Paleoclimate Changes during the Early Oligocene in the Hoh Xil Region, Northern Tibetan Plateau   总被引：2，自引：0，他引：2  

Alain TRENTESAUX 《《地质学报》英文版》2003,77(4)

Sedimentological, cyclic-stratigraphic, paleomagnetic, and clay-mineralogical studies on the early Oligocene Yaxicuo Group in the Hoh Xil Basin, the largest Cenozoic sedimentary basin in the hinterland of the Tibetan Plateau, provide abundant information of paleoclimate changes. A 350-m thick section in the middle-lower Yaxicuo Group was analyzed to reveal the climatic history that occurred in the Hoh Xil region during the early Oligocene interval 31.30-30.35 Ma, dated with the paleomagnetic chronostratigraphy. The results indicate that arid and cold climate dominated the Hoh Xil region during the early Oligocene in general, being related to the global cooling and drying events that occurred in the earliest Oligocene. Within this period, relatively warm and wet climate accompanied by strong tectonic activity occurred in the 31.05-30.75 Ma interval; while arid and cold climate and relatively inactive tectonics occurred in the 31.30-31.05 and 30.75-30.35 Ma intervals. Furthermore, spectral analyses of hig  相似文献   

Correlation between successive wave heights and periods in mixed sea states     

Germn R. Rodríguez  C. Guedes Soares 《Ocean Engineering》2001,28(8)

The degree of dependence between successive wave heights and periods is examined for sea states resulting from the combination of a remotely generated wave field and a locally generated wave system, based on simulated wave records. The sea states analysed represent situations that are swell dominated, wind–sea dominated or they have equivalent energy in the wind–sea and swell components. Results of the analysis of the simulated data have been compared with those expected from the theories for the joint distributions of consecutive wave heights and periods and with the results from a Pierson–Moskowitz target spectrum.  相似文献   

渤海天文-风暴潮数值模拟和一种多年一遇极值水位的计算方法   总被引：6，自引：1，他引：6       下载免费PDF全文

于宜法  俞聿修 《海洋学报》2003,25(4):10-17

在渤海选用了82个强天气过程,利用三维模式模拟了海区的天文-风暴潮,模式经实测资料检验,获得了较满意的模拟结果。根据渤海沿岸主要验潮站观测年极值高(低)水位和年极值风增(减)水所得到的多年一遇高(低)水位和多年一遇风增(减)水,以及天文最高(最低)潮位,建立了由多年一遇风增(减)水和天文最高(最低)潮位的线性组合计算多年一遇高(低)水位的计算公式,并以此公式推算了渤海海区5个典型地区的多年一遇高(低)水位,供海洋工程设计时使用。  相似文献   

The effect of wave period filtering on wave power extraction and device tuning     

Vengatesan Venugopal  George H. Smith 《Ocean Engineering》2007,34(8-9):1120-1137

The variations in the quantity of wave power available to a wave energy converter by filtering out short-period waves have been examined in this paper. Ocean wave data recorded at three different locations and water depths around northern Europe are used for this purpose along with numerically synthesized wave time series. A wave power ratio, defined as the ratio between the wave power for the filtered and unfiltered data, is calculated for each data set, and the variation of this quantity with the degree of filtering is investigated. Two new parameters namely, R and S are defined to quantify the effect of this filtering on the variation of wave-to-wave period and height. It is shown that removing the shorter period waves has little effect upon the power available for extraction but may significantly reduce the rate at which the wave energy converter must retune to achieve optimum power conversion.  相似文献   

Projected Changes in Temperature and Precipitation Extremes over China as Measured by 50-yr Return Values and Periods Based on a CMIP5 Ensemble     

Ying XU  Xuejie GAO  Filippo GIORGI  Botao ZHOU  Ying SHI  Jie WU  Yongxiang ZHANG 《大气科学进展》2018,35(4):376-388

Future changes in the 50-yr return level for temperature and precipitation extremes over mainland China are investigated based on a CMIP5 multi-model ensemble for RCP2.6, RCP4.5 and RCP8.5 scenarios. The following indices are analyzed:TXx and TNn(the annual maximum and minimum of daily maximum and minimum surface temperature), RX5 day(the annual maximum consecutive 5-day precipitation) and CDD(maximum annual number of consecutive dry days). After first validating the model performance, future changes in the 50-yr return values and return periods for these indices are investigated along with the inter-model spread. Multi-model median changes show an increase in the 50-yr return values of TXx and a decrease for TNn, more specifically, by the end of the 21 st century under RCP8.5, the present day 50-yr return period of warm events is reduced to 1.2 yr, while extreme cold events over the country are projected to essentially disappear.A general increase in RX5 day 50-yr return values is found in the future. By the end of the 21 st century under RCP8.5, events of the present RX5 day 50-yr return period are projected to reduce to 10 yr over most of China. Changes in CDD-50 show a dipole pattern over China, with a decrease in the values and longer return periods in the north, and vice versa in the south. Our study also highlights the need for further improvements in the representation of extreme events in climate models to assess the future risks and engineering design related to large-scale infrastructure in China.  相似文献   

