Statistical analyses of sea state conditions in South China Sea     

Adekunle Osinowo  Xiaopei Lin  Dongliang Zhao  Zhifeng Wang 《中国海洋大学学报(英文版)》2017,16(3):357-369

The statistical characterization of sea conditions in the South China Sea(SCS) was investigated by analyzing a 30-year(1976–2005) numerically simulated daily wave height and wind speed data. The monthly variation of these parameters shows that wave height and wind speed have minimum values of 0.54 m and 4.15 ms~(-1), respectively in May and peak values of 2.04 m and 8.12 ms~(-1), respectively in December. Statistical analysis of the daily wave height and wind speed and the subsequent characterization of the annual, seasonal and monthly mean sea state based on these parameters were also done. Results showed that, in general, the slight sea state prevails in the SCS and has nearly the highest occurrence in all seasons and months. The moderate sea condition prevails in the winter months of December and January while the smooth(wavelets) sea state prevails in May. Furthermore, spatial variation of sea states showed that calm and smooth sea conditions have high occurrences(25%–80%) in the southern SCS. The slight sea condition shows the largest occurrence(25%–55%) over most parts of the SCS. High occurrences(8%–17%) of the rough and very rough seas distribute over some regions in the central SCS. Sea states from high to phenomenal conditions show rare occurrence(12%) in the northern SCS. The calm(glassy) sea condition shows no occurrence in the SCS.  相似文献   

河西走廊入口区下垫面对沙尘天气影响的模拟研究   总被引：1，自引：1，他引：0  

李丹华  隆霄  温晓培  江颖  孟晓文 《中国沙漠》2017,37(6):1210-1218

在利用常规观测资料统计分析2000—2011年和沙尘天气多发年河西走廊入口区代表站点春季风速分布特征的基础上,采用区域气候模式（Regcm4.3.5.6）和欧洲中心更新的4DVar同化的ERA-interim资料,分析了河西走廊入口区下垫面类型改变对2007年4月13日一次沙尘天气过程的影响。结果表明：沙尘暴爆发时,河西走廊为风速大值区,风速8～10 m·s^-1;区域气候模式模拟的沙尘特征量与站点观测的沙尘天气分布对比发现,模拟的沙尘区的发展变化能较好地表征这次沙尘天气过程的变化;河西走廊入口区植被由沙漠改为落叶阔叶林后,发生沙尘天气时该地区风速有所减小,减小平均值为3 m·s^-1,且风速越大,减小越明显。不同粒径沙尘的起沙率和沙尘粒子柱含量对下垫面类型改变的响应有所不同,减小量最大分别达到-50 mg·m^-2·d^-1和-50 mg·m^-2,0.01～5.0 μm粒径沙尘减小范围和强度相差不大,5.0～20 μm粒径沙尘由于粒径最大减小最明显,由于模式中考虑的2.5～5.0 μm粒径沙尘在大气中所占比例小,减小量级和范围最弱。改变下垫面类型使得起沙率和沙尘粒子柱含量在沙尘天气最强时刻减少最显著。  相似文献   

中国干线公路网络联结的城市通达性   总被引：74，自引：9，他引：65  

曹小曙  薛德升  阎小培 《地理学报》2005,60(6):903-910

以"最短路径模型"为基础,选取距离与时间两个特征指标以及联结两者的速度指标,分析了目前中国国家干线公路网络联结的城市通达性空间格局。结果显示,国家干线公路网络联结的城市呈现明显的"核心-外围"模式,通达性最高的50个城市集中分布在东部的中部地区,通达性最低的50个城市散布在西北、西南、东北等外围地区;通达性空间格局呈现同心圈层结构,由最优区域向外逐渐降低;国家干线公路网络联结的城市通达性空间格局具有显著的边界效应,在不同的速度状态下呈现波状形态变化;国家干线公路网络中行车速度从60~80 km/h的城市通达性变化显著大于80~100 km/h的城市通达性变化;120 km/h时速下,8小时以内每个城市连接的城市数量平均为33个,联结数量最多的城市集中分布在东部,平均每个城市可联结数量为70个,联结数量最少的城市分布在西北、西南、东北、东南,平均每个城市可联结数量为6个。未来国家干线公路网络除继续建设外,行车速度的提高将大大影响城市通达性的变化。  相似文献   

