RESEARCH PROGRESS ON THE STRUCTURE AND INTENSITY CHANGE FOR THE LANDFALLING TROPICAL CYCLONES   总被引：2，自引：2，他引：0  

陈联寿 《热带气象学报(英文版)》2012,18(2):113-118

Landfalling tropical cyclones(LTCs)include those TCs approaching the land and moving across the coast.Structure and intensity change for LTCs include change of the eye wall,spiral rain band,mesoscale vortices,low-layer shear lines and tornadoes in the envelope region of TC,pre-TC squall lines,remote rain bands,core region intensity and extratropical transition(ET)processes,etc.Structure and intensity change of TC are mainly affected by three aspects,namely,environmental effects,inner core dynamics and underlying surface forcing.Structure and intensity change of coastal TCs will be especially affected by seaboard topography,oceanic stratification above the continental shelf and cold dry continental airflow,etc.Rapid changes of TC intensity,including rapid intensification and sudden weakening and dissipation,are the small probability events which are in lack of effective forecasting techniques up to now.Diagnostic analysis and mechanism study will help improve the understanding and prediction of the rapid change phenomena in TCs.  相似文献   

济阳坳陷三种典型滩坝相的空间分布模式   总被引：3，自引：0，他引：3  

马立祥  邓宏文  林会喜  冯兴雷  涂智杰 《地质科技情报》2009,28(2)

基于对渤海湾盆地济阳坳陷车镇凹陷和沾化凹陷重点区块沙二段和沙四段滩坝相的解剖研究成果,展示了陆相断陷盆地不同演化阶段滩坝相的3种空间分布模式:①断-坳期碟形洼陷细粒碎屑岩滩坝相分布模式,这种分布模式发育于车镇凹陷大王北洼陷的沙二段,是一种浅水漫湖式细粒碎屑岩滩坝相沉积,可分为滩、坝主体、坝侧缘、坝间4种沉积微相;②断-坳期双断对称中隆型洼陷滩坝相分布模式,这种分布模式发育于沾化凹陷东部孤北洼陷的沙二段,受中部潜山隆起的控制作用明显,在中部潜山周缘的缓坡部位以碳酸盐岩滩坝相沉积为主,两侧为近似对称的、从岸边-中部依次发育粗粒扇三角洲相-中细粒碎屑岩滩坝相沉积;③断陷期单断非对称式水下中隆型洼陷滩坝相分布模式,这种分布模式发育于孤北洼陷桩西地区的沙四段,其东部次洼以粗粒扇三角洲和扇三角洲间为主,中部水下低隆起处及其周缘形成浅湖细粒碎屑岩滩坝相沉积,而在西部斜坡则以滩坝相沉积为主.这3种模式对于寻找以滩坝型为储层的岩性-地层圈闭具有参考意义.  相似文献   

Erosion and Accretion of a Placer Mining Beach of SW Indian Coast     

K. Rajith  N. P. Kurian  K. V. Thomas  T. N. Prakash  T. S. S. Hameed 《Marine Geodesy》2013,36(2):128-142

The erosion/accretion pattern in a placer mining beach on the southwest Indian coast was monitored for five years to study the role of different driving forces. The beach has maximum width during the fair weather months and least in the rough monsoon months. Apart from hydrodynamic processes, sand mining and presence of sea wall are found to be the driving forces for erosion/accretion. Impact of sand mining is not felt on the beach when the mining is within an optimum level, equivalent to the natural replenishment. It is concluded that, though sand mining will cause erosion in the innershelf, the time taken for a measurable impact can be long if the mining volumes are much less than the annual volume changes.  相似文献   

Sedimentation and morphological changes at Yuantuojiao Point,estuary of the North Branch,Changjiang River   总被引：3，自引：1，他引：2  

XIE Li  ZHANG Zhenke  ZHANG Yunfeng  WANG Yaping  HUANG Xianjin 《海洋学报(英文版)》2013,32(2):24-34

The North Branch, separated by the Chongming Island, was once the main channel in the estuary of the Changjiang River. Reclamation and a decrease in runoff to the North Branch had led to the narrowing and shallowing of the channel. The Yuantuojiao Point is located at the intersecting point connecting the North Branch of the Changjiang River and the Jiangsu coastline. Erosion cliffs are developed between the typical silty-muddy tidal flat and the salt marsh occupied by Spartina alterniflorea, and this has changed rapidly over the past few years. The sediment grain size analysis results of the surficial and two core samples indicate that the Yuantuojiao Point tidal flat experienced continuous accretional processes. Based upon 137 Cs analysis results of the YT and YY Cores sampled from the tidal flat at the Yuantuojiao Point, the average sedimentation rate of the YT Core was 2.30 cm/a from 1963 to 2007, and 2.38 cm/a from 1954 to 2007 for the YY Core. The sedimentation rates of both core locations have declined since the 1960s corresponding to the seaward reclamation at the Yuantuojiao Point. The average sedimentation rates at the Yuantuojiao Point were similar to that of the silty-muddy tidal flat at the northern Jiangsu coast, but lower than that of the south of the Changjiang River Estuary. According to field morphological investigations from 2006 to 2008 on the salt marsh at the Yuantuojiao Point, cliffs retreated markedly by storm surges and disappeared gradually because of the rapid sedimentation on the silty-muddy tidal flat. The maximum annual retreat reached 10 m. The recent sedimentation and morphological changes of the Yuantuojiao Point tidal flat not only displayed the retreat of the salt marsh and the disappearance of cliffs, but also was accompanied by rapid sedimentation of the silty-muddy tidal flat and the salt marsh, indicating the responses to the tidal currents, storm surges, Spartina alterniflorea trapping sediments and large-scale reclamation. The sediment grain size and their trends, southward coastal flow, and sandspits of the longshore bars suggest that the main sediment source at the Yuantuoijao Point, estuary of the North Branch was possibly from the Changjiang River before 1958, since then, it has been from the south of the submarine radial sand ridges of the southern Huanghai Sea (Yellow Sea).  相似文献   

