太阳大气中磁重联的MHD数值模拟

回顾了近３０年太阳大气中磁重联过程的ＭＨＤ数值模拟工作取得的进展。着重描述了在验证理论模型,解释观测现象,以及研究各种因素对重联的影响三个方面的成果,如快速磁重联,太阳耀斑机制及色球,日冕中的各种爆发现象等。指出了在数值模拟中应注意的几个问题,并对该领域今后的发展作了简要的展望。     

基于分等定级的海岸带资源价值评估方法研究

海岸带资源价值评估是对海岸带资源进行资产化管理和实施有偿使用制度的前提和关键.海岸带资源的价值受多种因素的影响,不同地区的同一种海岸带资源或同一地区的不同种海岸带资源的质量都有所差异.因此,海岸带资源价值评估应在对其分等定级的基础上进行,这样才能体现海岸带资源质量的优劣和资本收益的差异.在分析海岸带资源价值影响因素的基础上,针对目前海岸带资源价值评估方法的不足,根据生产力理论、区位理论和地租理论提出了基于分等定级的海岸带资源价值评估方法体系,以推进我国海岸带资源资产化管理和有偿使用制度的实施,保证海岸带资源的可持续利用.     

基于CA模型的3维虚拟城市构建方法研究

结合城市元胞自动机(CA)方法和虚拟现实(VR)技术,构建一个基于元胞的3维虚拟城市.首先建立基于元胞实体数据结构的城市CA模型,用以表示3维虚拟城市中建筑物的平面分布状态.通过CA模型生成一组城市建筑物的时空分布数据.然后利用DEM和DOM数据生成一个真实的3维地形,建立了不同种类的3维建筑模型库.最后通过程序调入城市3维建筑模型,根据元胞实体属性将模型布设于3维地形的相应位置,生成3维虚拟城市.

Abstract：

This paper unified the urban cellular automata method and the virtual reality technology to construct a three-dimension (3D) virtual city which was based on automata. First, constructing an urban CA model that is based on the data structure of cellular entities can present the plane distribution state of the building in the 3D virtual city. The CA model was used to compute a group of temporal layout data of buildings in the virtual city,Then,DEM and DOM data were used to generate real three-dimensional terrain and produce different type library about 3D building model. Finally, The program was used to load and lay the 3D buildings to the corresponding position in the 3D virtual terrain to obtain a 3D virtual city, according to the cellular entity attribute.     

Late Cretaceous Foraminiferal Faunas from the Saiqu "mélange" in Southern Tibet

As one of the mélanges in the southern side of the Yarlung-Zangbo suture zone, the Saiqu mélange in southern Tibet is important for understanding the evolution of the Neo-Tethys ocean. The age of the Saiqu mélange, however, has been debated due to the lack of reliable fossil evidence in matrix strata. Based on lithological similarities with platform strata in southern Tibet and limited fossils from exotic blocks, previous studies variously ascribed the Saiqu mélange to be Triassic in general, Late Triassic, or Late Cretaceous. Here we reported planktonic foraminiferal faunas from the matrix strata of the Saiqu mélange. The new fossils yield a Late Cretaceous age, which is so far the best age constraint for the mélange. Regional stratigraphic correlation indicates that the Cretaceous Oceanic Red Beds (CORBs) in Saiqu may be time equivalent to the CORBs of the Zongzhuo Formation in neighboring regions. Thus the Saiqu mélange should be correlated to the Upper Cretaceous Zongzhuo Formation rather than the Triassic Xiukang Group, as previously suggested.     

关于鄂尔多斯盆地白垩系地下水分水岭的探讨

通过研究鄂尔多斯白垩系盆地地下水环境同位素 (18O、D、T), 认为鄂尔多斯盆地白垩系地下水分水岭位于陕北, 大致呈东西向分布的白于山一带。      

海域分等与海域使用基准价评估研究——以广东省沿海地市为例

海域使用基准价是海域使用金征收标准科学制定的基础.以广东省各地级市海域作为研究对象,以实例方式详细阐述了海域分等的工作程序、技术方法,在借鉴土地评估的基本理论和方法的基础上,从海域的实际情况出发,探讨了海域使用基准价的组成、计算思路和方法,初步建立了不同海域类型的海域使用基准价评估方法体系,这对完善海域分等定级与海域基准价评估理论、科学制定海域使用金征收标准具有重要意义.     

Moisture origin and stable isotope characteristics of precipitation in southeast Siberia

The paper presents oxygen and hydrogen isotopes of 284 precipitation event samples systematically collected in Irkutsk, in the Baikal region (southeast Siberia), between June 2011 and April 2017. This is the first high-resolution dataset of stable isotopes of precipitation from this poorly studied region of continental Asia, which has a high potential for isotope-based palaeoclimate research. The dataset revealed distinct seasonal variations: relatively high δ¹⁸O (up to −4‰) and δD (up to −40‰) values characterize summer air masses, and lighter isotope composition (−41‰ for δ¹⁸O and −322‰ for δD) is characteristic of winter precipitation. Our results show that air temperature mainly affects the isotope composition of precipitation, and no significant correlations were obtained for precipitation amount and relative humidity. A new temperature dependence was established for weighted mean monthly precipitation: +0.50‰/°C (r² = 0.83; p <.01; n = 55) for δ¹⁸O and +3.8‰/°C (r² = 0.83, p < 0.01; n = 55) for δD. Secondary fractionation processes (e.g., contribution of recycled moisture) were identified mainly in summer from low d excess. Backward trajectories assessed with the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model indicate that precipitation with the lowest mean δ¹⁸O and δD values reaches Irkutsk in winter related to moisture transport from the Arctic. Precipitation originating from the west/southwest with the heaviest mean isotope composition reaches Irkutsk in summer, thus representing moisture transport across Eurasia. Generally, moisture transport from the west, that is, the Atlantic Ocean predominates throughout the year. A comparison of our new isotope dataset with simulation results using the European Centre/Hamburg version 5 (ECHAM5)-wiso climate model reveals a good agreement of variations in δ¹⁸O (r² = 0.87; p <.01; n = 55) and air temperature (r² = 0.99; p <.01; n = 71). However, the ECHAM5-wiso model fails to capture observed variations in d excess (r² = 0.14; p < 0.01; n = 55). This disagreement can be partly explained by a model deficit of capturing regional hydrological processes associated with secondary moisture supply in summer.     

