Spatial differences in seasonal variation of the upper-tropospheric jet stream in the Northern Hemisphere and its thermal dynamic mechanism     

Xueyuan Kuang  Yaocun Zhang  Ying Huang  Danqing Huang 《Theoretical and Applied Climatology》2014,117(1-2):103-112

NCEP/NCAR reanalysis daily data from 1951 to 2008 are used in this study to reveal the spatial-asymmetric features in the seasonal variation of the upper-tropospheric jet stream (UTJS) and its thermal dynamic forcing mechanism. The jet occurrence percentage distribution of the UTJS demonstrates a spiral-like pattern in winter, but it is quasi-annular in summer. The jet occurrence percentage in the Eastern Hemisphere is larger than that in the Western Hemisphere, and its maximum area is located further south. The polar front jet stream (PJS) and subtropical jet stream (SJS) can be distinguished over the Northern Africa and Asian regions, whereas only one jet stream can be observed over the Western Pacific and Atlantic Ocean. Furthermore, a single peak pattern is found in the seasonal variation of the SJS occurrence frequency with the highest jet occurrence appearing in winter and the lowest in summer, while a double peak pattern is observed in the seasonal variation of the PJS occurrence, i.e., the jet occurrence reaches its peaks in autumn and spring for the PJS. Based on the thermal wind theory, air temperature gradient and atmospheric baroclinicity are calculated and compared with the jet occurrence variation to explore the thermal dynamic forcing mechanism for the UTJS variation. In addition, synoptic-scale transports of eddy heat and momentum are also calculated. The results indicate that the SJS variation is primarily determined by the air temperature gradient and atmospheric baroclinicity, while the PJS variation is under great influence of the transport of eddy heat and momentum over Northern Africa and East Asia. The UTJS variation over the area from 140E to 70W cannot be well individually explained by the air temperature gradient and atmospheric baroclinicity. Further analysis indicates that UTJS variation over this area is largely under control of combined effect of the transport of eddy heat and momentum as well as the atmospheric baroclinicity.  相似文献   

中国国家自然保护区土地覆被变化(英文)   总被引：3，自引：1，他引：2  

范泽孟  张轩  李婧  岳天祥  刘纪远  香宝  匡文慧 《地理学报(英文版)》2013,23(2):258-270

For preventing ecosystem degradation,protecting natural habitats and conserving biodiversity within the habitats,2588 nature reserves have been established in China at the end of 2010.The total area is up to 149.44 million ha and covers over 15% of Chinese terrestrial surface.Land-cover change,as the primary driver of biodiversity change,directly impacts ecosystem structures and functions.In this paper,180 National Nature Reserves(NNRs) are selected and their total area is 44.71 million ha,accounting for 29.9% of all NNRs in China.In terms of the ecosystem characteristics and their major protected object,all selected NNRs are classified into 7 types.A Positive and Negative Change Index of Land-cover(PNCIL) was developed to analyze the land-cover change of each NNRs type from the late 1980s to 2005.The results show that the land-cover of all selected NNRs types have degradated to a certain degree except the forest ecosystem reserves with a decreasing rate,but the rate of degradation alleviated gradually.The mean positive and negative change rates of land-cover in all core zones decreased by 0.69% and 0.16% respectively.The landscape pattern of land-cover in the core zones was more stable than that in the buffer zones and the experimental zones.Furthermore,the ecological diversity and patch connectivity of land-cover in selected NNRs increased generally.In short,the land-cover of 180 selected NNRs in China had a beneficial change trend after NNRs established,especially between 1995 and 2005.  相似文献   

