液氮消冷雾微结构的演变分析

液氮已广泛用于外场的人工增雨和消雾，是“十五”人工影响天气攻关研究和推荐的催化剂之一；其优势在于价廉，对环境无污染，资源丰富，-8℃以上成冰率高于AgI。文章介绍用液氮在首都机场的消雾试验，讨论和分析了消雾前后雾微结构的演变。对地跨北京14个区县，持续48h，能见度最低时达20～30m的气团平流雾连续播撒液氮，35min后下风方4．8km的测立占出现冰雪晶，形状以柱状为主，平均浓度为0．35个／cm^3。冰雪晶的出现破坏了雾的胶性稳定性，能见度很快得以改善，水平能见度增加到300～600m。     

集合预报研究现状与展望

本文系统地论述了集合预报的概念、分类以及国外内的研究现状,在国外的研究现状中重点介绍了目前国际上最先进、最具代表性的两种方法,奇异向量法和增长模繁殖法。国内则介绍了在该方面的最新进展,包括我实验室所做的工作。最后阐述了集合预报的可能发展方向和应用前景。     

Current structure and its variation in the equatorial area of the western north Pacific Ocean

Based on the current measurement data from the R/V Ryofu Maru of JMA in the equatorial area along 137°E (1972–83) and 155°E (1972–79) the structures of the zonal velocity of the Equatorial Undercurrent (EUC) and the North Equatorial Countercurrent (NECC) and their variations are systematically analyzed in detail. At 155°E, the current at the equator and 100–300 m depth was a typical eastward EUC, it intensified in 1973–75, i.e., in the non-El Niño period. While the corresponding current at 137°E was mostly westward, and the origin of the EUC shifted to north of the equator around 0.5–1.5°N owing to the influence of the New Guinea Coast. The EUC origin disappeared in early July, 1982. Comparing with the EUC disappearance at 159°W, the average speed of an eastward travelling wave would be～1.1m/s. The velocity core of the NECC at 137°E generally shifted northward in winter and southward in summer, and was stronger in summer and weaker in winter. The fluctuations of the NECC were closely related to those of the wind stress curl over the region 2–10°N, 160°E–150°W.     

A note on the deep circulation in the area east of Taiwan and the Philippines

The deep water (1000–3000 m) circulation in the area east of Taiwan and the Philippines has been little studied. Moriyasu (1972) and Reid (1981) discussed the 3000 db surface (3000/1200 db) and 2000 db surface (2000/3500 db) circulations of the Philippine Sea Basin, respectively. They both showed that there may be a northward current close to the western margin of the Sea Basin. Recent analyses of two sets of deep sea hydrographic data yielded quite different results, i. e., at deep waters in the area east of Taiwan and the Philippines southward countercurrents flow under the upper northward currents. The possible causative mechanism of these southward deep countercurrents is the blocking effects of the submarine ridge east of Suao and of the Ryukyu Islands Shelf on the northward flowing upper currents. The above-mentioned preliminary deductions were wholely based on consideration of the relative geostrophic current and calculation, though the reference surface (3500 db) was very deep. It is suggested that direct measurements of the deep currents in the study area are needed to verify these results. Contribution No. 1750 from the Institute of Oceanology, Academia Sinica. This paper was presented at the PRC/USA Symposium on Western Pacific Air-Sea Interaction (Nov., 1988, Beijing). This project was supported by the National Natural Science Foundation of China.     

Spatial weighting functions: transient hydraulic tests and heterogeneous media

To improve understanding of property measurements in heterogeneous media, an energy-based weighting function concept is developed. In (assumed) homogeneous media, the instrument spatial weighting function (ISWF) depends only on the energy dissipation distribution set up by the measurement procedure and it reduces to simply inverse sample volume (uniform weighting) for 1-D parallel flow case (ideal permeameter). For 1-D transient flow in homogeneous media, such as with slug tests, the ISWF varies with position and time, with 95% of the total weighting contained within 115 well radii, even late in the test. In the heterogeneous case, the determination of the ISWF is connected to the problem of determining an equivalent hydraulic conductivity (K), where the criterion for equivalence is based on equal energy dissipation rate rather than equal volume discharge. The discharge-based equivalent K (K(E)) and the energy-based equivalent K in heterogeneous media (K(eh)) are not equal in general, with K(eh) typically above the nodal arithmetic mean K. The possibly more fundamental problem is that as one makes K measurements in heterogeneous media at different locations or on different cores of heterogeneous materials, the ISWF will be heterogeneity dependent, implying that the averaging process resulting in the equivalent K value also varies with position. If the testing procedure is transient, then the averaging process varies with time. This suggests a fundamental ambiguity in the interpretation of hydraulic conductivity measurements in heterogeneous media that may impact how we approach modeling and prediction in a practical sense (Molz 2003). Further research is suggested.     

春季格陵兰海冰与夏季中国气温和降水的关系

采有英国Hadley中心的GISST海冰面积资料，NCFP／NCAR再分析资料以及中国160站气温和降水资料，分析了春季格陵兰海冰面积与夏季中国区域气温和降水的关系。初步研究表明，春季格陵兰海冰面积变化和随后夏季我国黄河长江中下游之间地区气温以及8月份华北和西南地区降水呈明显正相关，而和6月黄河中上游地区降水则具有明显的负相关。同时，春季格陵兰海冰异常时期对应着北半球大气环流的明显主为化，表明海冰与我国气温及降水之间的联系具有一定的环流背景。     

Deep process of the collision and deformation on the northern margin of the Tibetan Plateau: Revelation from investigation of the deep seismic profiles

The seismic investigation achievements from three kinds of methods have revealed the lithospheric structure and the deep process of deformation caused by collision. It is found that convergent collision and deep subduction of the continental lithosphere are in progress along the northern margin of the Tibetan Plateau. The deep process of due collision and deformation is different from that of oblique collision. It is revealed in the study that the deep process of the collision and deformation on the northern margin is different from that on the southern margin of the Tibetan Plateau.     

Tectonic-climatic events in eastern Qilian Mountains over the past 0.83 Ma

The eastern part of Qilian Mountains experienced strong tectonic uplift during the late Quaternary, and climate record there was influenced by Tibetan Plateau to some extent. Based on studies on the fluvial terrace series and eolian loess deposition, we find that the tectonic uplifts of the Tibetan Plateau had coupled with climatic changes in our studied region and others since the mid-Pleistocene. The uplift that occurred at 0.83 Ma corresponded to significant desert expansion in L6 and periodic variation since MIS16, while the 0.14Ma one to the further drying in northwest China. Those coupled events may indicate that tectonic uplift drove climatic changes, and the Tibetan Plateau has important impacts on East Asian Monsoon system.     

广西柳州白莲洞遗址的铀系年龄

因涵盖新—旧石器过渡、出土人类化石及别具一格的石制品 ,广西柳州白莲洞遗址对古人类和石器文化的研究具有重要意义。新生碳酸盐岩铀系测年的结果表明 :该遗址新—旧石器间的过渡期不超过 3ka± ,短于基于钙板 1 4 C测年得出的 6 ka± ;西 6层钙板和石笋的 2 3 0 Th年龄为 16 0 ka± ,西 7层人牙化石的年代应大于此值 ;“白莲洞式”石片打制法呈清晰的演化脉络 ,时间跨度至少为 15 0 ka。邻近的柳江人地点和土博前洞铀系测年结果与本文一致。这些地点年代位置的大幅度前移 ,是我国晚更新世人类遗址已有年代框架被总体压缩的例证。具现代解剖特征的智人在中国出现的年代很可能比原认为的早得多