清代广州城市社会空间结构研究   总被引：5，自引：0，他引：5  

魏立华  闫小培  刘玉亭 《地理学报》2008,63(6):613-624

清代之前广州长期作为重要的外贸港口, 港市、对外贸易、多元文化及“蕃坊”等对 城市社会空间结构的影响很大; 清初广州确立“一口通商”, 对外贸易更趋繁荣, 西关及滨江 地带成为巨贾侨商集聚之地, 而城内的满族与汉族在社会地位、居住等方面呈现较大的分异。 从城市总体层面来看, 清代广州呈现“西商-东官” 的社会空间格局, 西关平原及“南关” 滨江地带“因港而商, 因商而富”, 城墙之内的老城区则一直作为官衙区及官僚贵族居住区, “因衙而尊, 因官而贵”, 这成为广州社会空间结构演进的历史主线。就清末的广州西关而言, 已分化为纺织机房区、新兴高级住宅区及洋商区等社会区类型, 具备殖民性河港贸易城市的 社会空间特征。自然条件对城市空间扩展的限制, “一口通商”的港市繁荣, 以及遵循封建 礼制的城建思想等成为影响清代广州社会空间结构的主要机制。  相似文献   

Application of shallow high-resolution transient electromagnetic method( TEM) in geological investigation of debris flow     

LIU Chenyang  ZHANG Xiaopei  DU Lizhi  WANG Yong 《世界地质(英文版)》2019,22(2):91-97

In the investigation of debris flow, the detection of the source area of the post-disaster debris flow is an important basis for evaluating the distribution of the debris flow accumulation layer and the subsequent control. In this paper, a shallow high-resolution TEM is used to detect the debris flow source area in Dashigou village, Yongji County, Jilin Province. The purpose of this investigation is to determine the depth range of debris flow damage. The detection results show that there is an obvious low resistance zone at about 10 m depth along the survey line, which is in good agreement with the drilling data and the high density electrical detection. It is proved that the depth is the maximum impact depth of the debris flow. The practical engineering proves that the method has high resolution in shallow layer detection, high efficiency and convenience in field acquisition. The maximum detection depth range of this method is 30--40 m, which meets the requirements of high efficiency and accurate detection for regional debris flow source area, and has high practical application value.  相似文献   

Quantifying the non-conservative production of potential temperature over the past 22000 years     

ZHANG Cunjie  HAN Xueshuang  LIN Xiaopei 《中国海洋湖沼学报》2019,(2)

The energy budgets of the ocean play a crucial role in the analysis of climate change. Potential temperature is traditionally used as a conservative quantity to express variations associated with "heat"in oceanography, such as the heat content and heat transport. However, potential temperature is usually not conserved during turbulent mixing, so the use of conservative temperature is more accurate. Based on climatological simulations under the modern and Last Glacial Maximum(LGM; ～21 ka; ka=thousand years ago), as well as a transient climate simulation of the past 22 000 years, we quantify the errors induced by the neglect of the non-conservation of potential temperature in paleo-climate research for the first time. The temperature error reaches 0.9°C near the coasts af fected by river discharges but is much smaller in the open oceans, typically 0.03°C above the main thermocline and less than 0.01°C elsewhere. The error of the ocean heat content(OHC) is roughly 3×10 22 J and is relatively steady over the past 22 000 years. However, the OHC increases to six times the original value during the last glacial termination from 20 ka to 7 ka. As a result, the relative OHC error decreases from 1.2% in the LGM climate to 0.14% in the modern climate. The error of the ocean meridional heat transport(OMHT) is generally smaller than 0.005 PW(1 PW=10 15 W),with very small temporal variations(typically 0.000 4 PW), and induces a relative OMHT error of typically0.3% over the past 22 000 years. Therefore, the neglect of the non-conservation of potential temperature induces a relative error of generally less than 1% in the analyses of basin-scale climate variations.  相似文献   

