共查询到20条相似文献,搜索用时 15 毫秒
1.
WEI EnBo & LIU Ye Institute of Oceanology Chinese Academy of Sciences Qingdao China Graduate University of the Chinese Academy of Sciences Beijing China 《中国科学D辑(英文版)》2007,50(3):474-480
Based on the effective medium approximation theory of composites, the empirical model proposed by Pandey and Kakar is remedied to investigate the microwave emissivity of sea surface under wave breaking driven by strong wind. In the improved model, the effects of seawater bubbles, droplets and difference in temperature of air and sea interface (DTAS) on the emissivity of sea surface covered by whitecaps are discussed. The model results indicate that the effective emissivity of sea surface in-creases with DTAS increasing, and the impacts of bubble structures and thickness of whitecaps layer on the emissivity are included in the model by introducing the effective dielectric constant of whitecaps layer. Moreover, a good agreement is obtained by comparing the model results with the Rose’s ex-perimental data. 相似文献
2.
In the region southeast of Okinawa, during May to July 2001, a cyclonic and an anticyclonic eddy were observed from combined measurements of hydrocasts, an upward-looking moored acoustic Doppler current profiler (MADCP), pressure-recording inverted echo sounders (PIESs), satellite altimetry, and a coastal tide gauge. The hydrographic data showed that the lowest/highest temperature (T) and salinity (S) anomalies from a 13-year mean for the same season were respectively -3.0/ 2.5℃ and -0.20/ 0.15 psu at 380/500 dbar for the cyclonic/anticyclonic eddies. From the PIES data, using a gravest empirical mode method, we estimated time-varying surface dynamic height (D) anomaly referred to 2000 dbar changing from -20 to 30 cm, and time-varying T and S anomalies at 500 dbar ranging through about ±2 ℃ and ±0.2 psu, respectively. The passage of the eddies caused variations of both satellite-measured sea surface height anomaly (SSHA) and tide-gauge-measured sea level anomaly to change from about –20 to 30 cm, consistent with the D anomaly from the PIESs. Bottom pressure sensors measured no variation related to these eddy activities, which indicated that the two eddies were dominated by baro-clinicity. Time series of SSHA map confirmed that the two eddies, originating from the North Pacific Subtropical Countercurrent region near 20°―30°N and 150°―160°E, traveled about 3000 km for about 18 months with mean westward propagation speed of about 6 cm/s, before arriving at the region southeast of Okinawa Island. 相似文献
3.
Characteristics of shallow gas hydrate in Okhotsk Sea 总被引:1,自引:0,他引:1
LUAN XiWu JIN YoungKeun Anatoly OBZHIROV YUE BaoJing Key Lab of Marine Geology Environment Institute of Oceanology Chinese Academy of Sciences Qingdao China Korea Polar Research Institute KORDI Incheon - Korea V.I. Il’ichev Pacific Oceanological Institute of the Far Eastern Branch of Russian Academy of Sciences Vladivostok Russia 《中国科学D辑(英文版)》2008,51(3):415-421
Multidisciplinary field investigations were carried out in Okhotsk Sea by R/V Akademik M.A. Lavrentyev (LV) of the Russian Academy of Sciences (RAS) in May 2006, supported by funding agencies from Ko- rea, Russia, Japan and China. Geophysical data including echo-sounder, bottom profile, side-scan- sonar, and gravity core sample were obtained aimed to understand the characteristics and formation mechanism of shallow gas hydrates. Based on the geophysical data, we found that the methane flare detected by echo-sounder was the evidence of free gas in the sediment, while the dome structure de- tected by side-scan sonar and bottom profile was the root of gas venting. Gas hydrate retrieved from core on top of the dome structure which was interbedded as thin lamination or lenses with thickness varying from a few millimeters to 3 cm. Gas hydrate content in hydrate-bearing intervals visually amounted to 5%―30% of the sediment volume. This paper argued that gases in the sediment core were not all from gas hydrate decomposition during the gravity core lifting process, free gases must existed in the gas hydrate stability zone, and tectonic structure like dome structure in this paper was free gas central, gas hydrate formed only when gases over-saturated in this gas central, away from these struc- tures, gas hydrate could not form due to low gas concentration. 相似文献
4.
