我国西南周边地区夏秋季节降水变化及相应环流特征分析   总被引：1，自引：1，他引：0  

周秀华  肖子牛 《大气科学》2015,39(4):653-666

利用云南省124站观测资料及CRU(Climatic Research Unit)高分辨率降水数据分析了我国西南周边地区的降水时空变化特征, 并进一步对该地区夏、秋季节降水的周期、降水与季风活动的关系以及旱涝时期环流背景做出分析, 以探讨其年代际变化的可能影响机制。结果表明, 我国西南周边地区的降水空间分布随季节演变, 西南地区处于降水量相对小值区, 各季节降水量存在明显的年际变化以及年代际振荡特征。通过周期分析发现, 研究区域夏、季秋季降水均存在明显的年代际尺度周期, 近年来西南地区连续干旱很可能是由夏季和秋季的年代际尺度周期负位相配合造成, 并且降水的减少与夏季风活动偏弱、季风持续时间偏短有关。夏季秋季少雨时期与多雨时期环流场存在显著差异, 表现为少雨时期我国东部低层异常的偏北风, 青藏高原附近高层异常的反气旋型环流, 多雨时期则相反。  相似文献   

冬季华南准静止锋的结构和类型特征研究   总被引：4，自引：2，他引：2  

查书瑶  伊兰  赵平 《大气科学》2015,39(3):513-525

利用12年(2000～2011年)逐日的FNL(Final Operational Global Analysis)分析资料和逐日的中国站点降水资料, 定义了一个冬季华南准静止锋强度指数, 并根据该指数挑选出强准静止锋事件, 研究了强事件的结构特征、环流分型及其与降水的关系。结果表明:冬季强准静止锋事件多发于1、2月, 其发生频次在近12年里呈现明显上升趋势。强准静止锋锋区表现为等假相当位温线、等温线的密集带, 但是锋区湿度变化不明显, 并有明显逆温, 锋区由南北风辐合构成, 上升气流主要位于锋区上部, 纬向有两个次级环流与锋区相对应, 伴随正相对涡度和水汽通量辐合。根据850 hPa风场在锋区的辐合情况, 强准静止锋可分为北风辐合型、南北风辐合型、南风辐合型三种类型。在这三种类型中, 北风辐合型对应的北方冷空气最强, 华南降水最少;南风辐合型对应的南支槽最活跃, 华南降水最多;南北风辐合型介于两者之间。冬季华南准静止锋与冬季华南降水有一定相关, 在强准静止锋的背景下, 降水偏多时, 锋区低层的水汽通量辐合和上升运动偏强, 华南处于偏强南支槽前。  相似文献   