HEIMDALL'S STONES AT VITEMÖLLA IN SE SWEDEN AND THE CHRONOLOGY AND STRATIGRAPHY OF THE SURROUNDINGS     

BY NILS-AXEL MÖRNER  BOB G. LIND  GÖRAN POSSNERT 《Geografiska Annaler: Series A, Physical Geography》2009,91(3):205-213

Heimdall's Stones at Vitemölla is an archaeological monument of stones arranged in circles and where sightlines can be identified of the sunrise and sunset at winter and summer solstices and spring and autumn equinoxes. Therefore, this stone monument is likely to have served as an archaeoastronomic observatory. It is founded in a fossil land surface now covered by half a metre of eolian sand. In order to date this sand drift, sediment coring was performed in the nearby Sandefloen bog. Seven levels were subjected to AMS C14 dating. The first sand drift, correlated with the sand drift covering Heimdall's Stones, was dated at 500–600 cal. bc . Consequently, the observatory has to date back to the Bronze Age, fitting well with its Sun cult and with the rock carvings recorded on the individual stones. At the seashore 500 m east of the observatory and the bog, we were able to reconstruct the sea-level changes. In conclusion, we combine the recorded sea-level changes with the C14-dated bog stratigraphy and the observed stratigraphy at Heimdall's Stones (covering an area of 500×500 m) into one unified picture. The chronostratigraphic position of Heimdall's Stones agrees well with the dating of the Kivik grave. The Vitemölla area is likely to have been an important cultural centre in the Bronze Age.  相似文献   

中国北方近57年气温时空变化特征   总被引：28，自引：2，他引：26  

王海军  张勃  赵传燕  靳晓华  王兴梅  戴声佩  王亚敏  康淑媛  刘艳艳  李丹 《地理科学进展》2009,28(4)

通过分析中国北方近57年来气温时空变化特征,结合GIS空间分析技术和数理统计理论,对中国北方气温变化进行定量化分析,阐述其时空演变规律。结果表明:近57年来中国北方气温总体呈上升趋势,升温趋势最快的是东北地区(0.25℃/10a),最慢的是西北东区(0.12℃/10a)。各区年均、1月、7月气温的增温趋势呈非对称性,年均气温的升高主要得益于1月气温的贡献,7月各区升温趋势普遍较慢;中国北方年均气温变化存在突变现象,东北区是在1994年(a=0.05),华北区是在1997年(a=0.05),西北西和西北东分别为在1996年和1997年(a=0.05);年均气温变化具有明显的周期性,东北区分别以21a、6a、11a为第一、第二、第三主周期,华北区气温周期为22a,西北西区周期为12a,西北东区第一、第二、第三主周期分别为15a、8a、5.5a;中国北方各区气温变化一致性较强,都呈现上升趋势,但各区之间相关关系存在差异,东北和华北年均气温相关系数达到0.79(a=0.01),1月东北区和西北西区相关系数为0.19,7月东北区和西北东区的相关系数为0.26,未达到显著水平。  相似文献   

长江上游干支流近期水沙变化及其与水库修建的关系   总被引：7，自引：0，他引：7  

许炯心 《山地学报》2009,27(4)

基于水文站实测的长系列水沙资料,运用统计方法研究了长江上游干支流的近期水沙变化.屏山站年输沙量的变化自1999年以后开始减小,扭转了1980～1998年的增加趋势.高场站年输沙量由1990～2000年的减小趋势,变化为2000～2007年的增大趋势.北碚站的年输沙量呈进一步减少的趋势.武隆站年输沙量改变了1990～2000年的增加趋势,2000～2007年显著减小.宜昌站的年输沙量延续了从20世纪80年代中期以来的减少趋势,2002～2007年急剧减小.采用输沙量-径流最双累积曲线方法进行了分析,发现各站双累积曲线上最近一次转折点的出现,均与水库的修建有关.基于双累积曲线估算了近期各站的减沙量(或增沙量).研究还发现,近期屏山、北碚、武隆、宜昌4站含沙量均呈现减小趋势,与水库的拦沙作用密切相关.但是,岷江近期水电梯级开发的大规模展开,巨量弃土、弃渣进入河道,导致了2002～2007年间含沙量的增大.建立了宜昌站年输沙量与长江上游流域内累计水库库容量及宜昌站年径流量之间的回归方程,估算出它们对于长江上游产沙量变化的贡献率分别为71.4%和28.6%.这表明,水库拦沙是导致长江上游产沙量减小的主要原因.  相似文献   

