从气旋和反气旋谈正、负阻尼     

刘式达  刘式适  付遵涛 《大气科学》2014,38(6):1041-1043

在定常条件下,利用简化的大气运动控制方程,分析了气旋与反气旋的基本特征。在此基础上,利用常微分方程的定性分析与求解,获得了气旋和反气旋轨道的解析解。接合气旋与反气旋的基本特征,论证了正负阻尼在气旋和反气旋运动中具体体现,并从物理机理上说明产生气旋和反气旋运动中正负阻尼的差异在于水平辐合在低层的不同。  相似文献   

大连市负氧离子浓度分布及预测模型的建立   总被引：6，自引：1，他引：5       下载免费PDF全文

丛菁  孙立娟 《气象与环境学报》2010,26(4):44-47

利用2008—2009年大连市逐日负氧离子实况资料,分析了负氧离子季、月和日变化特征及其与相关气象要素的关系。结果表明：负氧离子浓度具有明显的季节变化,冬季最大,夏季最小;而气温和PM10等是影响大连市负氧离子浓度的关键因素。运用逐步回归方法,求得各季节负氧离子的预报方程,实现了预报的定量化。经检验,预报方程效果显著,在预报业务中具有实际参考价值。  相似文献   

汶川地震前龙门山断裂带闭锁程度和滑动亏损分布研究   总被引：16，自引：6，他引：10       下载免费PDF全文

赵静  江在森  武艳强  刘晓霞  魏文薪  李强 《地球物理学报》2012,55(9):2963-2972

利用1999—2007期GPS水平速度场数据,采用Defnode负位错反演程序估算了龙门山断裂在汶川地震前的闭锁程度和滑动亏损分布,结合龙门山断裂带附近地表水平应变率场结果,综合分析了震前地壳变形特征.反演结果表明,震前龙门山断裂中北段处于完全闭锁状态,闭锁深度达到21 km(闭锁比例0.99)左右,垂直断层方向的挤压滑动亏损速率约为2.2 mm/a,平行断层方向的右旋滑动亏损速率约为4.6 mm/a.龙门山断裂南段只有地表以下12 km闭锁程度较高(闭锁比例0.99),垂直断层方向滑动亏损速率约为1.4 mm/a,平行断层方向滑动亏损速率约为4.6 mm/a;在12~16 km处闭锁比例约为0.83,垂直断层方向滑动亏损速率约为1.2 mm/a,平行断层方向滑动亏损速率约为3.8 mm/a;在16~21 km处闭锁比例约为0.75,垂直断层方向滑动亏损速率约为1.1 mm/a,平行断层方向滑动亏损速率约为3.5 mm/a.在21~24 km处整条断裂均逐步转变为蠕滑.上述反演结果与区域应变计算获得的龙门山断裂带中北段整体应变积累速率较低、南段应变积累速率较高相一致,均表明中北段闭锁程度高、南段闭锁程度稍低,该特征可以较好地解释汶川地震时从震中向北东向单向破裂现象.  相似文献   

松辽盆地南部HX井上白垩统青山口组黑色泥岩的矿物组成与自生微晶石英成因   总被引：1，自引：0，他引：1  

刘立  王力娟  杨永智  于志超 《吉林大学学报(地球科学版)》2012,42(5):1358-1365

泥质岩的矿物组成和成岩作用是制约其作为CO₂地质封存的盖层封闭能力和作为页岩气储层具易压裂性质的重要原因。通过地球化学分析、X-射线衍射分析和扫描电镜观测及能谱测定,确定了松辽盆地南部HX井上白垩统青山口组泥岩的矿物组成,识别出了蒙皂石转变伊利石反应过程中形成的亚微米级自生微晶石英。研究表明：HX井上白垩统青山口组泥岩的母岩岩石类型和风化效应一致,泥岩主要由黏土矿物、钠长石和石英组成,钾长石少量;黏土矿物以伊利石/蒙皂石混层为主,其次为绿泥石;脆性矿物（钠长石、石英和钾长石）的平均质量分数为44.43%,黏土矿物平均质量分数为54.26%。蒙皂石转变伊利石反应过程中形成的亚微米级微晶石英单晶呈自形－半自形粒状,集合体呈巢状,分布于伊利石/蒙皂石混层黏土矿物的微孔隙中。以伊利石/蒙皂石混层矿物为主、且存在一定量的自生微晶石英的泥岩盖层（例如HX井青山口组泥岩）将有助于注入CO₂的长期封存。HX井青山口组泥岩中的脆性矿物含量符合工业价值页岩气的储层标准,而黏土矿物含量则相差较多。  相似文献   

Stream turbidity responses to storm events in a pristine rainforest watershed on the Coral Coast of southern Fiji     

