空间分辨率对中国夏季降水时空演变特征的影响

本文使用1979—2021年国家气候中心160站(R₁₆₀)和国家级地面气象观测站2 314站(R₂₃₁₄)逐月降水观测资料,利用EOF (Empirical Orthogonal Function)分解和相关分析等方法,研究两类资料夏季降水时空变化特征及其与海气因素之间物理联系的表征水平差异,并分析了差异的可能原因。结果表明,R₁₆₀在我国西北、青藏高原等地区站点极为稀疏,导致其各EOF模态对上述地区降水的时空变化特征描述失真,中东部地区偏低的空间分辨率会使局地强降水的变化特征信号损失,造成降水的年际变率降低。而R₂₃₁₄主模态能够更为真实地反映我国降水的时空演变特征,特别是在极端降水频发的江淮地区以及降水受局地地形影响较大的山区,其EOF主模态的空间分布和时间系数演变与ENSO (El Niño-Southern Oscillation)、西太平洋副热带高压、青藏高原雪盖等气候强迫信号之间的相关性更为显著。     

新疆北部大地构造研究中几个问题的评述——兼论地质图在区域构造研究中的重要意义

地质图是区域地质和大地构造研究的重要基础资料,认真研读地质图是大地构造学研究的重要途径。以新疆北部几个重要构造带为例,展示了地质图的分析、研读在大地构造研究中的重要意义。基于地质图分析并结合最新的研究资料,认为东准噶尔卡拉麦里造山带的碰撞时限不晚于早石炭世(370~340Ma);西准噶尔达拉布特构造带形成于石炭纪晚期,该带不具有板块边界或者俯冲-缝合带的属性;以巴音沟蛇绿岩带为代表的北天山洋盆的缝合时限在晚石炭世(325~316Ma)。由此推断,新疆北部地区洋盆俯冲和地体拼贴碰撞造山过程应该在晚石炭世之前完成。     

三维F－K域DMO方法及应用效果

在常速情况下,从三维时距方程出发,通过倾角代换,将三维倾角时差分裂为两个正交方向上的二维倾角时差,然后在这两个正交方向上分别做一次二维倾角时差校正,便可达到三维倾角时差校正的目的．应用实例表明这种三维ＤＭＯ分裂方法是切实有效的．     

高分辨率地震成像研究--21世纪地震学发展的一个重要趋势

随着宽频带地震观测技术的不断发展,全球及区域数字地震观测台网的密度正在不断加大,用于流动地震观测的宽频带地震仪的数量将继续迅速增加。与此同时,宽频带数字地震观测资料的积累速率按指数增长,这意味着震源波裂过程及地球内部结构的高分辨率地震成像研究将成为２１世纪地震学发展的重要趋势。地震学与地球动力学研究的关系将日趋紧密,宽频带流动地震观测的作用和重要性必将与日俱增。     

Effect of urbanization on runoff characteristics of the On-Cheon Stream watershed in Pusan,Korea

This study investigated the effect of urbanization on runoff from the On-Cheon Stream watershed in Pusan, Korea. This watershed has been experiencing considerable urbanization since the 1960s. There are two gauging stations in the watershed. For one of the stations there are recent flow data and for the other flow data were observed in the past. A linear reservoir model was chosen and runoff was analysed for several flood events. The linear reservoir model has been found to generate flood hydrographs accurately for both gauging stations, and its applicability to the study area has also been established. Using two methods of computing effective rainfall or rainfall excess (ϕ-index and constant percentage method), the results of runoff analyses were investigated. The ϕ-index method yielded better results than the constant percentage method. A comparison of hydrographs observed in the past with the simulation results at the Ie-Sup bridge site revealed that the peak discharge increased and the mean lag time of the study area decreased owing to urbanization over the past two decades. It is also possible to evaluate the effect of urbanization quantitatively. © 1998 John Wiley & Sons, Ltd.     

Dehydration melting of solid amphibolite at 2.0 GPa: Effects of time and temperature

The dehydration melting of the natural rock at high pressure is important to investigating the magma formation in the earth’s interior. Since the 1970s, a lot of geological scientists have paid more atten- tion to the dehydration melting of the natural rock[1―5]. Previous experiments of dehydration melting and observations of fieldwork argued that the dehy- dration melting of the rock was probably the most important fashion for the melting of the lower crust rock[6―12]. The genesis of most …     

Geochemical and hydrodynamic constraints on the distribution of trace metal concentrations in the lagoon of Nouméa, New Caledonia

Seawater samples were collected in the lagoon of Nouméa (southwest New Caledonia) along two transects from eutrophic coastal bays to the oligotrophic barrier reef. Land-based emissions to the lagoon were measured with dissolved and particulate concentrations of chromium (Cr) and nickel (Ni), used as tracers of both terrigenous and industrial (Ni ore treatment) activities, as well as dissolved and particulate concentrations of zinc (Zn), used as a tracer of urban effluents. The spatial variability of metal concentrations was related to geochemical and hydrodynamic conditions, i.e., respectively: (1) natural and anthropogenic emission sources, and chemical processes occurring in the water column; and (2) water residence times. The parameter used to describe the residence time of water masses was the local e-flushing time, i.e. the time required for a tracer mass contained within a given station to be reduced by a factor 1/e. High metal concentrations were found in coastal areas (up to 9000 ng dissolved Ni L⁻¹), and steeply decreased with distance from the coast (down to 101 ng dissolved Ni L⁻¹ near the barrier reef) to reach levels similar to those found in remote Pacific waters, suggesting a rapid renewal of waters close to the barrier. Distributions of metals in the lagoon are controlled upstream by land-based emission sources and later chemical processes. Then hydrodynamics constrain metal distributions, as shown by the observed relationship between local e-flushing times and the spatial variability of metal concentrations. In addition, a change in the direction of prevailing winds yielded a decrease of dissolved metal concentrations at the same site by a factor of 2.5 (Cr and Ni) and 2.9 (Zn). It is suggested that the residence time is a key parameter in the control of elemental concentrations in the lagoon waters, as much as land-based emission sources.     

时差对海洋磁力测量地磁日变改正的影响分析

为研究时差对磁测的影响,基于站间同步地磁日变曲线的特征,尝试采用同步比对法和相关分析法计算两站的时差.结论表明:同步比对法和相关分析法能反映站间真实的时差,当测区范围较小时(至少是在本文实例的两个地磁日变站之间),时差对地磁日变改正的影响很小,海洋磁力测量地磁日变改正时可以忽略其影响.