基于农户空间行为变迁的乡村人居环境研究   总被引：11，自引：0，他引：11  

李伯华  曾菊新 《地理与地理信息科学》2009,25(5)

城市化进程中乡村社会经济取得巨大成就的同时,也伴随出现了一些新的现象、问题与发展趋势,如乡村人居环境持续恶化等.该文从农户空间行为变迁的角度建立了乡村人居环境研究的分析框架,探讨了农户空间行为从传统到现代演化的过程和原因,认为农户空间行为变迁是乡村人居环境演化的主要驱动力,而实现乡村人居环境优化目标就是从农户空间行为调控的内在机制出发,制定引导农户空间行为的相关政策和建议.  相似文献   

Spatio-temporal patterns of land use change along the Bohai Rim in China during 1985–2005     

GUO Liying  WANG Daolong  QIU Jianjun  WANG Ligang  LIU Yu 《地理学报》2009,19(5):568-576

Based on TM image data and other survey materials, this paper analyzed the spatiotemporal patterns of land use change in the Bohai Rim during 1985–2005. The findings of this study are summarized as follows: (1) Land use pattern changed dramatically during 1985–2005. Industrial and residential land in urban and rural areas increased by 643,946 hm2, of which urban construction land had the largest and fastest increase of 294,953 hm2 at an annual rate of 3.72%. (2) The outward migration of rural population did not prevent the expansion of residential land in rural areas by 184,869 hm2. This increase reveals that construction of rural residences makes seriously wasteful and inefficient use of land. (3) Arable land, woodland and grassland decreased at a rate of –0.02%, –0.12% and –1.32% annually, while unused land shrank by 157,444 hm2 at an annual rate of –1.69%. (4) The change of land use types showed marked fluctuations over the two stages (1985–1995 and 1995–2005). In particular, arable land, woodland and unused land experienced an inversed trend of change. (5) There was a significant interaction between arable land and woodland. Industrial construction land in urban and rural areas showed a net trend of increase during the earlier period, but only adjustment to its internal structure during the second period. The loss of arable land to the construction of factories, mines and residences took place mainly in the fringe areas of large and medium-sized cities, along the routes of major roads, as well as in the economically developed coastal areas in the east. Such changes are closely related to the spatial differentiation of the level of urbanization and industrialization in the region.  相似文献   

Analyses of spring mean circulations for major and minor dust storm years in China–Mongolia area     

MinHong Song  ZhengAn Qian  Ying Cai  ChungMing Liu 《寒旱区科学》2009,1(4):0361-0371

To better understand the dust storm (hereafter DS) inducing circulation in the China–Mongolia (CM) DS activity area, the spring mean circulation features and differences on lower levels in three subregions of the CM DS area for the major- and minor-DS years have, as a whole (not partly), been analyzed, utilizing the National Centers for Environmental Prediction and the National Center for Atmospheric Research (NCEP/NCAR) reanalyzed gridded data, the observed DS frequency data in the CM area, and the composite analysis method. The main conclusions are as follows: (1) Judging from the differences in the DS-inducing systems, dust origins, paths of invading cold air, and main DS-strike areas, the whole CM DS area is roughly divided into the three subregions: the East-, Middle- and West-CM subregions (in this paper, referred to as E-, M-, and W-CM). (2) In major DSs during spring over the E-CM, the middle- and lower-level troughs or cyclones over the Japan Sea and northeastern China (NEC) dominate. The invading cold air along the northeastern (NE) or north by east (NE) path often causes the DS in the E-CM region. But nearly the opposite is true in minor DS during spring in E-CM. (3) In the major DS during spring over the M-CM region, the Mongolian troughs or cyclones are the main DS-inducing systems. The strong invading cold air along the northwestern (NW)- or north by west (Nw) path causes the DSs in the M-CM region. (4) In the major DSs during spring over the W-CM region, the South Xinjiang heat lows prevail, the intruding cold air has a western path, and creates the DSs in South Xinjiang. (5) In the past 50 years, the DSs over the M-CM region have had the most severe impact on the preceding three subregions of the CM DS area. Overall, DS activities over all of three regions of the CM area decreased in the past (particularly, over M- and W-CM regions since the mid-1980s. But there existed a short and sudden increasing in E-CM in the years 2000–2002. (6) It is circulation changes and desertification evolutions that cause the yearly and decadal changes of DS in CM area, especially the former. With the backdrop of global warming in the future, perhaps the decreased DS activities over M- and W-CM will persist for some time again, and special attention should be paid to ones over E-CM or to the individual DS events over M- and W-CM.  相似文献