What do Δ14C changes across the Gerzensee oscillation/GI‐1b event imply for deglacial oscillations?

High‐resolution studies were performed on late‐glacial sediments from a small lake in western Denmark with respect to lithology, geochemistry, stable isotopes, pollen stratigraphy and radiocarbon dating on terrestrial macrofossils. One purpose was to detect the so‐called Gerzensee oscillation, or the GI‐1b event, in the later part of the Allerød warm period, and to describe the environmental impact of this short cooling. The other aim was to test the hypothesis that considerable Δ¹⁴C changes occur over this time, which can be related to ocean ventilation/thermohaline circulation changes. We find that the GI‐1b event had a major impact on both terrestrial and limnic ecosystems: large vegetation changes, increased soil erosion and lowered aquatic production. By correlations to events in the GRIP ice‐core and ¹⁴C patterns in the Cariaco basin we also transformed our ¹⁴C dated record into calendar years to calculate Δ¹⁴C values. The ¹⁴C dates show that the GI‐1b event both preceded, and was part of, the 11 400–11 300 ¹⁴C yr BP radiocarbon plateau, and was followed by the 11 000–10 900 ¹⁴C yr BP plateau; thus the later part of the event coincides with a distinct age decline. This delayed age drop (Δ¹⁴C rise) in relation to the hypothetical triggering mechanism behind the event, decreased ocean ventilation, could be explained by redeposited macrofossils at the onset of GI‐1b. This phenomenon, also seen at the onset of Younger Dryas, may also reflect increased soil erosion and redeposition at the start of cold periods. The independent Cariaco Basin record, however, implies that the very end of the cool GI‐1b event is related to a distinct rise in Δ¹⁴C. Likewise, the ¹⁰Be record from GISP2 shows a distinct rise in the middle of the event, precluding decreased solar forcing as the trigger of the climate event, but making it likely that high cosmic ray flux (low solar activity) may be the cause of the rising atmospheric ¹⁴C content. We thus conclude that the Δ¹⁴C changes over the Gerzensee oscillation (GI‐1b), being one of several coolings during the Last Termination, does not seem to be related to ocean ventilation changes. The reason behind this lack of coincidence between rising Δ¹⁴C and a fairly distinct Northern Hemisphere cooling may be due to the fact that the oceanic changes during some of these coolings are too subtle to give an atmospheric ¹⁴C imprint, or that an anti‐phase relationship between the two hemispheres blurs the Δ¹⁴C signal, or, finally, that a partly unknown mechanism may lie behind such coolings. Copyright © 2000 John Wiley & Sons, Ltd.     

A multilayer study of pCO2 in the surface waters of the Yellow and South China Seas in spring and the sea-air carbon dioxide flux

A multilayer study of pCO₂ for the Yellow and South China Seas in the surface waters was conducted based on data from four cruises sponsored by the China SOLAS Project in 2005 and 2006, including data for the surface microlayer (SML), subsurface layer (SSL) and surface layer (SL). The carbon fluxes across the air-sea interface were calculated. The results showed that the pCO₂ values in the surface waters of the study area decreased in the following order: pCO_{2 SML} > pCO_{2 SSL} > pCO_{2 SL}. The highest values were found in March for all SML, SSL and SL, followed by those in April, and the lowest were in May. The pCO₂ values had a significant positive correlation with temperature or salinity. While there was no relationship between pCO₂ and longitude, there was a significant negative correlation between it and latitude, i.e., ‘high latitude low pCO₂’. By using four calculation models, the carbon dioxide fluxes ( ) in spring in the Yellow and South China Seas, which were found to act as a ‘sink’ of atmospheric CO₂, were preliminarily estimated on the basis of the pCO₂ data in the SML to be −7.00×10⁶t C and −22.35×10⁶t C, respectively. It is suggested that the calculated on the basis of pCO₂ data in the SML is more reliable than that calculated on the basis of those in the SL.     

Remote sensing application to estimate the volume of water in the form of snow on Mount Lebanon / Application de la télédétection à l’estimation du volume d’eau sous forme de neige sur le Mont Liban

Abstract

Abstract At least one-quarter of the Lebanese terrain is covered by snow annually, thus contributing integrally to feeding surface and subsurface water resources. However, only limited estimates of snow cover have been carried out and applied locally. The use of remote sensing has enhanced significantly the delineation of snow cover over the mountains. Several satellite images and sensors are used in this respect. In this study, SPOT-4 (1-km resolution) satellite images are used. They have the capability to acquire consecutive images every 10 days, thus monitoring the dynamic change of snow and its maximum coverage could be achieved. This was applied to Mount Lebanon for the years 2001–2002. The areas covered by snow were delineated, and then manipulated with the slope angle and altitudes in order to classify five major zones of snowmelt potential. The field investigation was carried out in each zone by measuring depths and snow/water ratio. A volume of around 1100 × 10⁶ m³ of water was derived from snowmelt over the given period. This is equivalent to a precipitation rate of about 425 mm in the region, revealing the considerable portion of water that is derived from snowmelt.