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111.
Correction method for full-depth current velocity with lowered acoustic Doppler current profiler (LADCP) 总被引:1,自引:0,他引:1
A new method is presented to process and correct full-depth current velocity data obtained from a lowered acoustic Doppler
current profiler (LADCP). The analysis shows that, except near the surface, the echo intensity of a reflected sound pulse
is closely correlated with the magnitude of the difference in vertical shear of velocity between downcast and upcast, indicating
an error in velocity shear. The present method features the use of echo intensity for the correction of velocity shear. The
correction values are determined as to fit LADCP velocity to shipboard ADCP (SADCP) and LADCP bottom-tracked velocities. The
method is as follows. Initially, a profile of velocity relative to the sea surface is obtained by integrating vertical shears
of velocity after low-quality data are rejected. Second, the relative velocity is fitted to the velocity at 100–800 dbar measured
by SADCP to obtain an “absolute” velocity profile. Third, the velocity shear is corrected using the relationship between the
errors in velocity shears and echo intensity, in order to adjust the velocity at sea bottom to the bottom-tracked velocity
measured by LADCP. Finally, the velocity profile is obtained from the SADCP-fitted velocity at depths less than 800 dbar and
the corrected velocity shear at depths greater than 800 dbar. This method is valid for a full-depth LADCP cast throughout
which the echo intensity is relatively high (greater than 75 dB in the present analysis). Although the processed velocity
may include errors of 1–2 cm s−1, this method produced qualitatively good current structures in the Northeast Pacific Basin that were consistent with the
deep current structures inferred from silicate distribution, and the averaged velocities were significantly different from
those calculated by the Visbeck (2002) method. 相似文献
112.
Following our previous study (Sugimoto and Hanawa, 2005b), we further investigate the reason why reemergence of winter sea
surface temperature anomalies does not occur in the North Pacific eastern subtropical mode water (NPESTMW) area, despite its
occurrence in the North Pacific subtropical mode water and North Pacific central mode water areas. We use vertical temperature
and salinity profiles of the World Ocean Circulation Experiment Hydrographic Program and Argo floats with high vertical and
temporal resolution, together with heat flux data through the sea surface. We point out first that one of the causes for non-occurrence
of reemergence is that the thickness of NPESTMW is very thin. In addition to this basic cause, two major reasons are found:
a vigorous mixing in the lower portion of NPESTMW and less heat input from the atmosphere in the warming season. Since, in
the lower portion of NPESTMW and deeper, the stratification is favorable for salt-finger type convection to occur compared
with the other mode water areas, vigorous mixing takes place. This is confirmed by both a large Turner Angle there and the
existence of staircase structures in vertical temperature and salinity profiles. From the viewpoint of heat input, the NPESTMW
area gradually gains heat in the warming season compared with other mode water areas. As a result, NPESTMW cannot be capped
so quickly by the shallow summer mixed layer, and water properties of NPESTMW are to be gradually modified, even in the upper
portion. 相似文献
113.
热释光是矿物晶体接受环境核辐射作用后积蓄起来的能量在受到热激发时以光的形式释放出来的一种物理现象,它与晶体损伤、晶体中杂质混入等原因所导致的晶格缺陷有关.热释光强度的大小主要取决于自然界中长寿命放射性元素(238U,235U,230Th,40K及其子体)的衰变,与其他物理、化学、生物或人类活动无关.热释光特征能有效反映晶体形成的环境条件.热释光方法的制样简单、测量快捷,因此在辐射学、核工业、核医学、环境学、农业、考古学、地质学等领域都得到了广泛的应用.在陆地地质学上热释光方法在地质年代测定[1,2]、地层对比[3]、矿物世代划分[4]、矿床含矿评价[4,5]、陨石形成热的历史恢复[6]以及地质事件识别[7]等方面都取得了不少成果. 相似文献
114.
Abstract. Peyssonnelia bed distribution on continental shelf bottoms of the Balearic Islands (Western Mediterranean) ranges from 40 to 90 m depth. Different species of Peyssonnelia dominate these bottoms and, according to multivariate techniques, two main assemblages have been distinguished: the Peyssonnelia rosa-marina beds and the Peyssonnelia sp. beds, together with some transition samples between Peyssonnelia and maërl beds. Erect red algae are always abundant. Although average yearly irradiance reaching these beds is only 6.4-0.3% of subsurface irradiance, the species richness averages 45 species per sample (1600 cm2 ) and mean biomass is 2835 g dw. m-2 . The high carbonate content of the living algae of these bottoms suggests that they are important contributors to the production of sediments in the Balearic continental shelf. 相似文献
115.
Jean-Marie Auzende Eiichi Honza Xavier Boespflug Satendra Deo Jean-Philippe Eissen Jun Hashimoto Philippe Huchon Junichiro Ishibashi Yo Iwabuchi Philip Jarvis Masato Joshima Kiyoyuki Kisimoto Yasuto Kuwahara Yves Lafoy Tsuyoshi Matsumoto Jean-Pierre Maze Kiyohiko Mitsuzawa Hiroyasu Monma Takeshi Naganuma Yukihiro Nojiri Suguru Ohta Kiyoshi Otsuka Yoshihisa Okuda Hélène Ondreas Akira Otsuki Etienne Ruellan Myriam Sibuet Manabu Tanahashi Takeo Tanaka Tetsuro Urabe 《Marine Geophysical Researches》1990,12(4):269-283
The aim of the Japanese-French Kaiyo 87 cruise was the study of the spreading axis in the North Fiji Basin (SW Pacific). A
Seabeam and geophysical survey allowed us to define the detailed structure of the active NS spreading axis between 16° and
22° S and its relationships with the left lateral motion of the North Fiji Fracture Zone. Between 21° S and 18°10′ S, the
spreading axis trends NS. From 18°10 S to 16°40 S the orientation of the spreading axis changes from NS to 015°. North of
16°40′ S the spreading axis trends 160°. These two 015° and 160° branches converge with the left lateral North Fiji fracture
zone around 16°40′ S to define an RRFZ triple junction. Water sampling, dredging and photo TV deep towing give new information
concerning the hydrothermal activity along the spreading axis. The discovery of hydrothermal deposits associated with living
communities confirms this activity. 相似文献
116.
