A mass mortality of subtropical intertidal populations of the sea urchin Paracentrotus lividus: analysis of potential links with environmental conditions

An outbreak of bald sea urchin disease was detected affecting intertidal populations of the edible temperate species Paracentrotus lividus at its southernmost geographical limit. The mortality event was detected in three sites (Güímar, Palmar and Alcalá) off Tenerife, Canary Islands (Northeastern Atlantic), in October 2003, coinciding with the highest sea surface temperatures (SST) and the lowest wave heights of the year. The prevalence of infection reached 100% but did not affect equally all studied sites or the different size classes. The disease was more prevalent in large sea urchins (>40 mm). The prevalence appeared to be positively correlated with the environmental variable SST and negatively correlated with wave height. In October 2004, only two infected urchins were found (prevalence 1%) at one of the studied sites. However, during 2004 no such extreme values of temperature and wave height were observed. We conclude that high SSTs and low wave heights such as those observed during 2003 are conditions that may trigger outbreaks of urchin disease.     

Methods of setting depth range with credibility of conductor for deepwater drilling based on probability statistics

Becasuse of the deep water depth and long riser of deepwater drilling, the stability of subsea wellhead is threatened. Meanwhile, the setting depth of conductor directly affects the mechanical stability of subsea wellhead. Through analyzing the impact of different factors on the setting depth of conductor, we found that the bearing capacity growth factor of subsea soil has a great influence on the setting depth of conductor. However, the coefficient is a regional and empirical constant, which seriously affects the accuracy and reliability of the results. In this paper, probability statistics and geostatistics methods are employed to count the bearing capacity growth factor of target point's adjacent wells, as well as transplant and predict the target point through differential arithmetic, which can obtain the predictive value of target point's coefficient containing probability information. Finally, we can obtain the setting depth range with credibility of conductor. This is conducive to designers to calculate the setting depth of conductor with other uncertain factors taken into account, and reasonably control the potential risks.     

The vertical structure of the atmospheric boundary layer over the central Arctic Ocean

The tropopause height and the atmospheric boundarylayer （PBL） height as well as the variation of inversion layer above the floating ice surface are presented using GPS （global position system ） radiosonde sounding data and relevant data obtained by Chinas fourth arctic scientific expedition team over the central Arctic Ocean （86°-88°N, 144°-170°W） during the summer of 2010. The tropopause height is from 9.8 to 10.5 km, with a temperature range between -52.2 and -54.10C in the central Arctic Ocean. Two zones of maximum wind （over 12 m/s） are found in the wind profile, namely, low- and upper-level jets, located in the middle troposphere and the tropopause, respectively. The wind direction has a marked variation point in the two jets from the southeast to the southwest. The average PBL height determined by two methods is 341 and 453 m respectively. These two methods can both be used when the inversion layer is very low, but the results vary significantly when the inversion layer is very high. A significant logarithmic relationship exists between the PBL height and the inversion intensity, with a correlation coefficient of 0.66, indicating that the more intense the temperature inversion is, the lower the boundary layer will be. The observation results obviously differ from those of the third arctic expedition zone （800-85° N）. The PBL height and the inversion layer thickness are much lower than those at 870-88° N, but the inversion temperature is more intense, meaning a strong ice- atmosphere interaction in the sea near the North Pole. The PBL structure is related to the weather system and the sea ice concentration, which affects the observation station.     

The comparison of altimeter retrieval algorithms of the wind speed and the wave period

With the launch of altimeter,much effort has been made to develop algorithms on the wind speed and the wave period.By using a large data set of collocated altimeter and buoy measurements,the typical wind speed and wave period algorithms are validated.Based on theoretical argument and the concept of wave age,a semi-empirical algorithm for the wave period is also proposed,which has the wave-period dimension,and explicitly demonstrates the relationships between the wave period and the other variables.It is found that Ku and C band data should be applied simultaneously in order to improve either wind speed or wave period algorithms.The dual-band algorithms proposed by Chen et al.(2002) for the wind speed and Quilfen et al.(2004) for the wave period perform best in terms of a root mean square error in the practical applications.     

北太平洋500hpa候高度场的主成分分析

对太平洋500hPa候高度场和距平场进行了主成分分析,得出反映500hPa候高度特征的典型场。指出候高度场的第1特征向量的空间型是季节变化的主要型,它可解释总方差的74.5％,候高度场的其余特征向量与距平场的特征向量是按顺序的对应相似。这些典型场可以很好地描述北太平洋的大气环流特征。距平场的第1特征向量空间型清楚地反映了与厄尔·尼诺现象有关的环流型。     

神经网络BP算法在GPS高程转换中粗差探测的尝试

引入神经网络的BP算法中稳定、收敛速度快的Levenberg—Marquardt算法,进行GPS高程转换中的粗差探测,提出了LM粗差探测法。通过实验做出分析比较,得出了实用可行的计算方法。     

Sea surface height anomaly and geostrophic circulation variations in the South China Sea from TOPEX/POSEIDON altimetry

The sea surface height anomaly (SSHA) and geostrophic circulation in the South ChinaSea (SCS) are studied using TOPEX/POSE1DON (T/P) altimetry data. The SSHA, which is obtained after tidal correction based on the tidal results from T/P data, is predominated by seasonal alternating monsoons. The results reveal that the SSHA in the central part of the SCS is positive in spring and summer, but negative in autumn and winter. It is also found that the SSHA in the SCS can be approached with the sum of tidal constituents SA and SSA. The geostrophic circulations in the SCS are calculated according to sea surface dynamic topography, which is the sum of SSHA and mean sea surface height. It is suggested that the circulation in the upper layer of the SCS is generally cyclonic and notably western intensified during autumn and winter, while the western intensification is weak during spring and summer. It is also indicated that the Kuroshio intrudes into the northeastern SCS throuth the Luzon Strait in winter. But ther     

北太平洋海浪场和风场特征分析

利用欧洲中尺度天气预报中心(ECMWF——European Centre for Medium-Range Weather Forecasts)的1979年1月2014年12月逐6 h的ERA-Interim有效波高和10 m风场资料,分析了近36年期间北太平洋海域海浪场和风场的变化特征。结果表明:1)中低纬度的西北太平洋波高有逐年线性递增趋势,大约在0.2~0.6 cm/a,而低纬度的太平洋东北部海域则以-0.4~-0.2 cm/a的趋势减小。2)风速线性变化趋势显著的区域主要集中在太平洋东北部低纬度海域,约以1.0~2.0 cm/(s·a)的速度在增加。而日本岛四周、菲律宾半岛以南等海域大都以-1.0~-0.5 cm/(s·a)的速度减小。3)北太平洋海域波高和风速都具有明显的季节变化特征,两者具有很强的相关性。西风带内有一个个波高超过10 m的风暴圈,其波高受风浪和涌浪的双重作用。这可为航海、海洋工程设计、军事及海洋能开发与利用等方面提供科学依据。     

储层毛细管压力曲线在东海油气储量计算中的应用

本文阐述了利用储层毛细管压力曲线计算含油炮和度的方法,该方法在东海油气储量计算中取得良好的结果。     

一种高度测量方法的探讨

高度测量可以用水准测量、三角高程测量、数字化直接测量等多种测量方法,当前由于结构复杂的建构筑物日益增多,对于这类建构筑物的高度测量中,不一定都能顺利施测,常用的测量方法显示出其局限性。本文以对中国女排三连冠纪念碑碑高测量为例,介绍了一种新的高度测量方法——两站测角高度测量法。