日本福岛第一核电站核泄漏后放射性物质运动轨迹   总被引：3，自引：0，他引：3       下载免费PDF全文

岑况  陈媛  刘舒波  于扬 《地学前缘》2012,19(2):234-238

日本北部近海于2011年3月11日发生里氏9.0级地震,导致福岛第一核电站发生一连串事故并引发了核泄漏。日前此次核事故级别由事发后定的5级提至7级(核事故最高级别),核泄漏后放射性物质的扩散与迁移是目前关于核事故研究的热点之一。利用HYSPLIT模型模拟核爆炸后空气中放射性物质的运动轨迹发现核大气颗粒物主要运移方向为东和东北方向,进入太平洋上空,甚至美国境内,亦有朝南转西南运移的轨迹与趋势,使得放射性物质进入中国上空。根据历史气象资料对接下来的5—8月份大气颗粒物的运动轨迹进行预测,分析结果显示放射性物质随后可能往北,东北和西部运移,由于风向,降雨和洋流等的影响,将会继续影响中国,运移到中国的携带放射性物质的大气颗粒物主要来自高空。  相似文献   

含辉钼矿全岩样品Re-Os同位素定年研究:在北京大庄科钼矿床中的应用   总被引：1，自引：1，他引：0  

刘舒波  李超  岑况  屈文俊 《现代地质》2012,26(2):254-260

采用硝酸在比色管中对辉钼矿样品中Re含量进行初测的方法,测得辉钼矿标准样品JDC Re含量与推荐值在误差范围内基本一致,与传统的Carius管法相比,该方法具有简便快速的特点。传统的辉钼矿Re-Os同位素定年分析对象为辉钼矿单矿物,根据所测得的187Re/187Os值获得辉钼矿的Re-Os年龄,Re、Os在辉钼矿中大量富集,而在硅酸盐矿物中几乎没有,探索性地对含有辉钼矿的全岩样品进行Re-Os同位素定年,虽然所得Re、Os含量偏低,但187Re/187Os值不会变。该方法省去了选样过程花费的大量时间,避免了选样过程中可能造成的交叉污染。采用同位素稀释Carius管逆王水法探索性地对北京大庄科钼矿床中含辉钼矿全岩样品进行Re-Os同位素年龄测定,获得了(137.6±3.7)Ma精确的等时线年龄,与挑选出辉钼矿单矿物样品的Re-Os同位素等时线年龄(136.8±2.6)Ma吻合较好,直接厘定了大庄科钼矿的成矿时代。该年龄与矿区汉家川石英二长岩锆石U-Pb年龄一致,表明大庄科钼矿的形成与汉家川石英二长岩关系较为密切,为中国东部第二期大规模成矿作用的产物,形成于中国东部岩石圈伸展环境。  相似文献   

Late Cenozoic orogenic history of Western Qinling inferred from sedimentation of Tianshui basin, northeastern margin of Tibetan Plateau   总被引：1，自引：0，他引：1  

Xiuxi Wang  Jijun Li  Chunhui Song  Massimiliano Zattin  Zhijun Zhao  Jun Zhang  Yong Zhang  Kuang He 《International Journal of Earth Sciences》2012,101(5):1345-1356

The Western Qinling orogenic belt marks the northeastern margin of the Tibetan Plateau. Its late Cenozoic orogenic history is recorded in an excellent sedimentary sequence exposed in the Tianshui sub-basin of the Longzhong basin. According to the magnetostratigraphic analysis from the Yaodian and Lamashan sections, we speculate that the late Cenozoic Tianshui basin accumulated lacustrine/floodplain deposits from ~14.8 to ~2.6?Ma. In addition, detrital apatite fission-track thermochronologic and paleocurrent data reveal that the detritus of the Tianshui basin mostly derived from the Western Qinling and that the youngest population age represents a ~14?Ma volcanic intrusion, which can be related to the lithospheric deformation and uplift of the Tibetan Plateau. Furthermore, two stages of variations in depositional facies and average accumulation rates were attributed to the pulse uplift and deformation of the Western Qinling at 9.2–7.4 and ~3.6?Ma.  相似文献   

1996-2013年中国入境旅游市场时空演变研究：结构效应与空间效应     

张瑞英  席建超  葛全胜 《地域研究与开发》2014,(6)

