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991.
Abstract Detailed geologic examination of the Eocene accretionary complex (Hyuga Group) of the Shimanto terrane in southeastern Kyushu revealed that the oceanic plate was composed of Paleocene to Lower Eocene mudstone and siliceous mudstone, lower Middle Eocene red mudstone, and mid-Middle Eocene trench-fill turbidite with siltstone breccia, successively overlying the pre-Eocene oceanic plate. This oceanic plate sequence was overlain by Upper Eocene siltstone. Deposition of the lower Middle Eocene red mudstone was accompanied by basalt flows and it is interbedded with continental felsic tuff, which indicates that the basalt and red mudstone were deposited near the trench just before accretion. The Hyuga Group has very similar geological structure to that of the chert–clastic complexes found in the Jurassic accretionary complexes in Japan: that is, a decollement fault formed in the middle of an oceanic plate sequence, and an imbricate structure formed only in the upper part of the sequence. Thus, it appears that the Hyuga Group was formed by the same accretionary process as the Jurassic accretionary complexes. No accretion occurred before the Middle Eocene, and the rapid accretion of the Hyuga Group was commenced by the supply of coarse terrigenous sediments in the mid-Middle Eocene, when the direction of movement of the Pacific Plate changed. The pre-Eocene oceanic basement and lower Middle Eocene volcanic activity suggest that the oceanic plate partly preserved in the Hyuga Group was very similar to the northern part of the present West Philippine Sea Plate. 相似文献
992.
太平洋海温异常对大理雨季开始期的影响 总被引:1,自引:0,他引:1
采用大理州雨季开始期资料、1961年6月~2008年5月太平洋5°×5°共286个格点的逐月平均海温资料及NCEP/NCAR的SSTA资料,通过相关分析发现,太平洋海温与大理雨季开始期的关系密切,春季和上年秋季太平洋海温对大理雨季开始的影响较大。雨季开始前若发生厄尔尼诺事件,大理雨季开始期偏晚,反之,若发生拉尼娜事件,大理雨季开始期偏早。N ino3区的海温异常对大理雨季开始期的影响相当明显,当5月N ino3区的海温异常偏高时,大理雨季开始期偏晚;反之,当5月N ino3区的海温异常偏低时,大理雨季开始期偏早,N ino3区海温异常可以作为大理雨季开始期预测的一个强信号因子。 相似文献
993.
Using NCEP/NCAR reanalysis geopotential height (GHT) and wind at 850 hPa, GHT at 500 hPa, precipitation rate, sea level pressure
(SLP) and precipitation observations from more than 600 stations nationwide in June–August from 1951 to 2006, and focusing
on the East Asia-West Pacific region (10°–80°N, 70°–180°E), interannual variation of East Asian summer monsoon (EASM) and
its correlations with general circulation and precipitation patterns are studied by using statistical diagnostic methods such
as 9-point high pass filtering, empirical orthogonal function (EOF) analysis, composite analysis and other statistical diagnosis,
etc. It is concluded as follows: (1) EOF analysis of SLP in the East Asia-West Pacific region shows the existence of the zonal
dipole oscillation mode (APD) between the Mongolia depression and the West Pacific high, and APD index can be used as an intensity
index of EASM. (2) EOF analysis of GHT anomalies at 500 hPa in the East Asia-West Pacific region shows that the first EOF
mode is characterized with an obvious meridional East Asian pattern (EAP), and EAP index can also be used as an EASM intensity
index. (3) The composite analysis of high/low APD index years reveals the close correlation of APD index with EAP at 500 hPa
(or 850 hPa). The study shows an obvious opposite correlation exists between APD index and EAP index with a correlation coefficient
of −0.23, which passes the confidence test at 0.10 level. (4) Both APD and EAP indexes are closely correlated with precipitation
during flood-prone season in China and precipitation rate over the East Asia-West Pacific region. The significant correlation
area at 5% confidence level is mainly located from the southern area of the Yangtze River valley to the ocean around southern
Japan, and the former is a positive correlation and the latter is a negative one.
Foundation: Cooperative Project funded by the Ministry of Science and Technology of the People’s Republic of China, No.2007DFB20210;
National Natural Science Foundation of China, No.90502003; JICA China-Japan Technical Cooperative Project “China-Japanese
Cooperative Research Center on Meteorological Disasters”.
Author: Yu Shuqiu, Associate Professor, specialized in climate and climate change. 相似文献
994.
The influence of tropical Indian Ocean warming on the Southern Hemispheric stratospheric polar vortex 总被引:1,自引:0,他引:1
ShuangLin Li 《中国科学D辑(英文版)》2009,52(3):323-332
During the past decades, concurrent with global warming, most of global oceans, particularly the tropical Indian Ocean, have
become warmer. Meanwhile, the Southern Hemispheric stratospheric polar vortex (SPV) exhibits a deepening trend. Although previous
modeling studies reveal that radiative cooling effect of ozone depletion plays a dominant role in causing the deepening of
SPV, the simulated ozone-depletion-induced SPV deepening is stronger than the observed. This suggests that there must be other
factors canceling a fraction of the influence of the ozone depletion. Whether the tropical Indian Ocean warming (IOW) is such
a factor is unclear. This issue is addressed by conducting ensemble atmospheric general circulation model (AGCM) experiments.