Co-variation of the surface wind speed and the sea surface temperature over mesoscale eddies in the Gulf Stream region:momentum vertical mixing aspect     

HE Jingjing  LIN Xiaopei 《海洋湖沼学报（英文）》2019,(4):1154-1164

The co-variation of surface wind speed and sea surface temperature (SST) over the Gulf Stream frontal region is investigated using high-resolution satellite measurements and atmospheric reanalysis data. Results show that the pattern of positive SST-surface wind speed correlations is anchored by strong SST gradient and marine atmospheric boundary layer (MABL) height front, with active warm and cold-ocean eddies around. The MABL has an obvious transitional structure along the strong SST front, with greater (lesser) heights over the north (south) side. The significant positive SST-surface wind-speed perturbation correlations are mostly found over both strong warm and cold eddies. The surface wind speed increases (decreases) about 0.32 (0.41) m/s and the MABL elevates (drops) approximate 55 (54) m per 1℃ of SST perturbation induced by warm (cold) eddies. The response of the surface wind speed to SST perturbations over the mesoscale eddies is mainly attributed to the momentum vertical mixing in the MABL, which is confirmed by the linear relationships between the downwind (crosswind) SST gradient and wind divergence (curl).  相似文献   

Application of ultrasonic CT method in nondestructive detection of interior defects in large scale concrete structural member of bridge     

Xiaopei ZHANG  Jianhui QIU  Jianjun NIU  Lizhi DU  Xuege WANG .College of Construction Engineering  Jilin university  Changchun  China.China Northeast Municipal Engineering Design  Research Institute  Changchun  China 《东北亚地学研究》2008,11(4):218-221

The ultrasonic computed tomography （USCT） method is derived from the basic principles of X-ray section scanning. This method records the arriving times of ultrasonic wave between the probes and the sources to ealculate the elastic wave velocity values in the section using the arrival times. Through analyzed the distribution Of elastic wave velocity in aim area, the information of the strength and the homogeneity of the investigated zone could be got indirectly. The authors introduced the operational principle of USCT and a practical case of using this method to detect the interior defects in large scale concrete structural member. Compared with other exploration methods, this method is more efficient and accurate.  相似文献   

Application of TSD tunnel seismic prediction system in karst area     

Lizhi DU  Xiaopei ZHANG  Jianjun NIU  Xuege WANG .College of Construction Engineering  Jilin University  Changchun  China.China Northeast Municipal Engineering Design  Research Institute  Changchun  China 《东北亚地学研究》2008,11(4):246-250

TSD is one of the classical methods of tunnel seismic prediction based on higher accuracy multi-wave multi-component seismology. The working principle of the TSD and an application example of the TSD on tunnel prediction in Chongqing are introduced in this paper. This system has two ports for speed signal and acceleration signal, and the equipment is more portable and easy to use. According to the application results we can conclude that the TSD prediction system is accurate and it has the wide application prospect in tunnel seismic detection.  相似文献   

Application of ultrasonic CT method in nondestructive detection of interior defects in large scale concrete structural member of bridge     

Xiaopei ZHANG  Jianhui QIU  Jianjun NIU  Lizhi DU  Xuege WANG 《世界地质(英文版)》2008,11(4)

The ultrasonic computed tomography (USCT) method is derived from the basic principles of X-ray section scanning. This method records the arriving times of ultrasonic wave between the probes and the sources to calculate the elastic wave velocity values in the section using the arrival times. Through analyzed the distribution of elastic wave velocity in aim area, the information of the strength and the homogeneity of the investigated zone could be got indirectly. The authors introduced the operational principle of USCT and a practical case of using this method to detect the interior defects in large scale concrete structural member. Compared with other exploration methods, this method is more efficient and accurate.  相似文献