近50年我国冰雹年代际变化及北方冰雹趋势的成因分析

利用1958-2007年中国755个站的逐日冰雹资料和同期NCEP/NCAR再分析资料及环流特征量,研究了中国近50年冰雹时空变化特征。研究表明,20世纪70年代末、80年代初我国冰雹呈下降趋势,尤其是80年代末以来降雹次数基本低于近50年的平均值,其中我国北方冰雹下降趋势比南方显著,除黄淮、江淮、长江中下游和华南地区外,全国大部分地区冰雹下降趋势都通过了0.05的显著性水平检验,尤其是东北、华北、西北和青藏高原中东部地区。分析表明,20世纪70年代末大尺度环流系统的一系列调整是我国北方冰雹减少的主要原因,200 hPa高空西风急流南移,导致我国北方纬向风场减弱,风速垂直切变减小,对流减弱;850 hPa高度场升高不利于极地冷空气南下和对流系统的建立;同时副高增强,极涡减弱使大气层结稳定,冷空气活动减弱。伴随着大尺度环流的调整,局地垂直温度场结构的变化是影响降雹次数的一个重要原因,局地0℃线和-20℃线之间过冷却水滴累积区距离缩短,不利于雹粒充分地碰并增长,这对东北、华北和西北西部降雹出现显著减少具有十分重要的作用。     

Agricultural drought risk analysis based on three main crops in prefecture-level cities in the monsoon region of east China

Drought, a frequent environmental disaster in the monsoon region of east China, significantly affects the agricultural economy. In recent years, researchers have emphasised drought risk management. This paper presents a preliminary method to analyse the risk of agricultural drought with regard to the loss of three main crops in individual prefecture-level cities in the monsoon region of east China. In this study, the agricultural drought risk is assessed by developing the index of consecutive rainless days and establishing loss rate curves based on the historical drought data from 1995 to 2008. The results show that the North China is seriously affected by drought hazard. Northeast China is the most sensitive to drought due to its large sown crop areas and weak irrigation. Approximately 11 % of the cities are in the extreme risk category; this category includes 26 % of the cultivated land area and 11 % of the total crop yields in the region. Twenty-three per cent of the cities, accounting for 28.5 % of the total cultivated land area and 26.4 % of the crop yields of the study area, are in high-risk areas, and 77 % of the cities with high and extreme risk levels are distributed in North and Northeast China. Moreover, 64 % of the cities in the monsoon region of East China are in moderate- and low-risk levels. These cities are primarily located south of the Yangtze River. In conclusion, minimising the risk of agricultural drought must be emphasised in northern China because of the high level of risk.     

新疆西天山博罗科努成矿带岩浆岩时空分布、 构造演化与成矿响应

博罗科努成矿带位于新疆西天山北缘,近年来找矿成果突出.在充分收集前人研究成果的基础上,初步总结了博罗科努带岩浆岩时空分布特点及其年龄资料,重点分析了与成矿关系密切的晚古生代岩浆作用的性质.博罗科努带地质历史与北天山洋的演化密切相关,前寒武纪统一基底形成,北天山洋打开.寒武纪为被动陆缘环境,北天山持续扩张.奥陶纪北天山洋向伊犁地块之下俯冲,该带进入大陆弧演化阶段.泥盆纪—晚石炭世早期为俯冲高峰期,引发了一系列钙碱性的岩浆活动;早二叠世该带已进入陆相环境,但北天山洋残余洋盆的俯冲持续到中二叠世;晚二叠世全面进入陆内演化阶段,区域构造应力性质由挤压变为伸展.伴随洋-陆构造演化,形成了莱历斯高尔和阿希两大矿集区,分别对应2套成矿系统:与侵入岩浆活动有关的矽卡岩-斑岩-热液脉型铁、铜、钼、金、锑、铅、锌成矿系统和与次火山热液活动有关的浅成低温热液-斑岩型金、铅、锌、铜成矿系统.     