《国际泥沙研究》2016,(4):279-290

On the Coral Coast of Viti Levu Island in Fiji, inadequate knowledge of suspended sediment delivery patterns in small pristine coastal watersheds hinders any future assessment of accelerated erosion in disturbed areas nearby. This study adopts a rainfall–stream turbidity monitoring approach in the Votua Creek, which drains a small, steep but minimally-disturbed coastal rainforest catchment. Storm rainfall characteristics, stream depth and water turbidity were continuously monitored over one complete Fiji wet season from October 2009 to April 2010. The aim was to evaluate whether these parameters provide sufficient information to illustrate basic features of storm–sediment transport responses, in the case of limited stream gauging and very simple sediment rating curves. This is important because Pacific Island nations like Fiji do not have the resources to initiate long-term gauging and sediment sampling pro-grammes across numerous small catchments.
A significant power function demonstrates that turbidity (T) is a suitable proxy for total suspended solids (TSS) for turbidity measurements above 5 NTU, with TSS?0.930T1.111 (r?0.98, Po0.001). Over the study period, 10 individual storms 11.2–120.1 mm in size produced a‘significant turbidity response’ (STR) in the Votua Creek. Rainfall parameters (totals and intensities) showed positive linear relationships (r ? 0.72–0.94) with stream turbidity parameters (mean, maximum, duration), whilst relationships of similar strength (r ? 0.76–0.98) were also derived between stream flow depth and turbidity. This implies that for small rainforest watersheds in Fiji, rainfall parameters offer no substantial disadvantage over flow as predictors of stream sediment responses to major storms. Event-based analysis revealed that negative (anticlockwise) hysteresis is a typical flow–turbidity pattern for STR events. Negative hysteresis is produced when secondary episodes of renewed (heavy) rainfall occur after maximum intensity, in the later phase of storm events. Tropical Cyclone Mick in December 2009 generated the largest flood and the greatest turbidity response (Tmax ? 1021 NTU, Tmean ? 207 NTU). This concurs with earlier work confirming that tropical cyclones are the most important events for sediment transport in Fiji stream networks.  相似文献   

A modelling study of the effect of ice particle sizes and relative velocity on ice crystal/graupel collisional charge transfer     

B. Tsenova  R. Mitzeva  C. Saunders 《Atmospheric Research》2009,91(2-4):250-258

The effect of ice particle sizes and relative velocity on the sign of charge transfer during graupel/ice crystal interactions in thunderstorms is considered based on the concept of the Relative Growth Rate Hypothesis that the ice surface growing faster by water vapour diffusion charges positively. Diffusional growth rates of ice crystals and riming graupel particles are calculated for various particle sizes and velocities, and the sign of charging during crystal/graupel collisions is determined. The study reveals that larger graupel charges more negatively, while larger ice crystals, or higher relative velocity, lead to increased positive graupel charging.  相似文献   

北京地区负地闪回击转移的电荷量   总被引：1，自引：1，他引：0  

武智君  郄秀书  王东方  王宇 《气候与环境研究》2016,21(3):247-257

负地闪是闪电危害的主要来源,其对地转移电荷源特征和电荷量不仅对闪电放电机理的研究有重要意义,而且对雷电防护也具有重要的实际应用价值。为了研究具有典型城市下垫面环境的北京地区的闪电活动特征和放电强度,利用北京地区2011年两次雷暴过程的多站GPS(Global Position System)同步闪电地面电场变化定量观测资料,在考虑消除场地和环境因素对电场变化观测资料影响的基础上,基于蒙特卡洛数据处理方法和非线性最小二乘法拟合反演算法,定量研究了负地闪回击中和的电荷源位置和电荷量,并对回击特征与回击转移电荷源之间的关系进行了讨论,得到如下结果:(1)单次回击中和的电荷量为1.1~27.6 C,平均为8.6±5.2 C,不同序数回击转移电荷量的最小值基本不随回击序数的上升而变化,最大值和均值随回击序数的上升而减小;一次负地闪中和的总电荷量随着回击数的增加而增加。(2)负地闪回击数和回击时间间隔都呈对数正态分布,其中负地闪总数70.4%的多回击负地闪其回击间隔平均为99±95 ms,不同序数回击的时间间隔最小值随回击序数的上升基本不变,时间间隔最大值和均值随回击序数的上升而减小。(3)回击转移电荷量的均值随回击间隔的增加呈波动形式的逐渐上升;相邻回击转移电荷源的空间距离均值随回击间隔的增加而增大。  相似文献   

Influences of soil consolidation and pile load on the development of negative skin friction of a pile     

R.P. Chen  W.H. Zhou  Y.M. Chen   《Computers and Geotechnics》2009,36(8):1265-1271

Negative skin friction (NSF) along a pile caused by soil consolidation is of great concern to engineers. The development of NSF is time-dependent because soil consolidation is also time-dependent. In this paper, a numerical solution is provided for the development of negative skin friction of a pile in nonlinear consolidated soil under different loads on a pile top. A hyperbolic interface model is also developed. This model considers the development of shear strength during soil consolidation and loading–unloading scenarios at the pile–soil interface. One-dimensional nonlinear consolidation theory is invoked to estimate the soil settlement and shear strength. The distributions of NSF and the axial force along the pile are obtained using the differential quadrature method (DQM). The influences of soil consolidation and different pile loads on the negative skin friction of a pile are discussed.  相似文献   

Hard X-ray imaging via focusing optics with mosaic crystals     

F. Frontera  G. Pareschi 《Experimental Astronomy》1995,6(4):25-31

In spite of the tremendous potential of hard X-ray astronomy (>10 keV) for studying high energy phenomena in celestial objects, the current generation of direct-viewing telescopes is heavily noise limited. It can accurately study only the strongest sources. Thus focusing of hard X-rays is mandatory in order to overcome these sensitivity limitations. Several focusing techniques of hard X-rays (>10 keV) are under study. We will discuss the Bragg diffraction technique and the imaging performance of a concentrator configuration based on this technique. Apart from its unprecedented flux sensitivity, the Bragg concentrators show intrinsic capabilities as polarimeters.  相似文献   

中国主要河流干旱特性的统计分析   总被引：14，自引：0，他引：14  

丁晶  袁鹏 《地理学报》1997,52(4):374-381

在大量实测年径流量资料的基础上，分析了作为水文干旱定量指标负轮长的统计变化特性，并以哈尔滨和陕县为例，以随模拟途径探讨了严重干旱出现可能性的定量估计方法。结论是：－Ⅲ型分布可用来表示负轮长的统计特征；严重干旱出现可能性的定量估计，随机模途径最适当。  相似文献