南海北部陆坡晚第四纪有机壁浮游藻类记录及其古环境 …   总被引：5，自引：1，他引：4  

吴国Xuan  孙湘君 《海洋地质与第四纪地质》2000,20(2):57-63

通过９２个样品分析,发现南海北部陆坡末次冰期以来２物中有机壁浮游藻类输入通量在新仙女木期和早全新世明显高于其它时期新仙女山的输入通量峰值及不同于Ｓｐｉｎｉｆｅｒｉｔｅｓｓｐｐ．组合（较暖期）和Ｐｒｏ－ｔｏｐｅｒｉｄｉｎｉｏｉｄ类孢囊组合（较冷期）的Ｏｐｅｒｃｕｌｏｄｉｎｍｉｕｍ ｃｅｔｒｏｃａｒｐｕｍ组合,表明当时表层少环境较为特殊,可能是水温偏低且较富营养的条件,早全新世的有机壁浮游藻类高输入通  相似文献   

Otolith microchemical evidence revealing multiple spawning site origination of the anadromous tapertail anchovy (Coilia nasus) in the Changjiang (Yangtze) River Estuary     

Zhongya Xuan  Tao Jiang  Hongbo Liu  Xiubao Chen  Jian Yang 《海洋学报(英文版)》2023,42(1):120-130

The estuarine tapertail anchovy(Coilia nasus) is a high-value commercial fish. Estimating the spawning site or hatchery origin and habitat is essential for its conservation. This study aimed to determine the habitat use and life history characteristics of C. nasus from the Changjiang River Estuary. We investigated the environmental signatures of strontium(Sr) and calcium(Ca) in the otoliths of the collected specimens using electron probe microanalysis; additionally, we examined their gonadal mat...  相似文献   

Numerical investigation of the effect of seasonal variations of depthof-closure on shoreline evolution     

Xuan Tinh Nguyen  Minh Thanh Tran  Hitoshi Tanaka  Trung Viet Nguyen  Yuta Mitobe  Cong Dien Duong 《国际泥沙研究》2021,36(1):1-16

The current study presents the effects of seasonal variations in the depth-of-closure(Dc)on shoreline evolution using a numerical,one-line shoreline model.Beach erosion of the southern beach of the Nha Trang Coast,which is located in south central of Vietnam,is selected as the study area.This study area is immensely influenced by the tropical monsoon climate that has a clear pattern of large waves in the northeast monsoon season and calm waves in the non-monsoon season.The analysis of the long-term measured shoreline variations from a video-camera system has found a strong correlation of these variations to the monsoon-dominated wave characteristics in the Nha Trang Bay.Therefore,a new approach for determining the depth-of-closure with consideration of the seasonal wave climate changes is purposed in the current study.By implementing this new approach into a numerical,one-line shoreline model,it is found that the seasonal variations of Dc appear to better describe the periodical shoreline evolution due to the monsoon-dominated wave characteristics for the Nha Trang Coast.Such important findings are considered to commonly apply for monsoon-dominated coastal regions in general.These findings are useful information not only for scientific readers but also for the coastal authorities and managers in order to make better countermeasure plans against this kind of erosion mechanism in the future.  相似文献   

Accumulation conditions and enrichment mechanism of Shale gas in Nangao section, Yangtze Platform,S.China     

LUO Chao  LIU Shugen  SUN Wei  RAN Bo  YANG Di  ZHANG Xuan  WANG Shiyu  YE Yuehao 《《地质学报》英文版》2013,87(Z1):574-575

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Estimation of tropical cyclone parameters and wind fields from SAR images     

ZHOU Xuan  YANG XiaoFeng  LI ZiWei  YU Yang  BI HaiBo  MA Sheng  LI XiaoFeng 《中国科学:地球科学(英文版)》2013,56(11):1977-1987

