Global spectra of energy and enstrophy and their fluxes during July 1979

Transient and stationary spectra of kinetic energy (KE), available potential energy (APE) and enstrophy (EN), and their spectral fluxes as a function of the two-dimensional wavenumbern were computed for July 1979. Triangular truncation at zonal wavenumber 42 was used for computation. The slopes of various spectra in the wavenumber range 14≤n≤25 were obtained by fitting a straight line in log-log scale by the least square method. The transientKE, APE andEN spectra in the lower (upper) troposphere had slopes −2·21 (−2·30), −2·65 (−2·64) and −0·36 (−0·46), respectively. The effect of stationary and divergent motion on the slope values was investigated. The possible correlation between the slope and percentage of transient component in the combined energy and enstrophy was examined to identify the transient motion of the atmosphere with the two-dimensional homogeneous isotropic turbulence. The vertically averaged slope of kinetic energy and enstrophy in the lower (upper) troposphere was close to the value at 700 (200) hPa level. The spectral fluxes of kinetic energy and enstrophy in the wavenumber range 14≤n≤25 satisfied, to a very rough approximation, the criteria of inertial subrange. The stationary fluxes were small. The estimated stationary-transient component of flux was larger, comparable and less than the corresponding transient flux of APE, KE and EN. Representative levels for computation of energy and enstrophy spectra and their fluxes in the lower and upper troposphere were identified.     

Simulation of flow over pool-riffle topography: A consideration of the velocity reversal hypothesis

Computer flow simulations using the HEC-2 step-backwater routine are used to demonstrate the effect of systematically varying river channel width, riffle spacing and channel roughness on the shear velocity, section-mean velocity and energy slope in fixed-bed pool-riffle sequences. Initial scaling is obtained by utilizing published information on hydraulic parameters within reaches of the River Severn. Subsequently this restriction is relaxed and the effect of varying parameter combinations within realistic limits is explored. The purpose of this exercise is to isolate those scenarios which may preclude or promote the occurrence of a competence ‘reversal’, such that pools scour at high flow whilst deposition occurs on riffles. It is concluded that rivers in which pools are hydraulically rougher than riffles are likely to demonstrate a competence reversal. For prescribed conditions, the critical discharge at which a reversal occurs is a negative function of riffle spacing and riffle width relative to pool width. Downstream variation in hydraulic roughness also has implications for the phase relationship of shear velocity maxima and minima in relation to the extremes in pool-riffle topography.     

TRAJECTORY DIAGNOSIS OF AIR PARCELS IN HIGH-AND LOW-LEVEL JETS FOR A HEAVY RAINFALL CASE DURING MEIYU SEASON OF 1991

Trajectory diagnostic methods were used to analyze air parcels of high-and low-level jets during the heavy rainfall of 4-6 July 1991.It is found that air parcels above rainfall area travelled from the entrance of the high-level jet,passing through the jet center and reached the exit region.Upper tropospheric divergence over rainfall area resulted from decelerative motion of the jet flow.Warm and moist southwest flow converged and ascended ahead of the low-level jet.The decreasing of low-level pressure as a result of high-level divergence that caused the low-level jet became unexpectedly strong.     

北上热带气旋发展与不发展的对比分析

重点分析了一个北上热带气旋（８５０９号台风）变性发展过程中扰动能和扰动有效有效位能的收支平衡关系及其与中纬地区高空环境场、Ｑ矢量散度、旋度特征和锋生锋消现象的联系，并和与此台风前期路径及强度相似、但进入西风带后很快消失了的８４０６号台风的诊断结是要 进行了对比。结果表明：有利的大尺度环境是台风变性发展的主要因子和先决条件，斜压过程是否能有效和大量地制造扰动动能以抵消台风北上过程中的能量耗散是其能否     

地幔滞弹性对Chandler摆动的影响

基于简正模扰动理论和勒夫数扰动方法,采用Zschau 的地幔流变模型,在假设Chandler摆动的能量全部耗散于地幔滞弹性摩擦的条件下,导出Chandler 摆动Q(Q_w)的理论值.还考虑了滞弹地球的平衡极潮对摆动的影响,所得结果与绝大部分天文实测值非常一致.分析表明.平衡部分的影响大,地幔滞弹性很可能是Chandler 摆动最主要的能量耗散源,Q_w 的理论值约为71.还推算了吸收带模型参数α,研究了该模型的适用性,并讨论了Q_w 与地幔Q(Q_m)的关系.     

鲜水河断裂带多断层相互作用的流变断裂力学分析

本文研究了流变介质内多断层的相互影响,通过对鲜水河断裂带的分析,对该断裂带提出一个不共线三断层的断裂力学模型.把介质考虑成流变的,用有限元法结合解析方法求解了流变断裂力学问题的应力、应变及能量场的时空变化.结果表明,多断层的力学场与单一断层的力学场相差甚远,在断层间形成了影响区.在影响区内应力集中,梯度大,分布复杂,应变能在影响区内形成较大范围集中.应变能等值线在孕震期间从影响区向外扩张,能量从外围流向断层区,流动在时空上都是不均匀的,孕育初期增加速率大,后期渐渐平缓.流向影响区的能量比其周围区域大,形成很大梯度.并讨论了地震前兆的某些特征.根据本文的结果,认为在道孚-乾宁-带发生地震的可能性较大.     

中国沿海城市的气块后向轨迹分析

该文讨论了大连、青岛、上海、福州、厦门和广州６个沿海城市的气块长距离后向输送轨迹。输送层假设在１５００ｍ上，计算了１９８５年１、４、７、１０月份的轨迹，轨迹分析得出：（１）气块后向轨迹与天气形势和季节有关，且南北方有差异；（２）北方沿海城市的７２小时气块后向轨迹输送距离要比南方沿海城市远些。     

磁层系统的能量输入、输出与日地耦合

用１９７８年和１９８２年３６个磁暴期间的太阳风、行星际磁场（ＩＭＦ）和地磁资料，分析和检验已有的两类太阳风－磁层能量耦合函数．结果表明：Ａｋａｓｏｆｕ提出的耦合函数ε能大致地预报亚暴和磁暴的发生。ε开始起重要作用时即出现亚暴；电离层能耗达到饱和值是发生磁暴的标志。ε与磁层体系能耗之间有接近于对数量的线性关系．用１９７８－１９８６年的资料，分析环电流和极光区电离层能耗在１２１个太阳自转周内的分布表明，日面上可能存在相对持久的活动区域     

21世纪能源与环境的前沿问题——天然气水合物

天然气水合物资源极为丰富。据国外专家估算，水合物中的天然气总资源超过了包括煤炭、石油与常规天然气在内的所有已知可燃矿产的储量。天然气水合物层是油气聚集的极好盖层，可以作为勘探油气藏的标志。天然气水合物还是影响全球气候变化的重要温室气体之一的甲烷的重要源和汇。因此，进行天然气水合物研究对开拓２１世纪能源、完善油气成藏理论、解决天然气工业生产和输送过程的管进堵塞问题，以及探讨其与全球气候变化的关系问题均有重大意义。目前应开展的研究内容与重点课题包括：天然气水合物的成因机制与油气成藏演化规律；分布规律及有利蕴藏地区；物化特性及其生成与消除的方法；天然气水合物与全球气候变化的关系等。