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91.
92.
Channels of cross - equatorial flow and their characteristics Winds at every 5 deg. grid point from 30°E to 180° over the equator at 850 hPa and 200hPa from December 1984 to February 1985 have been separated into U(zonal wind) andV(meridional wind).The V component has been used to represent cross- equatorial flow. FromFig. 1 we obtained that as during the Northern summer,there are also severa1 regions in which 相似文献
93.
1990年7~8月,舟山地区的对虾养殖场暴发了流行性对虾黑鳃褐斑综合症,造成对虾大量死亡。作者根据这一病情,对病虾的主要器官组织进行了电镜观察。结果发现,病虾鳃丝细胞中有支原体感染。寄生部位为鳃呼吸上皮细胞的细胞质和核周腔。支原体多形态,呈近圆形、细长条形不等,无细胞壁,仅有单一膜包围,中心为一电子密度较低的区域。 相似文献
94.
Euniphysa, originally a genus of the family Eunicidae, was erected by Wesenberg-Lund in 1949, and for a longtime there has been only one species in this genus. The present report is based on our samples collected from the South China Sea, and we consider that the differences between Euniphysa and Eunice are very significant: Five occipital tentacles distributed unequidistantly; the jaw consists of 6 pairs of maxillary plates; the body may be divided into anterior region and posterior region, etc. Therefore we suggest that Euniphysa should be separated from Eunicidae, and become a new family Euniphysi-dae. At present this family includes 3 genera, namely, Euniphysa , Paraeuniphysa and 1 new genira Heterophysa; Totally there are 7 species, including 3 new species and 1 new combination species. 相似文献
95.
For convenience of dynamic analysis, some offshore structures such as fixed-type platforms are often modeled as the wedge beams supporting tip lumped masses. It is well-known that, due to the effect of the surrounding water, the natural frequencies of a beam in air (or dry beam) are different from those of the same beam immersed in water (or wet beam). However, if the natural frequencies and the associated mode shapes of a dry beam are calculated by taking account of the “added mass” for the immersed beam, then the last natural frequencies and mode shapes will be equal to the corresponding ones of the wet beam. Based on the last concept, the closed form solutions for natural frequencies and the associated mode shapes of the dry beam were determined first, then the partial differential equation of motion for the wet beam was transformed into a matrix equation by using the expansion theorem and the foregoing closed form solutions of free vibration responses for the dry beam. Solving the last matrix equation will give the required natural frequencies and the associated mode shapes of the wet beam. The formulation of this paper is available for the fully or partially immersed double tapered beams with either circular, square or rectangular cross-sections. The taper ratio for width and that for depth may be equal or unequal. The numerical results of this paper were compared with the existing results or the finite-element-method results and good agreement was achieved. 相似文献
96.
Temperature data at different layers of the past 45 years were studied and we found adiploe mode in the thermocline layer (DMT): anomalously cold sea temperature off the coast of Sumatra and warm sea temperature in the western Indian Ocean. First, we analyzed the temperature and the temperature anomaly (TA) along the equatorial Indian Ocean in different layers. This shows that stronger cold and warm TA signals appeared at subsurface than at the surface in the tropical Indian O-cean. This result shows that there may be a strong dipole mode pattern in the subsurface tropical Indian Ocean. Secondly we used Empirical Orthogonal Functions (EOF) to analyze the TA at thermocline layer. The first EOF pattern was a dipole mode pattern. Finally we analyzed the correlations between DMT and surface tropical dipole mode (SDM), DMT and Nino 3 SSTA, etc. and these correlations are strong. 相似文献
97.
众所周知,ENSO(El Nino/ Southern Oscillation)是发生在热带太平洋的年际时间尺度上最强的气候信号,与 El Nino (La Nina)相应的正(负)海温距平(SSTA)主要分布于赤道中东太平洋地区(Rasmusson et al.,1982)。相对于热带太平洋的年际ENSO现象,人们注意到北太平洋海平面气压(SLP)存在更长周期的年代际变化(Trenberth et al.,1994),有人认为这与北太平洋的表层温度(SST)变化有关(Latif et al.,1994),也有人认为与热带SST的异常关系更为密切(Jacobs et al.,1994)。20世纪80年代后的ENSO事件和20世纪60,70年代有明显的差别(Wang,1995),20世纪90年后El Nino发生频数增加,并且在1997和1998年出现了20世纪最强的一次Nino事件(McPhaden,1999)。
因此,不论是作为大气年代际变化可能的一个驱动因子,还是作为年际ENSO的背景场,从整体上了解太平洋SST的年代际时间尺度上的时、空变化特征都是十分重要的。 相似文献
98.
Quantity, timing, duration, and fluctuation of freshwater inflow are important factors affecting the development and health of aquatic and adjacent wetland ecosystems in coastal estuaries. This study assessed six decades of freshwater inflow from the Amite River, Tickfaw River, and Tangipahoa River watersheds to Lake Pontchartrain, a large oligohaline estuary in the Northern Gulf of Mexico, whose flood waters caused recent damage to the city of New Orleans in the aftermath of Hurricane Katrina. By utilizing the long-term (1940–2002) river discharge and climatic data from the three major tributary watersheds, monthly and annual freshwater inflows have been quantified and their spatial and temporal variations have been analyzed. On average, the three rivers discharged (±standard error) 0.27 ± 0.04 km3 freshwater monthly and 3.29 ± 0.15 km3 freshwater annually into the lake estuarine system, with the highest inflow from the Amite River (0.16 ± 0.03 m3 mon−1, and 1.91 ± 0.09 km3 yr−1) and the lowest inflow from the Tickfaw River (0.03 ± 0.00 km3 mon−1, and 0.34 ± 0.02 km3 yr−1). A distinct seasonality was evident with over 69% of the total annual inflow occurring during December and May (wet months) and with a low flow period from August to November (dry months). The monthly inflow during the wet months was positively correlated with the monthly precipitation (r2 = 0.64), while the monthly inflow during the dry months was subject to evapotranspiration. Furthermore, the study found a 20-year low flow period from 1954–1973 (2.76 ± 0.24 km3 yr−1) and a 24-year high flow period from 1975–1998 (3.84 ± 0.24 km3 yr−1), coinciding with both the climate variation and population growth in the watersheds. 相似文献
99.
A submerged apparatus, which consists of a buoy, several horizontal contraction and expansion tubes (Venturi-type tubes) and a long pipe, is expected to be used to pump the subsurface sea-water (200–300 meter depth) containing abundant nutrients to surface layer (50–100 m) by the dynamic of ocean currents. i.e. an artificial upwelling without energy cost. A preliminary experiment and analysis are undertaken and shows that the capacity of pumping the nutrient-rich sea-water is worth to build a pilot prototype model. 相似文献
100.
根据Taylor的湍流扩散理论和Hay、Pasquill提出的拉格朗日流和欧拉流的相关函数的相似性,用黄河三角洲埕北海域的实测资料,按四种不同方案计算出该海域的水平扩散系数和谱密度分布。指出:该海区潮流扩散系数主要受潮流的影响,其分布特征与潮流的分布基本一致,所求的水平扩散系数主要是由周期性的潮运动给予潮流扰动所致。方案4是通过富氏变换滤波消去了周期性潮流扰动,本方案计算的水平扩散系数是由周期为6h以下的小尺度涡提供能量。 相似文献