The formation and development environment of the “old red sands” on South China coasts is discussed according to the investigation
in the field and laboratory works. The authors believed that the “old red sands” are the aeolian sediments deposits in the
last glacial period of late Pleistocene when the sea level was lower than the present, and the laterization took place under
the hot and wet climate during the later interglacial and postglacial periods when the sea level was relatively high.
Project supported by the National Natural Science Foundation of China (Grant No. 49671012) 相似文献
5.
本文介绍一种由EM31-ICE型电磁感应仪和激光测距仪组合而成的船载电磁感应海冰厚度探测系统. 针对海冰和海水的电学特征,运用电磁感应技术提取探测系统至海冰下底面的距离,运用激光测距仪测量冰面粗糙度和探测系统至海冰上表面的距离,两组数据结合,实现了海冰厚度的探测. 通过南极现场探测数据分析,并与钻孔实测冰厚数据对比研究,定量分析了探测系统距离冰面的高度效应,建立了该系统冰厚测定值随高度变化的修正关系式,并对船载航行数据进行了系统校正. 与SCAR ASPeCt的冰厚数据对比分析,表明该系统能够获得可靠的海冰厚度并具有较高的精度,且能满足对极区大范围海冰厚度观测的需求. 相似文献
6.
Experimental observation of the nano-scale particles in geogas matters and its geological significance 总被引:2,自引:0,他引:2
The geogas collectors showing a geogas anomaly in field geogas prospecting and in simulation tests were selected for the observation
under high resolution microscopy. The result demonstrates that the geogas matter is transported in the form of nano-scale
particles with a size of aboutN nm to N-10 nm, and accumulated into aggregations of 1-2 μm to N.10 μm, with globular and film shape, and the component of
Cu, Zn, Cr, Au, Al, V, Si, Br, C1, S, Ca, etc. Based on the knowledge of nano science and technique, the mechanism of the
geogas prospecting and its significance in geology and mineral prospecting are discussed.
Project supported by the National Natural Science Foundation of China (Grant No. 49673202) and the Department of Science and
Technology of MGMR, PRC (Grant No. 9505201-1) 相似文献
7.
Wu WenBin Yang Peng Meng ChaoYing Shibasaki Ryosuke Zhou QingBo Tang HuaJun Shi Yun 《中国科学D辑(英文版)》2008,51(3):370-379
Dynamics of land use systems have attracted much attention from scientists around the world due to their ecological and socio-economic implications. An integrated model to dynamically simulate future changes in sown areas of four major crops (rice, maize, wheat and soybean) on a global scale is pre- sented. To do so, a crop choice model was developed on the basis of Multinomial Logit (Logit) model to model land users' decisions on crop choices among a set of available alternatives with using a crop utility function. A GIS-based Environmental Policy Integrated Climate (EPIC) model was adopted to simulate the crop yields under a given geophysical environment and farming management conditions, while the International Food Policy and Agricultural Simulation (IFPSIM) model was utilized to estimate crop price in the international market. The crop choice model was linked with the GIS-based EPIC model and the IFPSIM model through data exchange. This integrated model was then validated against the FAO statistical data in 2001-2003 and the Moderate Resolution Imaging Spectroradiometer (MODIS) global land cover product in 2001. Both validation approaches indicated reliability of the model for ad- dressing the dynamics in agricultural land use and its capability for long-term scenario analysis. Finally, the model application was designed to run over a time period of 30 a, taking the year 2000 as baseline. The model outcomes can help understand and explain the causes, locations and consequences of land use changes, and provide support for land use planning and policy making. 相似文献
8.
Mangshan loess on China’ s Central Plain and its response to tectonic movement and climate* 总被引:1,自引:0,他引:1
The Mangshan loess on China’s Central Plain, located on the transitional zone between the uplifting Loess Plateau and the
subsiding North China Plain, is a proximal sandy loess transported from the fanhead of alluvial fan in the lower reaches of
the Yellow River and has recorded the coupling effect of the tectonics and climate over the last 200 ka. An abrupt environmental
change indicated by the abrupt rise of deposit rate in the late penultimate glaciation, about 150 ka BP, took place; that
is, the Yellow River downcut and moved eastwards through the Sanmenxia Gorge and transported abundant materials from the Loess
Plateau to form paleosol S1 with a thickness of 15.7 m and loess L1 with a thickness of 77.3 m. The loess-paleosol sequence
at Mangshan has not only recorded detailed climate responses of this area to the East Asian monsoon, but also reflects the
tectonogenetic environmental effect caused by the trunk stream of the Yellow River cutting through Sanmenxia Gorge into sea.