东亚夏季风异常活动的多模态特征:不同再分析资料的比较分析   总被引：2，自引：1，他引：1  

黄燕玲  陈海山  蒋薇  许蓓  李忠贤 《大气科学》2015,39(1):145-160

利用1979～2002年ERA-40、ERA interim、JRA-25和NCEP-DOE AMIP-Ⅱ(简称为NCEP-2)再分析资料,采用扩展经验正交分解(EEOF)、相关分析等方法,对比分析了不同资料所揭示的东亚夏季风异常活动的多模态特征,在此基础上探讨了东亚夏季风异常活动各模态对应的大气环流异常分布型及其与中国夏季降水的可能联系。结果表明:(1)四套再分析资料所揭示的东亚夏季风异常活动均存在三种差异显著的空间模态,且各套资料对东亚夏季风异常活动空间多模态特征具有很好的一致性,仅NCEP-2的结果与其他资料略有差异。(2)第一模态体现了夏季风年际异常在中国南方和北方的反相变化,并具有显著的3～6年和准8年周期;与正(负)时间系数相对应,850 hPa风场、500 hPa高度场、SLP均显示东亚沿岸存在从西北太平洋经过日本以南到达鄂霍次克海的“-+-”(“+-+”)经向三极型结构;相应的降水变化在长江中下游为显著的负(正)异常,而在我国东北东部、东南沿海及云南西部则为正(负)异常。(3)第二模态反映了夏季风活动主导模态的一致性变化且在1993年左右发生年代际转折,并呈现准12年周期的强弱交替分布。当对应的时间系数为正(负)时,850 hPa风场在环贝加尔湖地区受强大的异常反气旋(气旋)控制;500 hPa高度场上,中高纬地区表现为异常的纬向波列结构,具体表现为起源于欧洲大陆西部经西西伯利亚平原向东南方向延伸至东北亚地区的“+-+”(“-+-”)的波列;SLP在我国大陆主要为正(负)异常,东亚夏季风整体减弱(加强);对应的夏季降水异常场呈现“南涝北旱”(“南旱北涝”)的分布形势。(4)第三模态表明了夏季风异常活动的东西反相变化,且有12～16年的准周期变化。对应正(负)的时间系数,115°E 以东地区盛行异常偏南(北)风,而115°E 以西地区主要盛行异常偏北(南)风;500 hPa高度场、SLP均显示出东亚沿岸地区、鄂霍次克海至日本以南洋面的“-+”(“+-”)波列以及欧亚大陆北部的准纬向遥相关波列;夏季降水在我国大部分地区偏多(偏少),显著变化主要位于黄淮及附近地区。  相似文献   

冬季北太平洋流场异常主要模态与PDO及NPGO的关系   总被引：1，自引：0，他引：1  

吕庆平  卢姁  朱娟  戴文灏  张铭 《海洋学研究》2015,33(2):1-7

采用复经验正交函数(EOF)分解和小波分析,对冬季北太平洋上层海流异常进行了统计动力诊断,并讨论了主要模态与北太平洋年代际振荡(PDO)模态和北太平洋环流振荡(NPGO)模态的关系。结果显示,冬季北太平洋上层洋流异常复EOF分解的第一模态是PDO在流场异常上的反映,第二模态则包含了NPGO的明显信息。主要依据有:(1)第一和第二模态的实时间系数序列分别有准20a和准13a的年代际变化周期,与PDO和NPGO模态的年代际变化周期相同;(2)第一和第二模态实时间系数与北太平洋海表面温度异常(SSTA)的回归系数场的空间分布分别与PDO和NPGO模态的空间结构相近。根据第一和第二模态上层洋流异常计算得到的垂直运动异常的分布,与SSTA的PDO和NPGO模态的空间分布类似,表明海盆尺度流场异常造成的垂直运动是形成PDO和NPGO模态的重要原因。  相似文献   

新疆艾肯达坂物化探综合异常的再解释     

刘春涌  黄诚  黄启峰  张莉  陈兴贵 《新疆地质》2005,23(3):244-248

新疆和静县艾肯达坂39号铜矿点东南第四系大面积覆盖区存在1个物化探综合异常,多年来备受关注．2002年钻探查证后,对异常进行了再解释,查明了引起异常的原因．该高极化低电阻率激电异常是由下志留统依南里克组一套浅变质岩中的弱金矿化、弱石墨化、弱黄铁矿化碳质粉砂岩引起;低重力异常是由下志留统依南里克组中的次生石英岩、硅质岩和硅化大理岩引起;磁异常主要由厚达20m左右的下二叠统艾肯达坂组中基性火山岩砾石、岩块及碎屑等第四系堆积物引起,而下志留统依南里克组浅变质岩基本为无磁性岩石;全铜、有机铜和活动态铜异常主要是由第四系堆积物中大量铜矿转石和含铜高的中基性火山岩引起;壤中汞气和热释汞气异常是由断裂引起．证实了艾肯达坂物化探综合异常处于拉尔墩深大断裂带上．区域成矿地质条件对比表明,西南天山下志留统依南里克组一套浅变质岩具有形成“黑色岩系”型金矿的有利地质条件,是突破“库姆托尔式”金矿的有利地层,建议加强该区的金矿普查工作．  相似文献   