The traditional method of Synthetic Aperture Radar(SAR)wind field retrieval is based on an empirical relation between the near surface winds and the normalized radar backscatter cross section to estimate wind speeds,where this relation is called the geophysical model function(GMF).However,the accuracy rapidly decreases due to the impact of rainfall on the measurement of SAR and the saturation of backscattered intensity under the condition of tropical cyclone.Because of no available instrument synchronously monitoring rain rate on the satellite platform of SAR,we have to derive the precipitation of the SAR observation time from non-simultaneous passive microwave observations of rain in combination with geostationary IR images,and then use the model of rain correction to remove the impact of rain on SAR wind field measurements.For the saturation of radar backscatter cross section in high wind speed conditions,we develop an approach to estimate tropical cyclone parameters and wind fields based on the improved Holland model and the SAR image features of tropical cyclone.To retrieve the low-to-moderate wind speed,the wind direction of tropical cyclone is estimated from the SAR image using wavelet analysis.And then the maximum wind speed and the central pressure of tropical cyclone are calculated by a least square minimization of the difference between the improved Holland model and the low-to-moderate wind speed retrieved from SAR.In addition,wind fields are estimated from the improved Holland model using the above-mentioned parameters of tropical cyclone as input.To evaluate the accuracy of our approach,the SAR images of typhoon Aere,typhoon Khanun,and hurricane Ophelia are used to estimate tropical cyclone parameters and wind fields,which are compared with the best track data and reanalyzed wind fields of the Joint Typhoon Warning Center(JTWC)and the Hurricane Research Division(HRD).The results indicate that the tropical cyclone center,maximum wind speed,and central pressure are generally consistent with the best track data,and wind fields agree well with reanalyzed data from HRD.  相似文献   

Characteristics and environmental significance of Ca, Mg, and Sr in the soil infiltrating water overlying the Furong Cave, Chongqing, China   总被引：2，自引：0，他引：2  

LI JunYun  LI TingYong  WANG JianLi  XIANG XiaoJing  CHEN YunXuan  LI Xuan 《中国科学:地球科学(英文版)》2013,56(12):2126-2134

This paper explores the influence of the local meteoric conditions,the overlying soil on the concentrations of Ca,Mg,and Sr,and the ratios of Mg/Ca,Sr/Ca,and Mg/Sr in soil infiltrating water(SIW).An in situ monitoring program was carried out above the Furong Cave throughout 2010 to collect data on SIW,monthly temperature and rainfall,and the geochemical composition and granularity of soils.The discharge of SIW responded quickly to the local rainfall,and its residence time was the primary factor affecting the Ca,Mg,and Sr content of the SIW.The high concentrations of Ca,Mg,and Sr in the SIW during April should be attributed primarily to the prolonged residence of SIW in the soil during the local dry seasons of winter and early spring.The maximum Mg/Sr ratio also occurred in April.The ratio of Mg/Ca in SIW is positively correlated with prolonged residence time and with high temperatures,which do not strongly affect the ratio of Sr/Ca.The Mg/Ca ratio was lowest when the Sr/Ca ratio was highest because plant metabolism increased the absorption of Ca and Mg,but not Sr,and also because higher temperatures enhanced the dissolution of Mg more than that of Sr.These different responses of Mg and Sr to temperature increases resulted in high Mg/Sr ratios during July and August.  相似文献   

Dynamic Controls on the Formation of Mantle Plume Beneath the South China Sea Region     

YU Xuan  HOU Guiting 《《地质学报》英文版》2016,90(Z1):168-168

正The South China Sea(SCS)has attracted intensive structural and geophysical research over the past decades,with a focus on its extensional history and relevant dynamic tectonic models.Seismic tomographic images obtained  相似文献   

A Two-Moment Bulk Microphysics Coupled with a Mesoscale Model WRF: Model Description and First Results   总被引：1，自引：0，他引：1  