Project supported by the National Natural Science Foundation of China (Grant No..49572132). 相似文献
9.
Zheng Wenzhong Ji Jing 《地震工程与工程振动(英文版)》2008,7(2):137-146
Tests of nine angle-steel concrete column (ASCC) specimens under low cyclic loading are described in a companion paper (Zheng and Ji, 2008). In this paper, the skeleton curves from the numerical simulation are presented, and show good agreement with the test results. Furthermore, parametric studies are conducted to explore the influence of factors such as the axial compression ratio, shear steel plate ratio, steel ratio, prismatic concrete compression strength, yield strength of angle steel and shear span ratio, etc., on the monotonic load-displacement curves of the ASCCs. Based on a statistical analysis of the calculated results, hysteretic models for load-displacement and moment-curvature are proposed, which agree well with the test results. Finally, some suggestions concerning the conformation of ASCCs are proposed, which could be useful in engineering practice. 相似文献
10.
The proper orthogonal decomposition (POD) method is used to construct a set of basis functions for spanning the ensemble of
data in a certain least squares optimal sense. Compared with the singular value decomposition (SVD), the POD basis functions
can capture more energy in the forecast ensemble space and can represent its spatial structure and temporal evolution more
effectively. After the analysis variables are expressed by a truncated expansion of the POD basis vectors in the ensemble
space, the control variables appear explicitly in the cost function, so that the adjoint model, which is used to derive the
gradient of the cost function with respect to the control variables, is no longer needed. The application of this new technique
significantly simplifies the data assimilation process. Several assimilation experiments show that this POD-based explicit
four-dimensional variational data assimilation method performs much better than the usual ensemble Kalman filter method on
both enhancing the assimilation precision and reducing the computation cost. It is also better than the SVD-based explicit
four-dimensional assimilation method, especially when the forecast model is not perfect and the forecast error comes from
both the noise of the initial filed and the uncertainty of the forecast model.
Supported by the National Natural Science Foundation of China (Grant No. 40705035), National High Technology Research and
Development Program of China (Grant No. 2007AA12Z144), Knowledge Innovation Project of Chinese Academy of Sciences (Grant
Nos. KZCX2-YW-217 and KZCX2-YW-126-2), and National Basic Research Program of China (Grant No. 2005CB321704) 相似文献
11.
We investigate helicopter electromagnetic (HEM) inversion schemes applied to synthetic and measured HEM sea ice profiling data. Direct HEM data-to-ice-thickness inversion is compared to three different formal, least squares layered earth inversion algorithms.By making several approximations, it is possible to directly invert a single channel measurement (i.e., the in-phase or quadrature component of a single frequency measurement) to obtain an estimate of sea ice thickness. Measurements from multiple input channels, however, can be used in a layered earth inversion to simultaneously recover several model parameters such as sea ice thickness, sea ice conductivity and sub-ice bathymetry. Synthetic data sets for a particular two-frequency HEM system showed that simple least squares inversion algorithms produce reliable estimates of sea ice thickness in cases where the ice is thicker than 3 m. These methods could also recover acceptable estimates of sea ice thickness when a thin, conductive, partially melted sea ice layer was present, and could determine shallow, sub-ice bathymetry in brackish water. As expected, 1D transformations and inversions of synthetic data for a three-dimensional pressure ridge keel structure contained artifacts, notably broadening of the apparent width of the keel.Prior to inverting a field data set acquired over rather thin (~ 0.5 m) Antarctic sea ice, we found it necessary to recalibrate the phase angle of the measurements using a phasor diagram-based method. Direct transformation of a single channel from the recalibrated data set produced more accurate estimates of sea-ice thickness than formal inversion of multi-channel data. We suggest that the least squares inversion methods are inferior in this situation because of the particular characteristics of the two-frequency HEM system used in this evaluation; the extreme differences in sensitivity of high and low frequency data components, the overall low sensitivity to sea ice conductivity (especially for thin ice), and the partially low signal-to noise ratios of the measurements. The data sets used in this study will be made available to the public to allow alternate inversion approaches to be applied and evaluated. It is suggested that inclusion of parameter bounds and other forms of regularization could help to improve the inversion results. 相似文献
12.