The circulation, water masses and sea-ice of Baffin Bay   总被引：2，自引：0，他引：2  

Charles C.L Tang  Charles K. Ross  Tom Yao  Brian Petrie  Brendan M. DeTracey  Ewa Dunlap 《Progress in Oceanography》2004,63(4):183-228

The oceanographic, meteorological and sea-ice conditions in Baffin Bay are studied using historical hydrographic, satellite and meteorological data, and a set of current meter data from a mooring program of the Bedford Institute of Oceanography. Baffin Bay is partially covered by sea-ice all year except August and September. The interannual variation of the ice extent is shown to be correlated with winter air temperature. Available hydrographic data were used to study the water masses and the horizontal and vertical distribution of temperature/salinity. Three water masses can be identified – Arctic Water in the upper 100–300 m of all regions except the southeast, West Greenland Intermediate Water at 300–800 m in most of the interior of Baffin Bay, and Deep Baffin Bay Water in all regions below 1200 m. The temperature and salinity in Baffin Bay have limited seasonal variability except in the upper 300 m of eastern Davis Strait, northern Baffin Bay and the mouth of Lancaster Sound. Summer data have a temperature minimum at 100 m, which suggests winter convection does not penetrate deeper than this depth. Current meter data and results of a circulation model indicate that the mean circulation is cyclonic. The seasonal variation of the currents is complex. Overall, summer and fall tend to have stronger currents than winter and spring at all depths. Among the different regions, the largest seasonal variation occurs at the mouth of Lancaster Sound and the Baffin Island slope. Model generated velocity fields show a basic agreement with the observed currents, and indicate strong topographic control in the vicinity of Davis Strait and on the Greenland shelves. The model also produces a southward counter current on the Greenland slope, which may explain the observed high horizontal shears over the Greenland slope. Estimates of the volume and fresh water transports through Lancaster, Jones and Smith Sounds are reviewed. Transports through Davis Strait are computed from the current meter data. The balance of freshwater budget and sensitivity of the thermohaline circulation to freshwater transport are discussed.  相似文献   

Three dimensional diagnostic, semidiagnostic and prognostic calculations of current in the East China Sea in April of 1994   总被引：3，自引：0，他引：3  

Wang Huiqun  Yuan Yaochu 《海洋学报(英文版)》2001,20(1):15-28

ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｒｅａｒｅｍａｎｙｍｏｄｅｌｓｔｏｃａｌｃｕｌａｔｅｔｈｅｃｕｒｒｅｎｔｓｉｎｔｈｅＥａｓｔＣｈｉｎａＳｅａａｎｄｏｔｈｅｒｎｅｉｇｈｂｏｒ ｉｎｇｓｅａｓ ,ａｎｄｓｏｍｅｏｆｔｈｅｍａｒｅｂｅｉｎｇｍｏｄｉｆｉｅｄａｎｄｄｅｖｅｌｏｐｅｄｗｉｔｈｔｈｅｔｉｍｅ .Ｔｈｅｓｅｍｏｄｅｌｓａｒｅａｓｆｏｌｌｏｗｓ :(1 )ｔｈｅｆｉｎｉｔｅｅｌｅｍｅｎｔｍｅｔｈｏｄ ,ａｎｄａｃｏｍｂｉｎａｔｉｏｎｏｆｆｉｎｉｔｅｅｌｅｍｅｎｔｍｅｔｈｏｄｗｉｔｈｔｈｅａｃｃｕｒａｔｅｓｏｌ…  相似文献   

The nearshore western Beaufort Sea ecosystem: Circulation and importance of terrestrial carbon in arctic coastal food webs   总被引：1，自引：0，他引：1  

Kenneth H. Dunton  Thomas Weingartner  Eddy C. Carmack   《Progress in Oceanography》2006,71(2-4):362

