition caused by fossil fuel combustion in an adjacent Tertiary coal basin. Long‐term routine sampling of bulk precipitation (1977–1996) and stream water (1977–1998) in a forested area on the south‐eastern slope of the mountains were used to evaluate trends and patterns in solute concentration and flux with respect to controlling processes. From 1977 to 1996, the annual volume‐weighted Ca²⁺ and SOconcentrations decreased in bulk precipitation. However, after 1989, when a pronounced and continuous decrease occurred in coal production, annual volume‐weighted concentrations decreased for most solutes, except H⁺. The concentration decreases were marked, with 1996 levels at or below 50% of those in 1989. The lack of a trend in H⁺ is attributed to similar decreases in both acid anions and neutralizing base cations. Stream water concentrations of most solutes, i.e. H⁺, Ca²⁺, Mg²⁺, SONOwere highest at the onset of sampling in 1977, decreased markedly from 1977 to 1983 and decreased more gradually from 1983 to 1998. The spruce forest die‐back and removal reduced dry deposition of these solutes by reducing the filtering action, which was provided by the forest canopy. A notable decrease in stream water Ca²⁺ concentrations occurred after 1995 and may be due to the depletion of Ca²⁺, which was provided by catchment liming in 1986, 1988 and 1989. Solute flux trends in bulk atmospheric deposition and stream water generally were not significant and the lack of trend is attributed to the large interannual variability in precipitation quantity and runoff, respectively. All solutes except Na⁺ varied seasonally. The average seasonal concentrations varied between the solutes, but for most solutes were highest in winter and spring and lowest in summer, correlating with the seasonal trend in runoff. For Ca²⁺, Mg²⁺ and SOthe concentration minimum occurs in September and the maximum occurs in February or March, correlating with the seasonal baseflow. These solutes are primarily controlled by the contribution of soil water and groundwater to stream flow. During snowmelt, the meltwater generally causes concentrations to decrease as soil water and groundwater are diluted. For NO₃ , average minimum concentrations occur in August at the end of the growing season concurrent with the lowest stream flow, and the maximum occurs in February and March with high stream flow during snowmelt. Seasonal stream water NOconcentration variations are large compared with the long‐term decrease. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

台风活动的气候突变   总被引：17，自引：5，他引：17  

陈兴芳  晁淑懿 《热带气象学报》1997,13(2):97-104

通过近４０个西太平洋和南海台风资料的分析，发现台风活动有着明显的气候振动，并且在７０年代前期发生气候突变，表现为７０年代前期以前台风数增多，台风偏强趋势；７０年代中期以后则相反，为台内数减少台风偏弱趋势。８０年代末台风数再次转为增多趋势，但  相似文献   

Six decades of ecohydrological research connecting landscapes and riverscapes in the Girnock Burn,Scotland: Atlantic salmon population and habitat dynamics in a changing world     

C. Soulsby  I. A. Malcolm  D. Tetzlaff 《水文研究》2024,38(3):e15105

Long-term data are crucial for understanding ecological responses to climate and land use change; they are also vital evidence for informing management. As a migratory fish, Atlantic salmon are sentinels of both global and local environmental change. This paper reviews the main insights from six decades of research in an upland Scottish stream (Girnock Burn) inhabited by a spring Atlantic salmon population dominated by multi-sea-winter fish. Research began in the 1960s providing a census of returning adults, juvenile emigrants and in-stream production of Atlantic salmon. Early research pioneered new monitoring techniques providing new insights into salmon ecology and population dynamics. These studies underlined the need for interdisciplinary approaches for understanding salmon interactions with physical, chemical and biological components of in-stream habitats at different life-stages. This highlighted variations in catchment-scale hydroclimate, hydrology, geomorphology and hydrochemistry as essential to understanding freshwater habitats in the wider landscape context. Evolution of research has resulted in a remarkable catalogue of novel findings underlining the value of long-term data that increases with time as modelling tools advance to leverage more insights from “big data”. Data are available on fish numbers, sizes and ages across multiple life stages, extending over many decades and covering a wide range of stock levels. Combined with an unusually detailed characterization of the environment, these data have enabled a unique process-based understanding of the controls and bottlenecks on salmon population dynamics across the entire lifecycle and the consequences of declining marine survival and ova deposition. Such powerful datasets, methodological enhancements and the resulting process understanding have informed and supported the development of fish population assessment tools which have been applied to aid management of threatened salmon stocks at large-catchment, regional and national scales. Many pioneering monitoring and modelling approaches developed have been applied internationally. This history shows the importance of integrating discovery science with monitoring for informing policy development and assessing efficacy of management options. It also demonstrates the need to continue to resource long-term sites, which act as a focus for inter-disciplinary research and innovation, and where the overall value of the research greatly exceeds the costs of individual component parts.  相似文献   

昭通市一次大范围暖区暴雨天气过程分析          下载免费PDF全文

沈茜 《中低纬山地气象》2020,44(2)

利用NCEP/NCAR 1°×1°再分析资料、昭通多普勒雷达资料 、自动站实时观测资料等,分析云南省昭通市夏季的一次伴有大范围短时强降水的暖区暴雨过程。结果表明：这是一次发生在有利的天气尺度背景下,由持续存在的地面辐合线触发抬升产生的暖区对流性降雨过程;这次过程的水汽来源于孟加拉湾、南海和西太平洋,同时700hPa水汽输送与降水的落区和量级密切相关,水汽输送越好,降雨量级越大;长期维持的上干冷下暖湿的不稳定层结,配合有利的水汽条件和适当的物理量场导致了此次连续性强对流天气的发生;垂直上升速度的大值区和降雨量级的大值区并不是一一对应关系,可以用来表征降雨的状态,但是不能用来定量表征降雨量级;持续存在的“逆风区”有利于连续性的短时强降水的发生;昭通市低层偏东风辐合导致的暖区对流性降水过程中,地形的辐合抬升起到了重要的作用。  相似文献   