Common envelope evolution: where we stand and how we can move forward

This work aims to present our current best physical understanding of common-envelope evolution (CEE). We highlight areas of consensus and disagreement, and stress ideas which should point the way forward for progress in this important but long-standing and largely unconquered problem. Unusually for CEE-related work, we mostly try to avoid relying on results from population synthesis or observations, in order to avoid potentially being misled by previous misunderstandings. As far as possible we debate all the relevant issues starting from physics alone, all the way from the evolution of the binary system immediately before CEE begins to the processes which might occur just after the ejection of the envelope. In particular, we include extensive discussion about the energy sources and sinks operating in CEE, and hence examine the foundations of the standard energy formalism. Special attention is also given to comparing the results of hydrodynamic simulations from different groups and to discussing the potential effect of initial conditions on the differences in the outcomes. We compare current numerical techniques for the problem of CEE and also whether more appropriate tools could and should be produced (including new formulations of computational hydrodynamics, and attempts to include 3D processes within 1D codes). Finally we explore new ways to link CEE with observations. We compare previous simulations of CEE to the recent outburst from V1309 Sco, and discuss to what extent post-common-envelope binaries and nebulae can provide information, e.g. from binary eccentricities, which is not currently being fully exploited.     

Cooling effect of convection-intensifying composite embankment with air doors on permafrost

One of the main construction problems in permafrost regions is protecting permafrost thermal stability. Although ventilating ducts and crushed-rock layers were successfully used in railway embankment construction, their effects might not meet large-width expressway requirements. The convection-intensifying composite embankment composed of perforated ventilation ducts and crushed-rock layers was numerically studied to investigate its cooling effects. Adopting a numerical model, the temperature fields for two kinds of composite embankment with and without air doors were analyzed considering air flow and heat transfer characteristics in porous media. The results show that wind velocity in the crushed-rock zone is intensified by the perforated ventilation duct. The underlying permafrost temperature obviously decreases, and the 0 °C isotherm position rises significantly due to composite embankment. The composite embankment with air doors is more effective than that without air doors. Therefore, the new convection-intensifying composite embankment is potentially a highly efficient cooling measure for construction in permafrost regions.     

Diagnostic model construction and example analysis of habitat degradation in enclosed bay: I. diagnostic model construction

Presently, research is lacking regarding the diagnosis and evaluation of habitat degradation in enclosed bay systems. We established a diagnostic model for enclosed bay habitat degradation （EBHD model） using a multi-approach integrated diagnostic method in consideration of driving force-pressure- state-influence-response. The model optimizes the indicator standardization with annual average change rate of habitat degradation as the basic element, to reflect accurately the impact of the change and speed of degradation on the diagnostic results, to quantify reasonably the contribution of individual diagnostic indicator to habitat degradation, and to solve the issue regarding the influence of subjective factors on the evaluation results during indicator scoring. We then applied the EBHD model for the Sansha Bay in Fujian Province, China, evaluated comprehensively the situation of habitat degradation in the bay, and screened out the major controlling factors in the study area. Results show that the diagnostic results are consistent in overall with the real situation of the study area. Therefore, the EBHD model is advantageous in terms of objectivity and accuracy, making a breakthrough in diagnosis and evaluation for habitat degradation in enclosed bay systems.     

Diagnostic model construction and example analysis of habitat degradation in enclosed bay: II. spatiotemporal variations in habitat degradation in Sansha Bay

The process of habitat degradation varies in habitat type and driving force which shows certain spatial and temporal heterogeneity on regional scales. In the present study, a new diagnostic model for enclosed bay habitat degradation was established, with which the spatial and temporal variation patterns of habitat degradation during 1991–2012 in Sansha Bay, Fujian, China was investigated. The results show that anthropogenic disturbance is the major controlling factor for the habitat degradation in large temporal heterogeneity in the bay. On the other hand, the habitat degradation experienced signifi cant spatial variations among six sub-bays. Under the joint action of temporal and spatial heterogeneity, the degradation trend in growing scale shows a more signifi cant correlation with the distribution of local leading industries along shorelines. Therefore, we quantifi ed the main characters of habitat degradation in Sansha Bay, and have understood the relationship between the status of habitats spatio-temporal variation value and the main controlling factor leading to the changes. However, a defi ciency of this research is the lack of or inaccessible to the detailed data, which shall be better solved in the future study for accessing more data from more sources.     