Zhisheng An Sumin Wang Xihao Wu Mingyang Chen Donghuai Sun Xiuming Liu Fubao Wang Li Li Youbin Sun Weijian Zhou Jie Zhou Xiaodong Liu Huayu Lu Yunxiang Zhang Guangrong Dong Xiaoke Qiang 《中国科学D辑(英文版)》1999,42(3):258-271
On the basis of a newly-constructed record of magnetic susceptibility (SUS) and the depositional rate change of eolian loess-red
clay sequences in the last 7.2 Ma BP from the hea Plateau, together with a cornperison of a record of °18O values from the equatorial East Pacific Ocean and eolian Quartz flux variations fmm the North Pacific Ocean, the evolutiomuy
process of the Late Cenozoic Great Glaciation in the Northern Hemisphere can be divided into three stages: the arrival stage
around 7.2–3.4 Ma BP, the initial stage at about 3.4—2.6 Ma BP, and the Great Ice Age since 2.6 Ma BP. The evolution of the
East Asian monsoon is characterized by paid winter and summer monsoons, and it is basically composed of the initial stage
of weak winter and summer monsoons, the transitional stage of simultaneous increase in intensity of winter and summer monsoons,
and the prevailing stage of strong winter and week summer monsoons, or weak winter and strong summer monsoons. The Late Cenowic
global tectonic uplift, paaicdarly the Qinghai-Xizang Plateau uplift and the associated CO2 concentration variation, controls the dng processes of the onset of Great Glaciation and the long-term changes of East Asian
monsoom climate in the Northern Hemisphere to a large extent. The accelerating uplift of the Qinghai-Xizang Plateau between
3.4 and 2.6 Ma BP provided an important driving force to global climiatic change.
Project supported by the foundation of Chinese Academy of Sciences (Grant No. KZ951-A1-402), the State Science and Technology
Committee (Grant No. 95-pre-40)and the Chinese Nature Science Foundation (Grant No. 49672140) 相似文献
13.
本文介绍了在B隧道勘查中应用高分辨电磁成像技术探测隐伏构造的一个成功实例。数据采集采用高频电磁成像系统(STRATAGEM EH4,频率范围从1Hz到90kHz)。野外采集正交的电磁场分量,从地磁成像剖面中提取目标体有关电磁学信息。为获取高质量的采集数据,野外采用包含天然场源和全张量可控源的混合场源。B隧道坐落在位于中国中部的湖北省的西部,隧道埋深不到200m,但区域地质作用导致它的地质机构十分复杂。第一次勘查过程中,勘探人员误把一个脱落体的露头当成基岩面,施工过程中出现了冒顶。第二次勘探时采用高分辨电磁法和折射地震法,这次勘探找到了隐伏的基岩面和一个隐伏断裂。勘探结果与后来隧道挖掘揭示的构造吻合。 相似文献
14.
Constraining the stepwise migration of the eastern Tibetan Plateau margin by apatite fission track thermochronology 总被引:8,自引:1,他引:8
LAI QingZhou ? DING Lin WANG HongWei YUE YaHui & CAI FuLong Institute of Geology Geophysics Chinese Academy of Sciences Beijing China Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing China 《中国科学D辑(英文版)》2007,50(2):172-183
Granites sampled from Garzê-Litang thrust, Longmen Shan thrust, Garzê and Litang strike-slip faults in the eastern Tibetan Plateau have been analyzed with apatite fission track thermochronological method in this study. The measured fission track apparent ages, combined with the simulated annealing mod- eling of the thermal history, have been used to reconstruct the thermal evolutionary histories of the samples and interpret the active history of the thrusts and faults in these areas. Thermal history mod- eling shows that earlier tectonic cooling occurred in the Garzê-Litang thrust in Miocene (~20―16 Ma) whereas the later cooling occurred mainly in the Longmen Shan thrust since ~5 Ma. Our study sug- gests that the margin of eastern Tibetan Plateau was extended by stages: through strike-slip faults deformations and related thrusts, the upper crust formed the Garzê-Litang margin in the Miocene epoch and then moved to the Longmen Shan margin since ~5 Ma. During this process, the deformations of different phases in the eastern Tibetan Plateau were absorbed by the thrusts within them and conse- quently the tectonic events of long-distance slip and extrusion up to hundreds of kilometers have not been found. 相似文献
15.