用实验方法研究水泥石动态断裂韧性   总被引：1，自引：0，他引：1  

王通  王强  于长滨  王祥林 《地震工程与工程振动》2006,26(4):250-254

为了减轻射流侵彻对水泥环的破坏,改善界面的密封胶结性能,必须对现有的水泥石进行改性研究。根据超混复合材料的原理,我们在水泥石的配比中增加几种填料,通过填料影响改变水泥石的动态断裂韧性。将水泥石制成短棒试件,用分段式Hopk inson压杆对几种改性配方的水泥石的动态断裂韧性进行实验测定,给出了部分实验结果。采用反射式动态焦散线方法,对六种水泥石材料的动态断裂韧性进行了实验研究,给出了实验结果。并比较了短棒实验和动态焦散线法测量动态断裂韧性的结果,两者吻合较好。研究表明:纤维增强是提高水泥石抗冲击性能的有效途径。  相似文献   

山西省汛期短历时强降水特征          下载免费PDF全文

周雅清  胡桃花  王弢  赵酉龙 《沙漠与绿洲气象(新疆气象)》2021,15(6):40-46

山西地形复杂,汛期降水集中,短时强降水易引发地质灾害及城市内涝,是制约社会经济发展和人民安居的重要因素。本文通过分析山西省2011~2016年290个高密度自动气象站逐时降水资料,结合本地强降水预警业务规定,根据致灾风险程度将短历时强降水分为四级,全面细致分析了各级强降水的时空变化特征,对强降水的精细化预报有指示意义。结果表明：短时强降水主要受纬度和地形影响,各级强降水的累计降水量和降水小时数大值区一般沿太行山脉和吕梁山脉展布；短时强降水在每日15～18时高发,到了夜间20～23时,出现第二峰值；城区一般性强降水比乡村区域偏多偏强。  相似文献   

改进型经验正交函数海洋声速剖面预报方法   总被引：1，自引：0，他引：1       下载免费PDF全文

韩梅  魏亮  周艳霞 《海洋科学》2009,33(1):30-33

鉴于深海温跃层以下往往声速值缺乏,声速剖面不完整的原因,提出一种声速剖面的预报方法:在传统经验正交函数预报法基础上,首先改进协方差矩阵的求解方法,将原始数据的空间信息和时间信息有效地融合到协方差矩阵中,通过由大量实测数据统计得出的时间函数的经验公式,得到合成剖面,将二者结合,把不完整剖面垂直向下延拓到海底,较为有效地解决了传统方法求解协方差矩阵和时间函数较粗糙的问题,给出了完整的海洋声速剖面的准确预报.实测数据检验结果表明,改进方法的预报精度比传统方法有了很大提高.  相似文献   

副热带高压控制下湖南两次短时暴雨发生及系统维持机制对比分析          下载免费PDF全文

兰明才  周莉  蒋帅  蔡荣辉  尹依雯 《气象科技》2022,50(4):512-525

利用地面自动站资料、多普勒天气雷达资料、卫星逐小时TBB资料及NCEP再分析资料，对2018年副高控制下湖南两次短时暴雨发生及维持机制进行分析。结果表明：①在水汽丰沛且有足够的不稳定能量和抬升条件下，强盛副高脊区反气旋环流内也可以触发短时暴雨天气，其大尺度环流形势特征和湖南典型暴雨过程有着较大差异；②对流性降水发生前，不稳定能量明显增强，中低层增湿明显，为暴雨提供能量与水汽条件；③两次过程分别受副高南侧热带气旋外围云系扰动和弱冷空气侵入影响，925 hPa形成弱扰动或者弱切变，配合地面中尺度辐合线，近地面动力抬升触发对流性降水，白天受太阳辐射影响，能够自由触发热对流。地形抬升也是重要触发机制，发生在迎风坡热对流占比84%；④两次短时暴雨的雷达回波为非常明显的低质心高效率的降水回波，环境风及其垂直风切变小，尽管不利于对流风暴有组织的发展，但雷暴单体移动缓慢，有利于同一地区长时间的强降水。  相似文献   

鲁西南2020年两次区域性大暴雨过程形成机制分析          下载免费PDF全文

李博  吕桂恒  高飞  刘飞  郭文明 《气象科技》2022,50(5):702-712

利用常规地面、高空观测和ERA5再分析数据，对鲁西南2020年7月22日（简称“7〖DK〗·22”过程）和8月6—7日（简称“8〖DK〗·6”过程）两次区域性大暴雨及伴随的短时强降水形成机制诊断分析。结果表明：“7〖DK〗·22”过程是一次地面气旋降水过程，大暴雨主要出现在气旋中心至移向右前部的倒槽内，短时强降水是对流不稳定触发后，惯性不稳定的增强造成。“8〖DK〗·6”过程是一次副高边缘暖区降水过程，大暴雨主要出现在低空急流的前端、地面辐合线附近，短时强降水由对流不稳定的触发和释放造成。“7〖DK〗·22”过程暖湿急流较强，水汽通量散度和动力条件显著强于“8〖DK〗·6”过程，超低空强辐合区、水汽通量散度辐合大值区、水平动能大值区边缘的强锋生区以及湿位涡MPV大值区边缘的|MPV2|小值区对短时强降水的出现区域指示较好。两次过程分析均表明垂直上升运动和深厚湿区的配合对短时强降水的出现时间指示较好。  相似文献