利用LPAC图分析北半球夏半年环流季节转换及异常     

蔡新玲王盘兴  杜继稳刘子臣 《南京气象学院学报》2005,28(5):710-716

用NCEP／NCAR再分析月平均风、压场资料得到1958—1997年5—10月月际场的局地型相似系数（LPAC）。多年平均LPAC表明了对流层和平流层低层印度夏季风环流的建立、东亚夏季风环流的北进和南亚高压上高原的过程，这些区域LPAC值较同纬度非季风区明显偏低。在平流层中层，夏季型环流表现出纬向对称性和由高纬向低纬的传播特征。对东亚LPAC气候变率时空剖面及3个涝年LPAC异常的分析反映出环流型季节转变异常及其与东亚月降水异常的关系。  相似文献   

东亚地区春冬季与夏季大气环流异常相互关系的研究   总被引：6，自引：2，他引：6       下载免费PDF全文

孙力  安刚 《应用气象学报》2002,13(6):650-661

利用1951~2000年共50年的北半球500 hPa月平均高度距平场资料和奇异值分解技术（SVD），重点对东亚地区季节间大气环流异常的相互关系进行了初步探讨。结果表明，东亚地区季节间大气环流异常存在着较为密切的关联，并且这种明显的非同步联系具有时空相关显著的特点，尤其是夏季大气环流异常与其前冬和前春大气环流异常的联系更为密切。当前冬和前春北半球东亚大槽和北美大槽及蒙古高压偏强（或偏弱），极涡偏弱（或偏强），中高纬度盛行经向环流（或纬向环流），以及低纬和热带地区高度正距平（或负距平）明显时，则对应于夏季东亚地区西太平洋副高和鄂霍次克海阻高强度偏强（或偏弱），位置偏南（或偏北），贝加尔湖阻高强度也偏强（或偏弱），但位置偏西（或偏东）的大尺度环流形势出现。当春季北半球大气环流具有上述特点以及夏季鄂霍次克海阻高和西太平洋副高强度偏强（或偏弱），位置偏南（或偏北），且极涡较弱（较强）时，则东亚地区秋季大气环流对应于蒙古高压加强（或较弱），西太平洋副高减弱（或加强），并向南和向东移动（或移动较慢），极涡向南扩散（或扩散减弱），大气环流向冬季过渡加快（或减慢）。另外，大气环流异常还具有一定的持续性特征。  相似文献   

Physical and chemical dynamics of temporary ponds on a calcareous plateau in Thuringia, Germany     

Jens Arle   《Limnologica》2002,32(2)

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新疆塔里木河下游植物群落逆向演替分析   总被引：29，自引：10，他引：29  

刘加珍  陈亚宁 《干旱区地理》2002,25(3):231-236

通过对塔里木河中下游沿河植物群落的调查分析及地下水位下降对地表植被生态过程影响的研究，探讨塔里木河下游近几十年来植被的逆向演替过程，并划分出不同的演替阶段。根据草、灌、乔植被对地下水位具有不同的适应能力，塔里木河下游植物群落退化顺序也不相同，首先是草本退化，其次是灌木退化，再者是乔木退化。经调查分析表明，塔里木河下游植物群落的逆向演替顺序为：矫灌草群落阶段→乔灌群落阶段→乔木或灌木少阶段，在逆向演替过程中，各阶段有规律地进行，群落结构特征、种类组成也都发生了明显的变化。  相似文献   

青藏高原土壤水热分布特征及冻融过程在季节转换中的作用   总被引：21，自引：0，他引：21  

杨梅学  姚檀栋  何元庆 《山地学报》2002,20(5):553-558

利用GAME-Tibet期间所取得的高分辩率土壤温度和含水量资料，对青藏高原（主要是藏北高原）土壤水热分布特征及冻融过程在季节转换中的作用进行了分析。指出藏北高原4cm学深处土壤在10月份开始冻结，次年4-5月份开始消融，冻结持续时间长达5-7个月。冻结过程有利于土壤维持其水分，因此，在刚刚开始消融时土壤含水量仍然很高。从而为夏季风爆发前土壤通过蒸发向大气提供水分打下了基础。指出土壤冻融过程可能在高原季节转换中起着重要作用。  相似文献   

The application of GPR to barrier-lagoon sedimentation study in Boao of Hainan Island     

YIN Yong  ZHU Dakui  TANG Wenwu  Martini I. Peter 《地理学报(英文版)》2002,12(3)

Sedimentary successions and internal structure of the coastal barrier-lagoon system of Boao, eastern Hainan Island were studied through utilizing data from test holes and trenches and ground-penetrating-radar (GPR) profiles. During late Pleistocene, fluvial and delta plains developed over an unevenly eroded bedrock during low sea level stand, followed by the formation of littoral and lagoon facies and defined coastal barrier-lagoon-estuary system during the post-glacial uppermost Pleistocene-lower Holocene eustatic rise of the sea level, and the upper Holocene high stand. GPR results show that Yudaitan, a sandy coastal bar backed by a low-laying land (shoal) just east of the active lagoon, is a continuous, parallel and slightly-wavy reflectors indicating homogeneous sandy or sandy gravel sediments, and inclined reflectors partly caused by progradation and accumulation of beach sand and gravel. Quasi-continuous, hummocky and chaotic reflectors from the shoal of Nangang village correspond to mixed accumula  相似文献   

The application of GPR to barrier-lagoon sedimentation study in Boao of Hainan Island     

