中国近海棱梭群体形态学和耳石形态学研究          下载免费PDF全文

阳敏  刘璐  吴桢  吴天昊  谭颖琪  龙丹丹  高天翔  宋娜 《应用海洋学学报》2019,38(3):329-337

为研究棱梭不同地理群体间的形态差异,使用多元统计分析方法对采集自金门、厦门、虎门、湛江、北海和防城港6个地点邻近海域的棱梭群体样本的形态和矢耳石形态两方面进行比较研究。对棱梭样本的形态研究结合传统形态学和地标形态学开展,对矢耳石的形态研究则将传统耳石形态分析法和椭圆傅里叶分析法相结合,形态和耳石形态数据的分析结果相似。主成分分析结果表明从28个棱梭形态量度指标提取的前8个主成分累积贡献率为65. 868%,从85个耳石形态指标提取的前23个主成分的累积贡献率为79. 290%,根据临界值85. 000%可以推断这6个棱梭群体间形态和耳石形态上的差异不能够单独依靠少数指标来判断;聚类分析的结果总体显示出群体间差异与地理距离等因素相关联的分布规律;在判别分析中形态学量度指标的综合判别正确率为75. 9%,而耳石形态学指标的综合判别正确率略低,为69. 3%;对棱梭形态量度指标的单因子方差分析显示湛江棱梭群体与其他群体在形态上存在显著差异的量度指标较少。栖息地环境、饵料组成和海流等可能是导致形态学差异和耳石形态差异形成的主要因素。另一方面,理化因子的相似性和群体间的交流会减弱群体间形态和耳石形态的差异。  相似文献   

Statistical characterization of impact of system variables on temporal dynamics of groundwater in highly weathered regoliths     

V. Rasiah  J. D. Armour  A. L. Cogle 《水文研究》2007,21(18):2435-2446

In situations where the water table fluctuates during the rainy season the characterization of the impact of system variables on the temporal dynamics of the groundwater (GW) is essential to improve the understanding at catchment or regional scale behaviour of GW. In this study the appropriateness of the statistical parameters; mean, median, the 80^th percentile (PC80), coefficient of variation (CV), correlation coefficient (r), and multiple regression models were assessed to characterize the impact of system variables on the temporal dynamics of hydraulic head relative to ground surface (HH) during rainy seasons. The study was conducted from 1999 to 2003 in the wet tropical Johnstone River catchment (JRC) in north‐east Queensland, Australia. Piezometer wells were installed at 32 sites under cropping to 5–90 m depth on different soil types, landscape positions, and varying proximity to surface water bodies (i.e. four system variables). The HH was measured, at least at 10–15 day intervals during 1–5 consecutive rainy seasons. The HH in the 32 wells fluctuated throughout each of the five rainy seasons. The mean HH averaged over the seasons ranged from 1·1 to 17·2 m across the wells, the median from 0·9 to 17·3 m, and the PC80 from 0·3 to 16·1 m. The temporal behaviour of HH characterization by mean of means of HH, the mean of medians of HH, and the mean of PC80 of HH, indicated the HH can be classified to belong to three different groups for each one of these parameters. The impact of the system variables on temporal dynamics, explored using multiple regression procedure, indicated that the model for median was marginally better than mean. The CV was found to be most appropriate parameter to characterize the impact of GW system variable (aquifer type), a component of the system variables, on temporal dynamics. The interactions of GW (i) belonging to different GW system and (ii) at shoulder with footslope in a landscape were best characterized by simple linear correlations. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Very deep X-ray observations of the anomalous X-ray pulsar 4U 0142+614     

N. Rea  E. Nichelli  G. L. Israel  R. Perna  T. Oosterbroek  A. N. Parmar  R. Turolla  S. Campana  L. Stella  S. Zane  L. Angelini 《Monthly notices of the Royal Astronomical Society》2007,381(1):293-300

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A Bayesian periodogram finds evidence for three planets in HD 11964     

P. C. Gregory † 《Monthly notices of the Royal Astronomical Society》2007,381(4):1607-1616

A Bayesian multiplanet Kepler periodogram has been developed for the analysis of precision radial velocity data. The periodogram employs a parallel tempering Markov chain Monte Carlo algorithm. The HD 11964 data have been re-analysed using 1, 2, 3 and 4 planet models. Assuming that all the models are equally probable a priori, the three planet model is found to be ≥600 times more probable than the next most probable model which is a two planet model. The most probable model exhibits three periods of  38.02^+0.06_−0.05, 360⁺⁴₋₄ and 1924⁺⁴⁴₋₄₃ d  , and eccentricities of  0.22^+0.11_−0.22, 0.63^+0.34_−0.17 and 0.05^+0.03_−0.05  , respectively. Assuming the three signals (each one consistent with a Keplerian orbit) are caused by planets, the corresponding limits on planetary mass ( M sin  i ) and semimajor axis are     respectively. The small difference (1.3σ) between the 360-d period and one year suggests that it might be worth investigating the barycentric correction for the HD 11964 data.  相似文献   

Strong lensing statistics in large, z≲ 0.2, surveys: bias in the lens galaxy population     

Ole Möller  Manfred Kitzbichler  Priyamvada Natarajan 《Monthly notices of the Royal Astronomical Society》2007,379(3):1195-1208

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Mapping on the HEALPix grid     

Mark R. Calabretta  Boudewijn F. Roukema 《Monthly notices of the Royal Astronomical Society》2007,381(2):865-872

