近42年西藏高原雅鲁藏布江中游夏季气候趋势和突变分析   总被引：32，自引：10，他引：32  

周顺武  假拉  杜军 《高原气象》2001,20(1):71-75

根据1957－1998年雅鲁藏布江中游拉萨、日喀则、泽当、江孜4个站6－8月的平均气温、降水资料，通过线性趋势估计和多项式函数拟合等方法分析了雅鲁藏布江中游地区夏季气候长期趋势变化和周期变化，并利用滑动T检验等方法讨论了突变的问题。结果表明：在过去42a里，该流域夏季气温有明显的上升趋势，1980年突变增暖非常明显；而夏季降水呈下降趋势，60年代中后期至80年代末降水普遍偏少，90年代降水出现回升势头。气温、降水的主要周期集中在高频波段，显著周期为2．8－3．5a。  相似文献   

气候变化对滦河流域水资源影响的水文模式模拟(Ⅰ)降水径流模式系统（PRMS）介绍及其在滦河流域的移植   总被引：1，自引：4，他引：1  

范广洲  吕世华  程国栋 《高原气象》2001,20(2):173-179

简单介绍了引进美国地质勘查中心发展的降水径流模式系统（PRMS）。认为PRMS模式具有多种模拟功能，包含的物理过程也较全面，是当前世界上较好的水文学模式。将PRMS模式系统移植到滦河流域，并对其模拟能力进行了初步检验。结果表明，模式系统在我国滦河流域的移植比较成功，而且能够较真实地再现滦河流域河川径流量及水资源其它分量的年际及季节变化，也可以用于研究气候变化对滦河流域水资源的影响。  相似文献   

论珠江三角洲与外围地区的互补性   总被引：5，自引：0，他引：5  

吕拉昌 《热带地理》2002,22(2):161-165

互补性是珠三角洲与外围地区实现共同发展的重要基础。文中从资源、产业及商品交流的角度，全面分析了珠江三角洲与外围地区的互补性关系，并指出要充分利用这种互补性关系，加强区域要素的交流与合作，走区域整合的发展道路。  相似文献   

4599858 Ocean wave energy device     

Joseph P. La Stella  Michael G. Tornabene 《Ocean Engineering》1987,14(1)

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Comments on “Floating Pontoon Breakwaters” by A.N. Williams, H.S. Lee and Z. Huang, Ocean Engineering 27 (2000) 221–240     

P. A. A. Laura  C. A. Rossit  S. La Malfa 《Ocean Engineering》2001,28(3):345

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Statistical characterization of active sonar reverberation using extreme value theory   总被引：1，自引：0，他引：1  

La Cour  B.R. 《Oceanic Engineering, IEEE Journal of》2004,29(2):310-316

The statistics of reverberation in active sonar are characterized by non-Rayleigh distributed amplitudes in the normalized matched filter output. Unaccounted for, this property can lead to high false-alarm rates in fixed-threshold detectors. A new approach to modeling threshold-crossing statistics based on extreme value theory is proposed, which uses the generalized Pareto distribution as the unique asymptotic model of the tail distribution, valid at large thresholds. Methods of parameter estimation are discussed and applied to active sonar reverberation collected on a hull-mounted sonar system. The statistics of reverberation in active sonar are found to generally have a power-law behavior in the tails with a shape parameter that is persistent in time and bandwidth dependent. The threshold needed for accurate parameter estimation is generally found to be well below that of typical fixed-threshold detectors.  相似文献   

Influence of atmospheric inputs on the iron distribution in the subtropical North-East Atlantic Ocean   总被引：3，自引：0，他引：3  

Graldine Sarthou  Alex R. Baker  Jurjen Kramer  Patrick Laan  Agathe Laës  Simon Ussher  Eric P. Achterberg  Hein J.W. de Baar  Klaas R. Timmermans  Stphane Blain 《Marine Chemistry》2007,104(3-4):186-202