GAO Wenhu  ZHAO Fengsheng  HU Zhijin  FENG Xuan 《大气科学进展》2011,28(5):1184-1200

The Chinese Academy of Meteorological Sciences (CAMS) two-moment bulk microphysics scheme was adopted in this study to investigate the representation of cloud and precipitation processes under different environmental conditions.The scheme predicts the mixing ratio of water vapor as well as the mixing ratios and number concentrations of cloud droplets,rain,ice,snow,and graupel.A new parameterization approach to simulate heterogeneous droplet activation was developed in this scheme.Furthermore,the improved CAMS scheme was coupled with the Weather Research and Forecasting model (WRF v3.1),which made it possible to simulate the microphysics of clouds and precipitation as well as the cloud-aerosol interactions in selected atmospheric condition.The rain event occurring on 27-28 December 2008 in eastern China was simulated using the CAMS scheme and three sophisticated microphysics schemes in the WRF model.Results showed that the simulated 36-h accumulated precipitations were generally agreed with observation data,and the CAMS scheme performed well in the southern area of the nested domain.The radar reflectivity,the averaged precipitation intensity,and the hydrometeor mixing ratios simulated by the CAMS scheme were generally consistent with those from other microphysics schemes.The hydrometeor number concentrations simulated by the CAMS scheme were also close to the experiential values in stratus clouds.The model results suggest that the CAMS scheme performs reasonably well in describing the microphysics of clouds and precipitation in the mesoscale WRF model.  相似文献   

An improved wind speed algorithm for “Jason-1” altimeter under tropical cyclone conditions     

QIN Bangyong  ZHOU Xuan  ZHANG Honglei  YANG Xiaofeng  LU Rong  YU Yang  SHI Lijian 《海洋学报(英文版)》2014,33(7):83-88

Rain effect and lack of in situ validation data are two main causes of tropical cyclone wind retrieval errors. The National Oceanic and Atmospheric Administration＇s Climate Prediction Center Morphing technique （CMORPH） rain rate is introduced to a match-up dataset and then put into a rain correction model to remove rain effects on ＂Jason-1＂ normalized radar cross section （NRCS）; Hurricane Research Division （HRD） wind sPeed, which integrates all available surface weather observations, is used to substitute in situ data for establishing this relationship with ＂Jason-l＂ NRCS. Then, an improved ＂Jason-l＂ wind retrieval algorithm under tropical cyclone conditions is proposed. Seven tropical cyclones from 2003 to 2010 are studied to validate the new algorithm. The experimental results indicate that the standard deviation of this algorithm at C-band and Ku-band is 1.99 and 2.75 m/s respectively, which is better than the existing algorithms. In addition, the C-band algorithm is more suitable for sea surface wind retrieval than Ku-band under tropical cyclone conditions.  相似文献   

Research progress in cold region wetlands, China     

YaYi Tan  Xuan Wang  ZhiFeng Yang  YuLi Wang 《寒旱区科学》2011,3(5):0441-0447

China has some of the most abundant wetland resources in the world. Cold region wetlands cover more than 60% of the total natural wetlands in China and play an indispensable role in global climate regulation, water holding, uptake and emission of greenhouse gases, and biodiversity conservation. Because cold region wetlands are sensitive to climatic and environmental changes, it is important for ecological conservation and environmental management to summarize and analyze current research progress on these specific ecosystems. This paper reviews the focus of present studies on the typical cold region wetlands in the northeast region and the Qinghai-Tibet Plateau of China from several aspects as follows: types and distribution, responses of permafrost to climatic changes, uptake and emission of greenhouse gas, eco-hydrological processes, and vegetation succession. Our conclusions are: global warming has a long-term and serious impact on cold region permafrost; emission of greenhouse gases has great temporal and spatial heterogeneity; and hygrophytes in the cold region wetlands have been generally replaced by xerophytes, although it is still unclear whether the vegetation diversity index has increased or decreased. Based on this review, some key topics for future study are recommended as follows: (1) the response of degeneration of cold region permafrost at various spatial and temporal scales; (2) prediction of wetland degeneration tendency by coupling weather, soil, and hydrological models; (3) evaluation of carbon storage; (4) the actual response mechanisms of greenhouse gases to climatic changes; and (5) development of water requirement calculation methods tailored to the unique ecosystems of cold region wetlands.  相似文献