1991年江淮特大暴雨与东亚大气低频振荡

本文分析了１９９１年江淮特大暴雨期间东亚大气低频振荡活动。从低频振荡特征看，江淮雨量和东亚风场中低频振荡现象是普遍存在的，风场的振荡周期具有显著的地域和频域分布特征。从低频波的传播看，这一梅雨过程的两个异常阶段（５月下半月和７月上半月），东亚风场低频波的水平传播方向发生了显著的变化。分析指出，低纬地区低频波虽有不同传播方向，但都将暖湿空气以低频形式输送到江淮以南，它与北侧的低频冷空气在江淮地区相互作用，从而导致该地区以低频形式出现的３场特大暴雨。     

多遥感卫星接收系统和其数据接收

该文叙述了单遥感卫星接收系统升级改造为多卫星接收系统所进行的研制工作。包括天线跟踪系统与高频信道的改造，卫星捕获软件的开发，中频接收解调设备的研制以及系统的总装调试等。     

青藏高原感热加热异常与夏季低频环流的数值研究

使用科学院大气物理研究所两层大气环流模式，就青藏高原地表感热通量异常减少对夏季东半球大气环流及亚洲季风低频变化的影响进行了数值试验研究。结果表明：高原地区感热通量异常减少时，南海及西太平洋地区低频振荡方差百分率增大；高原感热异常加热对东亚和印度季风子系统具有不同的影响，季风区低频扰动的位相，中高纬低频扰动的结构，强度和经向传播速度都发生改变，ＥＡＰ波列变得更为清楚典型，大圆上的低频涡旋一直传播到我     

Hydrological impacts of flow regulation associated with the Upper Nepean water supply scheme,NSW

The upper Nepean River has been progressively regulated for water supply to Sydney and Wollongong since 1886 by the Upper Nepean Water Supply Scheme which consists of four large dams, two small dams and two diversion weirs. Secular rainfall changes produced periods of high rainfall and large floods (flood‐dominated regimes) between 1857 and 1900 and 1947 and the present, and an intervening period (1901–46) of low rainfall and small floods (drought‐dominated regime). Upstream impoundment and flow regulation significantly reduced flood magnitudes for most return periods during both types of flood regimes. The probability distribution of mean daily flows was also changed significantly by flow regulation such that during the drought‐dominated regime, the high and low frequency flows were reduced substantially but the moderate frequency flows were increased due to dam releases; the change from a regulated drought‐dominated regime to a regulated flood‐ dominated regime resulted in a substantial increase in discharge for most durations; and increased water diversions to Wollongong during the current flood‐dominated regime produced a marked downward shift in the whole flow duration curve. Nepean Dam reduced downstream suspended sediment yields by two orders of magnitude because it traps in excess of 99 per cent of the inflowing suspended sediment load. Streamflow releases are urgently required from the two diversion weirs to improve downstream water quality and to ensure the viability of the resident ‘potentially threatened’ eastern Macquarie perch (Macquaria nov. sp.).     

NIM-Ⅱ型可移激光绝对重力仪

中国第二代可移激光绝对重力仪（NIM-Ⅱ型）的实验装置于1985年研制成功。本文详细论述了仪器的多位置法原理及仪器结构;具体分析说明了仪器的光学系统,电子精密测时系统,数据处理系统;研究了一种处理地面微震干扰的新方法。参加1985年在法国巴黎举行的第二次国际绝对重力仪比对结果表明,该装置的测量结果不确定度为1.4x10^-7m/s²。国际比对后,仪器又做了进一步改进。经国内大面积测量应用的结果表明,该装置的不确定度可达1×10^-7m/s²。     

云南及其邻近地区地震活动的模式识别

本文用模式识别方法(CORA—3修改方法)研究了云南及其邻近地区大地震的发生时间与中强地震活动特性的关系。结果表明(不分子集):M≥7.0级大震前1—2年内,5—5.9级地震频度有明显增强。前1年6—6.9级地震相对减弱,前2—4年内6—6.9级地震可增至一定水平。对于CORA—3修改算法在采用“CLUSTERS”算法和不用“CLUSTERS”算法所得识别分类结果基本一致。FH(future history test)试验表明,用1930—1986年为学习时段,1969—1986年为预测时段。得到D类识别率为0.6,N类误识率为0.38。     

Scaling of peak ground motions from digital recordings of small earthquakes at Campi Flegrei,southern Italy

The dependence of peak ground acceleration and velocity on seismic moment is studied for a set of small earthquakes (0.7<M _L<3.2) recorded digitally at distances of a few km in the Campi Flegrei volcanic area near Naples, Italy, during the ground uplift episode of 1982–1984. Numerical simulations, using the -square spectral model with constant stress drop and ane ^–kf high frequency decay, fit well both the velocity and acceleration data for an averagek=0.015. The observed ground motions in the 1–24 Hz frequency band appear to consist of radiation from simple sources modified only slightly by attenuation effects. Moreover, the scaling of peak values agrees closely with those determined in nonvolcanic areas, once the difference in stress drop is taken into account.     

Unbiased estimation of flood risk with the GEV distribution

Conventional flood frequency analysis is concerned with providing an unbiased estimate of the magnitude of the design flow exceeded with the probabilityp, but sampling uncertainties imply that such estimates will, on average, be exceeded more frequently. An alternative approach is therefore, to derive an estimator which gives an unbiased estimate of flow risk: the difference between the two magnitudes reflects uncertainties in parameter estimation. An empirical procedure has been developed to estimate the mean true exceedance probabilities of conventional estimates made using a GEV distribution fitted by probability weighted moments, and adjustment factors have been determined to enable the estimation of flood magnitudes exceeded with, on average, the desired probability.     

频率域中有限元素法的探讨

本文指出了用拉普拉斯变换处理有限元方程和用富里叶变换所得到的结果是等价的。从物理方面讨论了频率域有限元的局限性。