YIN Yong  ZHU Dakui  TANG Wenwu  Martini I. Peter 《地理学报》2002,12(3):313-320

Sedimentary successions and internal structure of the coastal barrier-lagoon system of Boao, eastern Hainan Island were studied through utilizing data from test holes and trenches and ground-penetrating-radar (GPR) profiles. During late Pleistocene, fluvial and delta plains developed over an unevenly eroded bedrock during low sea level stand, followed by the formation of littoral and lagoon facies and defined coastal barrier-lagoon-estuary system during the post-glacial uppermost Pleistocene-lower Holocene eustatic rise of the sea level, and the upper Holocene high stand. GPR results show that Yudaitan, a sandy coastal bar backed by a low-laying land (shoal) just east of the active lagoon, is a continuous, parallel and slightly-wavy reflectors indicating homogeneous sandy or sandy gravel sediments, and inclined reflectors partly caused by progradation and accumulation of beach sand and gravel. Quasi-continuous, hummocky and chaotic reflectors from the shoal of Nangang village correspond to mixed accumulation of sands and clay. This research indicates the GPR is a non-intrusive, rapid, and economical method for high-resolution profiling of subsurface sediments in sandy gravelly coast.  相似文献   

塔里木盆地塔中32井中上奥陶统内潮汐沉积   总被引：11，自引：1，他引：11       下载免费PDF全文

何幼斌  高振中  张兴阳  翟永红  旷红伟 《古地理学报》2003,5(4):414-425

塔里木盆地塔中32井的中、上奥陶统钻遇厚度为1 462 m。它是一套巨厚的深灰色泥岩、页岩与灰色砂岩、粉砂岩互层夹少量灰岩的地层。其中深灰色泥岩、页岩最多；砂岩和粉砂岩主要分布于上部和下部，中部砂岩和粉砂岩较少；鲕粒灰岩数量少，主要夹于深灰色泥页岩中。这些砂岩和鲕粒灰岩既可单独成层，但更常见它们与深灰色泥页岩组合成薄互层。薄互层中发育脉状、波状和透镜状层理，并普遍发育交错层理和双向交错纹理。这些特征表明砂岩和鲕粒灰岩为深水斜坡上的内潮汐沉积的产物。这些内潮汐沉积进一步划分为4种类型：双向交错纹理细砂岩型、单向交错层和双向交错纹理中-细砂岩型、韵律性砂泥岩薄互层型和鲕粒灰岩型。它们具有5种垂向沉积层序，在剖面上常形成多旋回韵律性沉积组合。  相似文献   

底质不连续面类型、成因及遗迹学特征     

齐永安  徐华山 《地质科技情报》2003,22(1):41-46

底质不连续面是沉积作用中断时所形成的一种地层界面。根据底质的粘结程度可将底质不连续面划分为两大类：固底不连续面和硬底不连续面。固底不连续面中的简单停积面依靠沉积序列的变化来识别，界面上、下的生物地层带是连续的；而复成停积面上、下的生物地层带不连续。在硬底不连续面中，硬底的上、下地层属于同一个沉积体系，而继承性岩底的上、下地层则属于不同的沉积体系，其间发生过重大的沉积间断。根据底质控制的Glossifungites遗迹相和Trypanites遗迹相可以有效地识别各类不连续面并解释其成因。三种类型的不连续面具有层序地层学意义：①侵蚀性不连续面，包括低水位侵蚀面（LSE）和海进侵蚀面（TSE）；②无沉积间断面；③沉积性不连续面（凝缩段）。  相似文献   

The development of Nemurella pictetii Klapálek (Plecoptera: Nemouridae) in two springstreams in central Europe     

Andrei Nesterovitch  Peter Zwick   《Limnologica》2003,33(4):231-243

From April 1997 to June 1998 Nemurella pictetii populations were regularly sampled in two springstreams at 220 and 850 m a.s.l., respectively, in Hesse (Germany), at approximately 51°N. Random samples of larvae were taken at three week intervals during the vegetation period, and once a month during winter. Sex, instar, body length, head capsule width and wing pad length of all larvae were recorded. Temperatures were recorded every hour, temporal patterns of temperature agreed closely between sites. Mean winter lows were 3.9 °C at both sites, the mean summer high was 11.9 °C at the lower site, as opposed to 9.6 °C at the mountain site.At both sites, adult emergence started in May. At the mountain site, recruitment started in late July and continued into autumn. There was cohort splitting in the young generation. Some individuals grew rapidly until October–November, but last instar larvae first appeared in March the next year. 1600 degree-days above 0 °C were accumulated during complete development. At the lower site, recruitment began in early July, and cohort splitting also occurred. Fast growing summer recruits emerged as adults in late August, having accumulated only 700 degree-days (above 0 °C). Their offspring hatched in November-December and emerged the next spring, having accumulated also only 700 degree-days. However, only part of the population was bivoltine. Many of the summer recruits grew more slowly and accumulated close to 1900 degree days until they emerged the next spring, together with the offspring of their own fast-growing siblings. Dependence of growth rate on temperature could not be estimated and appears to vary with daylength. For example, 3–6 °C support growth and development provided daylength exceeds 10 hrs of light, or is rising.At both sites and in all cohorts individuals emerging earliest were larger than later emerging ones. The size decline is significantly correlated with number of days after the winter solstice. For the first time it is shown that the decline does not occur shortly before adult emergence but actually takes place several instars before the last. Size differences are then carried on, and amplified, during subsequent molts, until adulthood. The literature presently relates seasonal size declines of insects to high or rising temperatures experienced by larvae approaching adulthood. Our data show that, at least in Nemurella, this explanation fails. On average, females were distinctly larger than males. Differences in mean last instar size were noticed also between sites and years. They remain presently unexplained. The mean sex ratio in both populations was close to 1:1.  相似文献