《Journal of Oceanography》2007,63(6):983-994
A mesoscale iron-enrichment study (SEEDS II) was carried out in the western subarctic Pacific in the summer of 2004. The iron
patch was traced for 26 days, which included observations of the development and the decline of the bloom by mapping with
sulfur hexafluoride. The experiment was conducted at almost the same location and the same season as SEEDS (previous iron-enrichment
experiment). However, the results were very different between SEEDS and SEEDS II. A high accumulation of phytoplankton biomass
(∼18 mg chl m−3) was characteristic of SEEDS. In contrast, in SEEDS II, the surface chlorophyll-a accumulation was lower, 0.8 to 2.48 mg m−3, with no prominent diatom bloom. Photosynthetic competence in terms of F
v/F
m for the total phytoplankton community in the surface waters increased after the iron enrichments and returned to the ambient
level by day 20. These results suggest that the photosynthetic physiology of the phytoplankton assemblage was improved by
the iron enrichments and returned to an iron-stressed condition during the declining phase of the bloom. Pico-phytoplankton
(<2 μm) became dominant in the chlorophyll-a size distribution after the bloom. We observed a nitrate drawdown of 3.8 μM in the patch (day 21), but there was no difference in silicic acid concentration between inside and outside the patch. Mesozooplankton
(copepod) biomass was three to five times higher during the bloom-development phase in SEEDS II than in SEEDS. The copepod
biomass increased exponentially. The grazing rate estimation indicates that the copepod grazing prevented the formation of
an extensive diatom bloom, which was observed in SEEDS, and led to the change to a pico-phytoplankton dominated community
towards the end of the experiment. 相似文献
117.
东太平洋柱状沉积物的古气候和古环境记录 总被引:1,自引:2,他引:1
太平洋深海盆地的远洋沉积物在物质组成和来源上远较大陆边缘简单.由于远离大陆,又有海沟与周边大陆分隔,太平洋深海沉积物中通常不包含由河流水系搬运而来的悬浮物,因此从深海沉积物中提取古气候、古环境信息可以避免诸多地质因素相互叠加和干扰[1].深海远洋沉积物中的主要组分是风成陆源碎屑(包括火山碎屑)和来自上层海水的生源组分(降落到洋底的生物壳体)以及由海解作用形成的自生矿物[2],其中陆源碎屑的相对含量、粒度及矿物成分可以反映大气环流的强度及物源区的气候环境[1],生源组分的组成、相对含量和丰度以及种属含量变化则与表层海水的生产力和溶解作用有关. 相似文献
118.
Spatial and temporal variability of heat content above the thermocline in the tropical Pacific Ocean 总被引:1,自引:0,他引:1
Abstract-Heat content of the upper layer above the 20℃ isotherm in the tropical Pacific Ocean isestimated by using the sea temperature data set with a resolution 2°latitude×5°longitude (1980~1993)for the water depths (every 10 m) from 0 m to 400 m, and its temporal and spatial variabilities are an-alyzed. (1) The temporal variability indicates that the total heat in the upper layer of the equatorial Pa-cific Ocean is charcterized by the interannual variability. The time series of the equatorial heat anomaly5 months lead that of the El Nino index at the best positive lag correlation between the two, and theformer 13 months lag behind the latter at their best negative lag correlation. Therefore the equatorialheat content can be used as a better predictor than the El Nino index for a warm or cold event. In addi-tion, it is also found that less heat anomaly in the equator corresponds to the stronger warm events inthe period (1980~1993) and much more heat was accumulated in the 4 years including 1992/1 相似文献
119.
利用RAPD和AFLP标记 ,以一回交家系 [(Miyagi×Hiroshima)×Miyagi]为作图群体 ,构建了太平洋牡蛎的遗传连锁图谱。用经过筛选的 3 3个RAPD引物和 1 1个AFLP引物组合 ,对父母本和 80个子代个体进行了遗传分析。共得到母本分离标记 1 93个 ,其中 1 44个符合1∶1孟德尔分离规律。父本分离标记 1 5 6个 ,其中 1 1 1个符合 1∶1孟德尔分离规律。雌性框架图包括 99个遗传标记 ,定位在 1 2个连锁群中 ,覆盖 985 2cM ,标记间平均间隔 1 1 3cM。另外有 3个三联体 ,7个连锁对 ,图谱共覆盖 1 1 6 5 7cM。雄性框架图包括 72个遗传标记 ,分布在 8个连锁群 ,覆盖 81 1cM ,标记间平均间隔 1 2 7cM。另外有 4个三联体 ,3个连锁对 ,图谱共覆盖93 1 8cM。 相似文献
120.