And one idealized IOW with the amplitude as the observed is prescribed to force four AGCMs. The results show that the IOW
tends to warm the southern polar stratosphere, and thus weakens SPV in austral spring to summer. Hence, it offsets a fraction
of the effect of the ozone depletion. This implies that global warming will favor ozone recovery, since a warmer southern
polar stratosphere is un-beneficial for the formation of polar stratospheric clouds (PSCs), which is a key factor to ozone
depletion chemical reactions.
Supported by National Natural Science Foundation of China (Grant Nos. 40775053 and 90711004), National Basic Research Program
of China (Grant No. 2009CB421401), and Innovation Key Program of Chinese Academy of Sciences (Grant Nos. KZCXZ-YW-Q11-03,
KZCZ2-YW-Q03-08) 相似文献
995.
Xuan Ding LianFeng Gao NianQiao Fang WenJun Qu Jian Liu JiangShan Li 《中国科学D辑(英文版)》2009,52(8):1091-1103
Base on the Os isotope stratigraphy together with the empirical growth rate models using Co concentrations, the growth ages
of the ferromanganese crusts MHD79 and MP3D10 distributed in the seamount of Pacific are confirmed. Through the contrast and
research on the previous achievements including ODP Leg 144 and the crusts CD29-2, N5E-06 and N1–15 of the seamount of the
Central Pacific, the uniform five growth and growth hiatus periods of them are found, and closely related to the Cenozoic
ocean evolvement process. In the Paleocene Carbon Isotope Maximum (PCIM), the rise of the global ocean productivity promoted
the growth of the seamount crust; the first growth hiatus (I) of the ferromanganese crust finished. In the Paleocene-Eocene
Thermal Maximum (PETM), though the vertical exchange of seawater was weakened, the strong terrestrial chemical weathering
led to the input of a great amount of the terrigenous nutrients, which made the bioproductivity rise, so there were no crust
hiatuses. During 52–50 Ma, the Early Eocene Optimum Climate (EECO), the two poles were warm, the latitudinal temperature gradient
was small, the wind-driven sea circulation and upwelling activity were weak, the terrestrial weathering was also weakened,
the open ocean bioproductivity decreased, and the ferromanganese crust had growth hiatus again (II). From early Middle Eocene-Late
Eocene, Oligocene, it was a long-term gradually cooling process, the strengthening of the sea circulation and upwelling led
to a rise of bioproductivity, and increase of the content of the hydrogenous element Fe, Mn and Co and the biogenous element
Cu, Zn, so that was the most favorable stage for the growth of ferromanganese crust (growth periods III and IV) in the studied
area. The hiatus III corresponded with the Eocene- Oligocene boundary, is inferred to relate with the global climate transformation,
celestial body impact event in the Eocene-Oligocene transition. From the early to the middle Miocene, a large-scale growth
hiatus (hiatus period IV) of the ferromanganese crust in the studied area is inferred to relate with temporary warm up climate
and ephemeral withdrawal of Antarctic bottom water in the early Miocene. After that, the Antarctic ice sheets extended, the
bottom water circumfluence strengthened, the ocean fertility increased, and the once interrupted crust continued to grow in
the late Miocene (growth period V).
Supported by China Ocean Mineral Resources Research and Development Association “10th Five Year” Topic (Grant No. DY105-01-04-14) 相似文献
996.
997.
利用1992~2001年Topex/Poseidon卫星高度计遥感资料分析了太平洋东南海域 (5°~55°S ,70°~110°W)海面高度的季节及年际变化特征。研究结果表明 ,海区海面高度的季节变化总体上受太阳辐射季节变化的影响 ,南半球夏季 (1~3月 )和秋季 (4~6月 )大致为正距平 ,而冬季 (7~9月 )和春季 (10~12月 )大致为负距平 ,1996~1998年除外 ;同时 ,受季节性风场、海区罗斯贝波等的影响 ,海面高度变化的区域特征性很强。海面高度的年际变化在低纬处和沿岸还受ElNino影响。 相似文献
998.
Projections of ocean climate for northwestern Pacific Ocean 总被引:1,自引:1,他引:0
The long-term adjustment processes of atmosphere and ocean in response to gradually increased atmospheric CO2 concentration have been analyzed in 70 and 140a integrations with NCAR fully-coupled climate system model (CSM). In these experiments the CO2 concentration has been increased to double and quadruples the initial concentration, respectively. After 70a, at the time of CO2 doubling, the model predicts surface air temperature rises by 1.2 and 1.5K for the globe and the northwestern Pacific Ocean, respectively. The behavior of the quadrupling run is similar: each global and regional mean surface air temperatures increase by 2.8 and 3.0K at the time of CO2 quadrupling. From the experiments, surface air temperature changes in the northwestern Pacific Ocean will be more distinctive compared with the global average, mainly due to exceptionally large warming and sea level change near the entrance of the Kuroshio extension. 相似文献
999.
1000.