Aerosol (soluble and total) iron and water-column dissolved (DFe, < 0.2 μm) and total dissolvable (TDFe, unfiltered) iron concentrations were determined in the Canary Basin and along a transect towards the Strait of Gibraltar, in order to sample across the Saharan dust plume. Cumulative dust deposition fluxes estimated from direct aerosol sampling during our one-month cruise are representative of the estimated deposition fluxes based on near surface water dissolved aluminium concentrations measured on board. Iron inventories in near surface waters combined with flux estimates confirmed the relatively short residence time of DFe in waters influenced by the Saharan dust plume (6–14 months). Enhanced near surface water concentrations of DFe (5.90–6.99 nM) were observed at the Strait of Gibraltar mainly due to inputs from metal-rich rivers. In the Canary Basin and the transect towards Gibraltar, DFe concentrations (0.07–0.76 nM) were typical of concentrations observed in the surface North Atlantic Waters, with the highest concentrations associated with higher atmospheric inputs in the Canary Basin. Depth profiles showed that DFe and TDFe were influenced by atmospheric inputs in this area with an accumulation of aeolian Fe in the surface waters. The sub-surface minimum of both DFe and TDFe suggests that a simple partitioning between dissolved and particulate Fe is not obvious there and that export may occur for both phases. At depths of around 1000–1300 m, both regeneration and Meddies may explain the observed maximum. Our data suggest that, in deep waters, higher particle concentrations likely due to dust storms may increase the scavenging flux and thus decrease DFe concentrations in deep waters.  相似文献   

Ecological implications of biomass and morphotype variations of bacterioplankton: an example in a coastal zone of the Northern Adriatic Sea (Mediterranean)   总被引：1，自引：0，他引：1  

Rosabruna La Ferla  & Marcella Leonardi 《Marine Ecology》2005,26(2):82-88

This study had the objective of quantifying the variability in abundance, cell volume, morphology and C content of a natural bacterioplankton community in a coastal zone of the North Adriatic Sea during two periods (February and June) of two consequent years (1996 and 1997). We used epifluorescence microscopy with Acridine Orange staining procedures and a microphotographic technique. Low variability in bacterial abundance (range 0.3–3.1 × 10⁵ cells ml^?1) occurred between summer and winter periods. Conversely, the cell volume and the calculated carbon content changed greatly with warm and cold periods (ranges: 0.015–0.303 μm³ and 5.83–42.17 fg C cell^?1, respectively). Elongated bacteria were dominant while coccoid cells prevailed only in February 1997. Biomass showed high variability (range 0.12–10.21 μg C l^?1) whilst the abundance did not show noticeable differences among the sampling periods. As a consequence, quantification of bacterial biomass based solely on cell abundance must be considered with caution because the true biomass could depend on variability in cell volumes and morphotypes.  相似文献   

Analytical and experimental investigation on transverse vibrations of solid, circular and annular plates carrying a concentrated mass at an arbitrary position with marine applications     

D.V. Bambill  S. La Malfa  C.A. Rossit  P.A.A. Laura 《Ocean Engineering》2004,31(2):127-138

This investigation arose from the practical necessity of placing a centrifugal pump rigidly attached to a thin, circular cover plate of a water tank in a medium size ocean vessel. Due to lack of space, it was necessary to locate the system off—center of the circular configuration. It was considered necessary to calculate the fundamental frequency of the coupled system.The first part of the present study is concerned with the determination of the fundamental frequency of vibration of a circular plate carrying a concentrated mass at an arbitrary position, using a variational approach.Numerical results are obtained for the stated problem for several combinations of the intervening geometric and mechanical parameters.An experimental investigation is also performed in the case of clamped plates.Based on the results for solid circular plates, the fundamental frequency of annular plates with a free inner edge and a concentrated mass is also obtained.Circular plates are fundamental structural elements in ocean engineering applications: from off-shore platforms to underwater acoustic transducers. In a great variety of circumstances, they must carry operational systems in an eccentric fashion. Since the dynamic performance is always of interest, one must know at least some of the basic dynamic parameters.  相似文献   

Bibliografia vulcanologica española     

Maximino San Miguel De La Cámara 《Bulletin of Volcanology》1952,12(1):203-214

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