在世界旅游大发展和全球一体化过程中,中国各区域的旅游吸引力、政策、营销等的不同引起入境旅游结构发生变化,从而引起中国入境旅游的时空格局不断发生变化。将中国分为八大旅游区域,采用偏移份额模型分析世界各大洲入境客源市场在八大旅游区域的结构效应和空间效应,试图阐述在中国旅游进程加快过程中入境旅游变迁的内在规律。结果表明：①1996—2010年来自各大洲的入境游客量在全国八大旅游区板块都表现为不断增长的趋势。2011—2013年入境游客量下滑,究其原因与中国旅游发展的内外部因素都有关,但总之中国入境旅游发展由不成熟及不稳定变得不断成熟起来。②总体来说,1996—2013年全国各区域入境旅游客源结构得到改善,但是北部沿海地区、南部沿海地区入境客源结构有恶化趋势,大西南地区自2005年以来入境旅游结构较差,大西北地区结构不稳定。③1996年以来,区域性增长速度差别越来越小。另外,中国各区域旅游成熟度和开放性在加强,各旅游区域的地理聚集性越来越差,中国八大旅游区域的各大洲入境旅游从偏好于某一区域向全国分散旅游趋势转化,分散旅游成为趋势。  相似文献   

Spatiotemporal characteristics,patterns and causes of land use changes in China since the late 1980s简   总被引：111，自引：20，他引：91  

LIU Jiyuan  KUANG Wenhui  ZHANG Zengxiang  XU Xinliang  QIN Yuanwei  NING Jia  ZHOU Wancun  ZHANG Shuwen  LI Rendong  YAN Changzhen  WU Shixin  SHI Xuezheng  JIANG Nan  YU Dongsheng  PAN Xianzhang  CHI Wenfeng 《地理学报(英文版)》2014,24(2):195-210

Land-use/land-cover changes （LUCCs） have links to both human and nature inter- actions. China＇s Land-Use/cover Datasets （CLUDs） were updated regularly at 5-year inter- vals from the late 1980s to 2010, with standard procedures based on Landsat TM／ETM＋ im- ages. A land-use dynamic regionalization method was proposed to analyze major land-use conversions. The spatiotemporal characteristics, differences, and causes of land-use changes at a national scale were then examined. The main findings are summarized as fol- lows. Land-use changes （LUCs） across China indicated a significant variation in spatial and temporal characteristics in the last 20 years （1990-2010）. The area of cropland change de- creased in the south and increased in the north, but the total area remained almost un- changed. The reclaimed cropland was shifted from the northeast to the northwest. The built-up lands expanded rapidly, were mainly distributed in the east, and gradually spread out to central and western China. Woodland decreased first, and then increased, but desert area was the opposite. Grassland continued decreasing. Different spatial patterns of LUC in China were found between the late 20th century and the early 21st century. The original 13 LUC zones were replaced by 15 units with changes of boundaries in some zones. The main spatial characteristics of these changes included （1） an accelerated expansion of built-up land in the Huang-Huai-Hai region, the southeastern coastal areas, the midstream area of the Yangtze River, and the Sichuan Basin; （2） shifted land reclamation in the north from northeast China and eastern Inner Mongolia to the oasis agricultural areas in northwest China; （3） continuous transformation from rain-fed farmlands in northeast China to paddy fields; and （4） effective- ness of the ＂Grain for Green＂ project in the southern agricultural-pastoral ecotones of Inner Mongolia, the Loess Plateau, and southwestern mountainous areas. In the last two decades, although climate change in the north affected the change in cropland, policy regulation and economic driving forces were still the primary causes of LUC across China. During the first decade of the 21st century, the anthropogenic factors that drove variations in land-use pat- terns have shifted the emphasis from one-way land development to both development and conservation. The ＂dynamic regionalization method＂ was used to analyze changes in the spatial patterns of zoning boundaries, the internal characteristics of zones, and the growth and decrease of units. The results revealed ＂the pattern of the change process,＂ namely the process of LUC and regional differences in characteristics at different stages. The growth and decrease of zones during this dynamic LUC zoning, variations in unit boundaries, and the characteristics of change intensities between the former and latter decades were examined. The patterns of alternative transformation between the ＂pattern＂ and ＂process＂ of land use and the causes for changes in different types and different regions of land use were explored.  相似文献   

