布莱克（Blake）负向极性幕研究的新进展

本文概述了国内外布莱克负向极性幕的研究历史与现状，报导了许家窑旧石器遗址上更新统湖相剖面布容正向极性时（带）中负向极性段的位置、时间及剩磁特征。根据剖面上铀子系法测定的年代值和该负向的转换性质，笔者确认该负向极性段时间上对应于布莱克负向极性幕。     

巨大撞击对地球演化的系统灾变效应

综述了巨大地外物体撞击事件对地球产生的一系列剧烈灾变效应，包括撞击事件诱发或产生的各类地质作用变化、古气候波动、古生物灭绝和古地磁倒转等。同时指出，全面深入地研究巨大撞击的灾变效应对认识地球演化和发展具有重要意义。     

古地磁学在地磁场起源研究中的应用

地磁场起源及其倒转是地球科学的难题之一。究其原因一方面是由于无法直接观测地球内部发生的物理过程,另一方面是由于缺乏理论与实验相结合的综合研究。本文以磁流体力学为基础,将古地磁学与αω发电机理论结合在一起进行分析和研究。得出了如下新观点:(1)洛仑兹力在地核发电过程起负反馈作用;(2)较差旋转控制着地磁场西向漂移,(3)α作用使地磁极偏离地球自转轴     

An appraisal of the velocity-reversal hypothesis for stable pool-riffle sequences in the river severn,England

The ‘velocity-reversal hypothesis’ is the linchpin for a number of recent conceptual models pertaining to sediment sorting and the maintenance of pool-riffle sequences in gravel-bedded streams. The literature in support of the hypothesis together with published adverse criticism is reviewed. It is concluded that convincing evidence for the ubiquitous occurrence of such a reversal in a range of channel geometries is currently unavailable. Continuity considerations indicate that riffles need to be considerably wider than pools for a reversal in the mean velocity to occur under conditions of subcritical flow, high stage, and stable morphology. These observations are substantiated by a detailed study of the hydraulic geometry of stable pool-riffle sequences in the River Severn, England. Neither the sectionally-averaged velocity nor the near-bed shear velocity is sensibly greater in the pools than over the riffles during bankfull or near bankfull flow. Instead a tendency towards equalization of the values of average hydraulic variables is noted as discharge increases. A detailed investigation of the three-dimensional character of the flow is required to demonstrate whether the entrainment forces within pools can locally exceed those over neighbouring riffles. Unusual behaviour of the energy gradient over riffles during moderate discharges is related to backwater effects as mediated by the spacing of the riffles. The hydraulic data are used to comment on the stability of the test reaches in the context of the development of the River Severn in the vicinity of Shrewsbury.     

人工引雷上行正先导传播过程中爆发式磁场脉冲极性反转现象的观测与分析

为了进一步理解人工引雷上行正先导的传播过程及相关的爆发式电磁辐射脉冲,本文分析了2014年8月23日山东沾化人工触发闪电实验（SHATLE）中获得的三次上行正先导通道含有明显向下传播过程的个例。结果表明,在初始连续电流阶段观测到的爆发式磁场脉冲极性反转现象与正先导头部发展方向相对于观测位置投影方向的变化密切相关。因此可以推断,爆发式磁场脉冲是由正先导头部较小空间尺度放电过程辐射出的,就本文分析的个例而言,爆发式磁场脉冲辐射源的放电尺度约为2 m,放电强度的最大值达到2.49 kA。爆发式磁场脉冲的辐射机制不同于人工引雷先导始发阶段初始脉冲电流产生的磁场脉冲的辐射机制,可能与正先导通道头部的梯级形式发展过程相关。     

山东相态逆转降雪天气的特征与预报

采用高空和地面观测资料,对山东1999—2013年24次有相态逆转降雪过程的影响系统、出现时间、逆转前后的温度变化及各类系统逆转的天气形势特征进行了统计分析。结果表明：1）低槽冷锋、江淮气旋、黄河气旋和暖切变线可在山东产生降水相态逆转,而回流形势降雪不会产生逆转。2）山东降水相态逆转发生在11月—次年4月,以12月和1月居多,12月频率最高;有明显的日变化,14时前后最容易发生逆转,而23时—次日05时最少。3）雪转雨时最显著的特征为地面2 m气温升高,升温幅度多在1～2 ℃;850 hPa以下至地面的温度至少有1～2个层次升温。4）地面2 m气温对逆转的指示性最好,降雪时在0 ℃左右,略高于通常降雪阈值,最低为-1 ℃;其次为1 000 hPa,降雪时接近于0 ℃。5）对流层低层暖平流升温或温度日变化升温导致雪转雨,温度平流弱时温度日变化起主要作用。各类天气系统的逆转范围、时段等有明显差异。因此,对于降雪阈值附近的相态预报,需综合考虑低层温度平流和日变化两个因素,重点关注地面2 m气温能否升温,午后为关键时段。     

The brightness reversal of submarine sand waves in “HJ-1A/B” CCD sun glitter images

The brightness reversal of submarine sand waves appearing in the small satellite constellation for environment and disaster monitoring and forecasting("HJ-1A/B") CCD sun glitter images can affect the observation and depth inversion of sand wave topography. The simulations of the normalized sun glitter radiance on the submarine sand waves confirm that the reversal would happen at a specific sensor viewing angle, defined as the critical angle. The difference between the calculated critical angle position and the reversal position in the image is about 1, which is excellent in agreement. Both the simulation and actual image show that sand wave crests would be indistinct at the reversal position, which may cause problems when using these sun glitter images to analyze spatial characteristics and migration of sand waves. When using the sun glitter image to obtain the depth inversion, one should take the advantage of image properties of sand waves and choose the location in between the reversal position and the brightest position. It is also necessary to pay attention to the brightness reversal when using "HJ-1A/B" CCD images to analyze other oceanic features, such as internal waves, oil slicks, eddies, and ship wakes.