The Summer Snow Cover Anomaly over the Tibetan Plateau and Its Association with Simultaneous Precipitation over the Mei-yu–Baiu region

The summer snow anomalies over the Tibetan Plateau （TP） and their effects on climate variability are often overlooked,possibly due to the fact that some datasets cannot properly capture summer snow cover over high terrain.The satellite-derived Equal-Area Scalable Earth grid （EASE-grid） dataset shows that snow still exists in summer in the western part and along the southem flank of the TP.Analysis demonstrates that the summer snow cover area proportion （SCAP） over the TP has a significant positive correlation with simultaneous precipitation over the mei-yu-baiu （MB） region on the interannual time scale.The close relationship between the summer SCAP and summer precipitation over the MB region could not be simply considered as a simultaneous response to the Silk Road pattern and the SST anomalies in the tropical Indian Ocean and tropical central-eastern Pacific.The SCAP anomaly has an independent effect and may directly modulate the land surface heating and,consequently,vertical motion over the western TP,and concurrently induce anomalous vertical motion over the North Indian Ocean via a meridional vertical circulation.Through a zonal vertical circulation over the tropics and a Kelvin wave-type response,anomalous vertical motion over the North Indian Ocean may result in an anomalous high over the western North Pacific and modulate the convective activity in the western Pacific warm pool,which stimulates the East Asia-Pacific （EAP） pattern and eventually affects summer precipitation over the MB region.     

Variation of Bioaccumulation Ability of 2,2’,4,4’- Tetrabromodiphenyl Ether by Marine Diatom Skeletonema costatum Under Different N：P Ratios

The growth, biochemical content and bioaccumulation quantity of 2,2’,4,4’-tetrabromodiphenyl ether （BDE-47） in Skeletonema costatum were studied under different N：P ratios （1, 4, 16, 64 and 128）. All cellular biochemical contents of S. costatum presented decreasing trend over cultivation time. At early stage of cultivation, the cellular protein, carbohydrate and lipid in S. co-statum presented higher values in treatments of N：P=4 and 16. However, they were lower in these treatments at the late stage, but higher in treatments N：P=1 and 128. Similarly, BDE-47 levels per cell of S. costatum were higher in treatments of N：P=4 and 16 at early stage of cultivation, which were 3.8 and 3.7 ng （106 cells）-1, respectively. At the middle stage of cultivation, the BDE-47 level per S. costatum cell lowered;and it further reduced in the treatments of N：P=4 and 16 at the late stage with the values 0.6 and 0.5 ng （106 cells）-1, respectively. However, it rose in N：P=128, reaching up to 2.3 ng （106 cells）-1. Compared with BDE-47 per cell, BDE-47 per algal volume under different N：P ratios did not present obvious difference. The quantity BDE-47 accumulated per cell of S. co-statum was positively correlated with protein, carbohydrate and lipid per cell; meanwhile, the BDE-47 per volume had a positive correlation with biochemical content per volume. The variation of bioaccumulation ability of BDE-47 in S. costatum can be ex-plained by biochemical changes due to N：P ratios.     

基于罗德里格矩阵的混合最小二乘方法在三维激光中的应用

介绍了基于罗德里格矩阵的混合最小二乘坐标转换模型及精度,通过三维激光点云配准与坐标转换实验的结果表明,基于罗德里格矩阵的混合最小二乘方法的效果及精度明显高于基于罗德里格矩阵的最小二乘方法,说明该方法的可行性。