There are two kinds of methods in researching the crust deformation: geophysical method and geometrical (or observational)
method. Considerable differences usually exist between the two kinds of results, because of the datum differences, geophysical
model errors, observational model errors, and so on. Thus, it is reasonable to combine the two kinds of information to collect
the crust deformation information. To use the reliable geometrical and geophysical information, we have to control the observational
and geophysical model error influences on the estimated deformation parameters, and to balance their contributions to the
evaluated parameters. A hybrid estimation strategy is proposed here for evaluating the deformation parameters employing an
adaptively robust filtering. The effects of measurement outliers on the estimated parameters are controlled by robust equivalent
weights. Adaptive factors are introduced to balance the contribution of the geophysical model information and the geometrical
measurements to the model parameters. The datum for the local deformation analysis is mainly determined by the highly accurate
IGS station velocities. The hybrid estimation strategy is applied in an actual GPS monitoring network. It is shown that the
hybrid technique employs locally repeated geometrical displacements to reduce the displacement errors caused by the mis-modeling
of geophysical technique, and thus improves the precision of the estimated crust deformation parameters.
Supported by National Natural Science Foundation of China (Grant Nos. 40774001 and 40841021) and National High Technology
Research and Development Program of China (Grant No. 2007AA12Z331) 相似文献
16.
Hydrogen and oxygen isotope studies were carried out on mineral separates from high to ultrahigh pressure metamorphic rocks
at Huangzhen and Shuanghe in the eastern Dabie Mountains, East China. The δ18O values of eclogites cover a wide range of −5‰ to+9‰, but the δD values of micas fall within a narrow range of −85% to −70‰.
Both equilibrium and disequilibrium oxygen isotope fractionations were observed between quartz and the other minerals, with
reversed fractionations between omphacite and garnet in some eclogite samples. The δ18 O values of −5‰ to −1‰ for some of the eclogites represent the oxygen isotope compositions of their protoliths which underwent
meteoric water-rock interaction prior to plate subduction. The preservation of oxygen isotope heterogeneity in the eclogites
implies a channelized flow of fluids during progressive metamorphism caused by rapid subduction. Retrograde metamorphism has
caused oxygen and hydrogen isotope disequilibria between some of the minerals, but the fluid for retrograde reactions was
internally buffered in the stable isotope compositions.
Project supported by the Chinese Ministry of Science and Technology (Grant No. 95-Pre-39), the National Natural Science Foundation
of China (Grant Nos. 49794042, 49473173 and 49453003) and the Chinese Academy of Sciences (Grant No. KZ951-A1-401-5) 相似文献
17.
North Pacific sea ice cover, a predictor for the Western North Pacific typhoon frequency? 总被引:13,自引:0,他引:13
Fan Ke 《中国科学D辑(英文版)》2007,50(8):1251-1257
The relationship between the sea ice cover in the North Pacific and the typhoon frequency has been studied in this paper. It follows that the index for the sea ice cover in the North Pacific (ISA) both in December-January-February (DJF) and in March-April-May (MAM) is negatively correlated with annual typhoon number over the western North Pacific (TNWNP) during 1965―2004, with correlation coeffi-cients of -0.42 and -0.49 respectively (above 99% significant level). Large sea ice cover in the North Pacific tends to decrease TNWNP. Positive ISA (MAM) is associated with the tropical circulation and SST anomalies in the North Pacific, which may lead to unfavorable dynamic and thermal conditions for typhoon genesis over WNP from June to October (JJASO). The variability of the atmospheric circula-tion over the North Pacific, associated with the ISA anomaly in MAM is connected to the tropical at-mospheric circulation variability in MAM via the teleconnection wave train. Besides, as the tropical circulation has strong seasonal persistency from the MAM to JJASO, thus, the ISA in MAM-related variability of the tropical atmospheric circulation as well as the SST can affect the typhoon activity over the western North Pacific. 相似文献
18.