全球油气开采诱发地震的研究现状与对策     

张捷  况文欢  张雄  莫程康  张东晓 《地球与行星物理论评》2021,(3):239-265

人工诱发地震现象已经有很久的历史.水库蓄水、采矿、地热开发、从地下提取液体或气体,或将液体注入地球内部都可能诱发地震.大量地震监测数据与科学分析结果显示:美国俄克拉何马州的地震剧增主要与页岩油气开采的废水回注量相关;加拿大阿尔伯塔省的地震剧增主要与页岩油气开采水力压裂的工作量相关;而荷兰罗宁根天然气田的传统天然气开采也同样诱发了较强的地震活动.在中国四川盆地的页岩油气开发区域,地震活动近几年也大幅度增强,但目前监测与科研工作较少,对某些地震成因尚有争议.目前研究诱发地震问题已成为学术界与工业界的一门专业学科.推断诱发地震,除了分析时空分布与工业活动的相关性之外,本文综述了该领域基于地震学、地质动力学、构造地质学的多种分析方法.如何在油气开采过程中减少诱发地震的灾害影响成为当前相关各界极为关注的科研问题,本文介绍了多个国家或地区建立的控制诱发地震的管理系统、基于地震大数据的诱发地震概率预测方法,以及基于地球物理与地质信息的综合诱发地震风险评估方法,并对我国控制诱发地震问题提出建设性意见.  相似文献   

德国北部盆地晚侏罗世沉积环境及古气候分析^*          下载免费PDF全文

白华青  旷红伟  柳永清  吴峰 《古地理学报》2021,23(2):405-420

德国北部盆地上侏罗统广泛发育,但野外露头地层普遍出露不全。Hildesheimer Wald地区Wendhausen 6井和Süntel山地区Eulenflucht 1井完整钻遇了上侏罗统牛津阶和启莫里阶地层,为分析该区晚侏罗世沉积演化过程及其所反映的古环境变化规律提供了丰富的资料。通过岩心描述和岩石薄片镜下观察,根据不同层段的颗粒成分、生物组合特征、沉积结构和构造等特征,在2口井的岩心中共划分出14个岩石类型,分别形成于碳酸盐岩斜坡和三角洲环境。建立了该区牛津阶和启莫里阶垂向沉积演化序列,垂向上由Heersum组到Süntel组,沉积环境逐步由外陆棚、内陆棚、临滨过渡到了开阔台地、潮坪环境,表现出了相对海平面降低的进积过程。同时对不同沉积相中保存较好的以低镁方解石为主要成分的牡蛎壳进行原位Mg/Ca值(古温度指标)测试,得出该区牛津期至启莫里期总体表现出了古气候变暖的趋势,且共有3次气候变暖过程。这一古气候变化与由沉积相分析得出的古气候变化一致,且同苏格兰、俄罗斯台地古温度变化趋势有很好的对应关系,表明古气候是控制该区沉积演化的一个重要因素,且牡蛎壳Mg/Ca值可以做为一个古气候指示指标应用于其他地区的古气候分析中。  相似文献   

云南云县地震台迁建观测站概述          下载免费PDF全文

曹白伦  匡福江 《地震科学进展》2022,52(4):176-182

大临铁路的修建,对云县地震台地震观测环境造成严重干扰.为支持重大项目建设,妥善处理铁路建设与地震观测环境保护的关系,云南省地震局确定以"主体保住云县地震台,受影响大的测项迁出到合适的场地"为原则来解决云县地震台观测环境保护问题.迁建过程中,地震部门高度重视,建立协调推进机制,并依法科学决策;台站干部职工主动介入,密切配...  相似文献