1965-2014年北京西郊地区植物观赏期对气候变化的响应   总被引：1，自引：0，他引：1  

高新月  戴君虎  张明庆 《地理研究》2018,37(12):2420-2432

基于1965-2014年北京地区50种植物物候数据和同期日均温等气象资料,运用相关、回归分析法分析了北京地区绿叶观赏期、观花期和秋叶观赏期（开始日、结束日、时间长度）的变化趋势、变化形式及其对气候变化的响应情况。结果表明：① 北京西郊地区50种植物的绿叶观赏期为4月14日-10月15日,观赏期长度为163~219天。观花期为4月29日-5月17日,观花期长度为6~77天。秋叶观赏期为10月15日-11月14日,观赏期长度为16~41天。② 近50年来,北京西郊地区50种植物的3个观赏期都发生了一定程度的变化。绿叶观赏期开始日提前3.1天/10a,结束日推迟3.6天/10a,观赏期延长6.8天/10a。观花期开始日提前1.6天/10a,结束日提前0.5天/10a,观赏期延长1.2天/10a。秋叶观赏期开始日推迟3.6天/10a,结束日推迟1.1天/10a,观赏期缩短2.5天/10a。③ 绿叶观赏期延长主要表现为开始日提前,结束日推迟。观花期延长主要表现为开始日提前程度大于结束日提前程度,春花植物和夏花植物的观花期延长和缩短的表现形式基本一致。秋叶观赏期缩短主要表现为开始日推迟程度大于结束日推迟程度。④ 春季气温升高1 ℃,绿叶观赏期开始日提前3.9天、结束日推迟5.2天;观花期开始日提前3.4天,结束日提前1.9天。秋季气温升高1 ℃,秋叶观赏期开始日和结束日分别推迟5.2天和2.2天。⑤ 将不同观赏期重叠搭配可营造不同色彩和风格的植被景观,进而设计出不同特色的景观观赏主题。植物观赏期的变化可为园林景观创新设计提供有力参考,为植物观赏活动时间的安排提供科学依据。  相似文献   

水稻不育系育性变化的气候学特征及其适应性分析     

姚克敏  杨亚新等 《南京气象学院学报》1995,18(1):72-78

根据光（温）敏雄性核不育系水稻的育性模型导出的育性转换临界温度和临界日长指标，用15个代表站1951－1988年逐日平均气温和理论日长分析了7001sN5088s和安农s-1三不育系的育性转换日期及不育期和发育期长度的气候学特征，为二系法杂交水稻的育性转换提供一种实用分析方法，并为生产提供依据。  相似文献   

Synoptic meteorological observations and weather conditions during MONTBLEX-90     

S K Srivastav 《Journal of Earth System Science》1995,104(2):189-220

In the present paper a review of meteorological observations conducted by India Meteorological Department during MONTBLEX-90, including intensive observation periods, has been made. Also, an exhaustive weather summary, discussing the special weather features that occurred during the MONTBLEX observational period, is presented. The paper has been prepared to provide a ready reference of the synoptic features to research workers who are utilizing MONTBLEX data for their studies.  相似文献   

北京西山的冰缘期和更新世自然环境   总被引：8，自引：1，他引：8  

郭旭东  严富华 《冰川冻土》1991,13(2):159-167

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新疆东准噶尔地区构造演化及主要成矿期     

冯益民 《西北地质科学》1991,(2)

笔者认为东准噶尔地区曾是古新疆克拉通的一部分,只是到了泥盆纪才演化成大洋。值得特别提出的是,大洋消失之后,经历了残留海盆阶段才开始碰撞造山。碰撞期后的岩浆作用和板内裂陷作用在该区特别发育,而且形成相关的内生金属矿产。以大型内陆盆地沉降和山脉隆升为特征的陆内造山作用标志着大陆克拉通化的最终完成。成矿期与构造演化密切相关,自老而新划分了6个成矿期。  相似文献