The natural spherical projection associated with the Hierarchical Equal-Area and Isolatitude Pixelization (HEALPix) is described and shown to be one of a hybrid class that combines the cylindrical equal-area and Collignon projections, not previously documented in the cartographic literature. Projection equations are derived for the class in general and are used to investigate its properties. It is shown that the HEALPix projection suggests a simple method of (i) storing and (ii) visualizing data sampled on the grid of the HEALPix pixelization, and also suggests an extension of the pixelization that is better suited for these purposes. Potentially useful properties of other members of the class are described, and new triangular and hexagonal pixelizations are constructed from them. Finally, the standard formalism is defined for representing the celestial coordinate system for any member of the class in the FITS data format.  相似文献   

Fitting sinusoids to observations of rotating spotted stars     

Chris Koen 《Monthly notices of the Royal Astronomical Society》2007,376(1):233-247

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Preliminary Studies on Predicting the Tropical Indian Ocean Sea Surface Temperature through Combined Statistical Methods and Dynamic ENSO Prediction          下载免费PDF全文

WANG Li-Wei  ZHENG Fei  ZHU Jiang 《大气和海洋科学快报》2013,6(1):52-59

The sea surface temperature(SST) in the Indian Ocean affects the regional climate over the Asian continent mostly through a modulation of the monsoon system.It is still difficult to provide an a priori indication of the seasonal variability over the Indian Ocean.It is widely recognized that the warm and cold events of SST over the tropical Indian Ocean are strongly linked to those of the equatorial eastern Pacific.In this study,a statistical prediction model has been developed to predict the monthly SST over the tropical Indian Ocean.This model is a linear regression model based on the lag relationship between the SST over the tropical Indian Ocean and the Ni o3.4(5°S-5°N,170°W-120°W) SST Index.The predictor(i.e.,Ni o3.4 SST Index) has been operationally predicted by a large size ensemble El Ni o and the Southern Oscillation(ENSO) forecast system with coupled data assimilation(Leefs_CDA),which achieves a high predictive skill of up to a 24-month lead time for the equatorial eastern Pacific SST.As a result,the prediction skill of the present statistical model over the tropical Indian Ocean is better than that of persistence prediction for January 1982 through December 2009.  相似文献   

Recent Near-surface Temperature Trends in the Antarctic Peninsula from Observed,Reanalysis and Regional Climate Model Data     

Deniz BOZKURT  David HBROMWICH  Jorge CARRASCO  Keith MHINES  Juan Carlos MAUREIRA  and Roberto RONDANELLI 《大气科学进展》2020,37(5):477-493

This study investigates the recent near-surface temperature trends over the Antarctic Peninsula.We make use of available surface observations,ECMWF’s ERA5 and its predecessor ERA-Interim,as well as numerical simulations,allowing us to contrast different data sources.We use hindcast simulations performed with Polar-WRF over the Antarctic Peninsula on a nested domain configuration at 45 km(PWRF-45)and 15 km(PWRF-15)spatial resolutions for the period 1991?2015.In addition,we include hindcast simulations of KNMI-RACMO21P obtained from the CORDEX-Antarctica domain(~50 km)for further comparisons.Results show that there is a marked windward warming trend except during summer.This windward warming trend is particularly notable in the autumn season and likely to be associated with the recent deepening of the Amundsen/Bellingshausen Sea low and warm advection towards the Antarctic Peninsula.On the other hand,an overall summer cooling is characterized by the strengthening of the Weddell Sea low as well as an anticyclonic trend over the Amundsen Sea accompanied by northward winds.The persistent cooling trend observed at the Larsen Ice Shelf station is not captured by ERA-Interim,whereas hindcast simulations indicate that there is a clear pattern of windward warming and leeward cooling.Furthermore,larger temporal correlations and lower differences exhibited by PWRF-15 illustrate the existence of the added value in the higher spatial resolution simulation.  相似文献   

江西省近50年霾天气时空分布特征及成因分析     

蒋璐君  刘熙明  张弛 《气象》2020,46(5):695-704

利用1964—2013年江西省83个站逐日霾观测资料,运用线性倾向估计等统计方法,分析江西省近50年霾时空变化特征及其与气候要素的关系。结果表明:江西霾日数呈赣中北部多、赣南少的特点,赣中的萍乡—宜春—抚州—上饶一带以及赣北北部的九江中部、景德镇北部地区是霾天气多发区,年均霾日数在30 d·a~(-1)以上。冬季霾日数最多,萍乡—宜春—鹰潭地区中北部、南昌—九江的中部以及上饶东部地区超过20 d·a~(-1),春季和秋季次之,夏季最少。12月是霾日数最多的月份,接近全年霾日数的2成。江西省霾日数呈年际增长的趋势,增长率为11 d·(10 a)~(-1),气候趋势系数为0.78,通过0.01的显著性水平检验。霾日数与平均风速和大风日数均呈负相关,而与静风日数呈正相关。近50年平均风速和大风日数呈下降趋势,静风日数呈上升趋势,这可能导致空气中污染物不易扩散而形成更多的霾天气。江西省降水日数呈减少趋势[-6.3 d·(10a)~(-1)],气温呈增暖趋势[0.15℃·(10a)~(-1)],霾日数与气温和降水日数分别呈正、负相关。  相似文献