Geochemical characteristics and genesis of Dachadaban ophiolite in North Qilian area 总被引:6,自引:0,他引:6
There are three groups of pillow volcanics in the Dachadaban ophiolite. Group 1 is typical boninite, enriched in Si, Mg and
depleted in Ti, HREE and HFSE; group 2 is the evolved boninite, slightly higher abundance of Ti, HREE, HFSE and large variation
of Mg’ due to fractional crystallization; and group 3 is tholeiite with MORB character. The existence of MORB and boninite
indicates that the Dachadaban ophiolite was probably formed in islandare and back-arc environments.
Project supported by both the Department of Foundation Research and High Technology, State Science and Technology Commission
of PRC, and the National Natural Science Foundation of China (Grant No. 49472101). 相似文献
19.
Black carbon aerosols and their radiative properties in the Pearl River Delta region 总被引:13,自引:0,他引:13
Dui Wu JieTai Mao XueJiao Deng XueXi Tie YuanHang Zhang LiMin Zeng Fei Li HaoBo Tan XueYan Bi XiaoYing Huang Jing Chen Tao Deng 《中国科学D辑(英文版)》2009,52(8):1152-1163
The climatic and environmental effects of atmospheric aerosols are a hot topic in global science community, and radiative
properties of the aerosols are one of the important parameters in assessing climatic change. Here we studied the black carbon
concentration and absorption coefficient measured with aethalometers, scattering coefficient measured with nephelometers,
and single scattering albedo derived at an atmospheric composition watch station in Guangzhou from 2004 to 2007. Our main
results are as follows. The data of black carbon concentration and absorption coefficients measured with instruments cannot
be directly used until they are measured in parallel with internationally accepted instruments for comparison, calibration,
and reduction. After evaluation of the data, the result shows that the monthly mean of BC concentration varies 3.1–14.8 μg·m−3 and the concentration decreases by about 1 μg·m−3 in average over the four years; It is higher in the dry season with a multi-year mean of 8.9 μg/m3 and lower in the rainy season with a multi-year mean of 8.0 μg·m−3; The extreme maximum of monthly mean concentration occurred in December 2004 and extreme minimum in July 2007, and a 4-year
mean is 8.4 μg·m−3. It is also shown that monthly mean scattering coefficient derived varies 129 −565 Mm−1, monthly mean absorption coefficient 32–139 Mm−1, and monthly mean single scattering albedo 0.71–0.91, with annual mean values of 0.80, 0.82, 0.79 and 0.84 for 2004, 2005,
2006 and 2007, respectively. Three instruments were used to take simultaneous measurements of BC in PM10, PM2.5, and PM1 and the results showed that PM2.5 took up about 90% of PM10 and PM1 accounted for about 68% of PM2.5, and BC aerosols are mainly present in fine particulates. The variability of BC concentrations is quite consistent between
the Nancun station (141 m above sea level) and the Panyu station (13 m above sea level), which are 8 km apart from each other.
The concentration in higher altitude station (Panyu) is consistently lower than the lower altitude station (Nancun), and the
difference of annual mean is about 4 μg·m−3.
Supported by Natural Science Foundation of China (Grant Nos. U0733004, 40375002, 40418008, 40775011), National High Technology
R & D Program of China (Grant Nos. 2006AA06A306 and 2006AA06A308) and National Basic Research Program of China (Grant No.
2005CB422207) 相似文献
20.
Cyclostratigraphy of the Induan (Early Triassic) in West Pingdingshan Section, Chaohu, Anhui Province 总被引:1,自引:0,他引:1
The Induan sequence in the West Pingdingshan Section, Chaohu, Anhui Province, displays a series of superimposed mudstone/limestone cycles. The lithological character of the cycles, combined with power spectral and wavelet analysis of magnetic susceptibility readings, reveals 12 short eccentricity and 56 precession Milankovitch cycles - obliquity cycles are not apparent. The uniformity of cycle thicknesses indicates a stable depositional setting making this section ideal to perform various geo-logical studies. Accordingly, the Induan Stage is estimated to have lasted 1.1 Ma, and the depositional rate for this part of the section is about 3.7 cm/ka. This places the Induan-Olenekian boundary in the West Pingdingshan Section at about 251.5 Ma based on an age of 252.6 Ma for the Permian-Triassic boundary. 相似文献