The nearshore shelf of the Beaufort Sea is defined by extreme physical and biological gradients that have a distinctive influence on its productivity and trophic structure. Massive freshwater discharge from the Mackenzie River, along with numerous smaller rivers and streams elsewhere along the coast, produce an environment that is decidedly estuarine in character, especially in late spring and summer. Consequently, the Beaufort coast provides a critical habitat for several species of amphidromous fishes, some of which are essential to the subsistence lifestyle of arctic native populations. Because of its low in situ productivity, allochthonous inputs of organic carbon, identifiable on the basis of isotopic composition, are important to the functioning of this arctic estuarine system. Coastal erosion and river discharge are largely responsible for introducing high concentrations of suspended sediment from upland regions into the nearshore zone. The depletion in the ¹³C content of invertebrate and vertebrate consumers, which drops about 4–5‰ eastward along the eastern Alaskan Beaufort Sea coast, may reflect the assimilation of this terrestrial organic matter into local food webs. In addition, the large range in ¹³C values of fauna collected in the eastern Beaufort (nearly 8‰) compared to the same species in the northeastern Chukchi (3‰), indicate a lower efficiency of carbon transfer between trophic levels in the eastern Beaufort. The wider spread in stable isotope values in the eastern Beaufort may also reflect a decoupling between benthic and pelagic components. Isotopic tracer studies of amphidromous fishes in the Simpson Island barrier island lagoon revealed that terrestrial (peat) carbon may contribute as much as 30–50% of their total dietary requirements. On the eastern Alaska Beaufort Sea coast, the δ¹³C values of arctic cod collected in semi-enclosed lagoons were more depleted, by 3–4‰, compared to fish collected in the coastal Beaufort Sea. Calculations from isotopic mixing equations indicate cod from lagoons may derive 70% of their carbon from terrestrial sources. The δ¹⁵N values of lagoon fish were also 4‰ lower than coastal specimens, reflective of the lower δ¹⁵N values of terrestrially derived nitrogen (0–1.5‰ compared to 5–7‰ for phytoplankton). The role of terrestrial carbon in arctic estuarine food webs is especially important in view of the current warming trend in the arctic environment and the role of advective processes that transport carbon along the nearshore shelf. Biogeochemical studies of the arctic coastal estuarine environment may provide more insights into the function of these biologically complex ecosystems.  相似文献   

Ocean Model Simulation of Southern Indian Ocean Surface Currents   总被引：1，自引：0，他引：1  

Anshu Prakash Mishra  S. Rai  A. C. Pandey 《Marine Geodesy》2007,30(4):345-354

The dynamic importance of the Southern Indian Ocean (SIO) lies in the fact that it connects the three major world oceans: the Pacific, Atlantic, and Indian Oceans. Modeling study has been used to understand the circulation pattern of this very important region. Simulation of SIO (10°N-60°S and 30°E-120°E) is performed with z-coordinate Ocean General Circulation Model (OGCM) viz; MOM3.0 and the results have been compared with observed ship drift data. It is found that except near coastal boundaries and in equatorial region, the simulated current reproduce most well known current pattern such as Antarctic Circumpolar Current (ACC), South Equatorial Current (SEC) etc. and bears a resemblance to that of the observed data; however the magnitude of the surface current is weaker in model than the observed data, which may be due to deficiency in the forcing field and boundary condition and problem with observed data. The annual mean wind stress curl computed over the oceanic domain reveals about ACC and its similar importance. The way in which the ocean responds to the windstress and vertically integrated transport using model output is fascinating and rather good.  相似文献   

东海和南黄海夏季环流的斜压模式   总被引：17，自引：6，他引：17  

王辉 《海洋与湖沼》1996,27(1):73-78

基于拉格朗日余流及其输运过程的一种三维空间弱非线性理论，引进了黑潮边界力及长江径流，给出了东海和南黄海的夏季环流及上升流区的分布。计算结果表明：在黑潮西侧存在着台湾－对马暖流系统；进入朝鲜海峡的对马暖流来自台湾暖流、黑潮、东海混合水和西朝鲜沿岸流；黄海暖流主要来源于东海混合水，表面有部分来自对马暖流；闽浙沿岸存在上升流区且构成一带状区域；在长江口外、东海东北部和陆坡上也存在在上升流式；陆坡处上升流  相似文献