Home range and elevated egg densities within an inshore spawning ground of coastal cod     

Espeland  Sigurd Heiberg; Gundersen  Ailin Fernlof; Olsen  Esben Moland; Knutsen  Halvor; Gjosaeter  Jakob; Stenseth  Nils C. 《ICES Journal of Marine Science》2007,64(5):920-928

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西沙群岛附近海域船舶尾迹水体遥感反射率特性的实验测量与分析     

张宇  张永刚  王华 《热带海洋学报》2007,26(2):22-25

利用海上实验现场测量船舶的尾迹气泡群对西沙群岛附近海域一类水体海水光学特征(例如归一化离水辐亮度、遥感反射率)的影响,为通过星载光学传感器遥感获取船舶尾迹信息提供理论依据。实验证明,在可见光和近红外波段,船舶含气泡尾迹不仅在幅度上、也在谱形上改变海水遥感反射率,作为结果,尾迹气泡使得海水变得更绿;同时,随着观测点在尾迹中的位置距目标船的接近,气泡密度不断增大,反射率也随之增强。  相似文献   

MtDNA and microsatellite variation in Baltic Atlantic salmon   总被引：5，自引：0，他引：5  

Nilsson  J. 《ICES Journal of Marine Science》1997,54(6):1173-1176

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2019年北京市PM2.5人群暴露剂量特征分析     

林金煌  陈文惠  张岸 《地球信息科学学报》2020,22(12):2348-2357

近年来,PM_2.5已成为雾霾爆发的主要污染物之一,人口长期暴露在高浓度的PM_2.5中可能会大大的提高居民患病的几率,危害居民身心健康。本研究以空气污染严重且人口高度集中的北京市作为研究区,以2019年北京市的PM_2.5浓度监测数据、人口空间分布栅格数据及不同人群的长期呼吸量等为数据基础,构建了“污染物浓度—暴露人口—呼吸量”的PM_2.5人口暴露剂量评估模型,进而对北京市2019年的PM_2.5人口暴露强度空间分异特征及不同人群的暴露剂量差异进行分析。结果表明：① 2019年北京市的PM_2.5浓度在冬季时最高,日均浓度达48.89 μg/m³,并均呈现出北低南高的整体态势;② PM_2.5人口暴露量存在显著的空间分异特征,不同人群的PM_2.5暴露量均呈现出由城中心向周边减弱的整体态势,高暴露区主要集中于城区地带;③ 不同性别、年龄组人群的PM_2.5人口暴露强度存在明显的空间分异特征,且城市内部不同人群的PM_2.5暴露剂量也存在明显差异;④ PM_2.5的暴露风险并非完全取决于污染物浓度的大小,而是由污染源浓度和暴露受体的空间分布特征等多方面共同决定,北京城区的高PM_2.5人口暴露区才是高风险区,是未来政府有效防控污染物危害的核心区。  相似文献   

塔克拉玛干沙漠夏季晴空对流边界层大涡模拟     

王敏仲  徐洪雄  王寅钧  买买提艾力&#  买买提依明  张建涛 《中国沙漠》2018,38(6):1275-1286

为了探索塔克拉玛干沙漠夏季晴空对流边界层湍流结构和热对流运动规律,利用沙漠腹地探空及地表通量观测资料,开展了晴空对流边界层的大涡模拟研究。结果表明：（1）沙漠夏季晴空条件下,对流边界层湍能主要由地表热力浮力对流产生,机械剪切对边界层湍能的贡献较小,小尺度湍涡对湍能的耗散随高度呈减弱趋势,边界层湍能变化呈现间歇性特点。（2）沙漠夏季晴空边界层中存在着有组织的热对流泡现象,热泡最大上升速度可超过4.0 m·s^-1;沙漠热对流运动一般呈羽状和网状分布特征,在上升运动区周围伴随有大片的下沉辐散区域。（3）地表感热和逆温层顶盖强度是控制和影响沙漠对流边界层发展的两个重要因素,感热增大,对流边界层变暖且高度升高;感热减小,对流边界层变冷且高度降低。在感热不变的条件下,逆温层顶盖强度越强,越不利于对流边界层发展,反之则相反。  相似文献   

The effective age of bubbles in polar ice     

I. G. Enting  J. V. Mansbridge 《Pure and Applied Geophysics》1985,123(5):777-790

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Mixture of populations     

Hua Zhu  André G. Journel 《Mathematical Geology》1991,23(4):647-671

A simple example simulating a mixture of two normal populations results in some important observations, nonnormality and nonsymmetry of the mixture conditional pdf, nonlinearity of the conditional mean as a function of the conditioning data, heteroscedasticity of the conditional variance and its nonmonotonicity as a function of distance of the unknown to the conditioning data. A comparison of the mixture statistics with those predicted by traditional models ignoring the mixture reveals the inadequacy and inappropriateness of these traditional approaches. A mixture of two multivariate normal populations is illustrated through the analytical expressions of its conditional distribution and moments.  相似文献   

Factors influencing the height of Hawaiian lava fountains: implications for the use of fountain height as an indicator of magma gas content   总被引：1，自引：1，他引：0  

E. A. Parfitt  L. Wilson  C. A. Neal 《Bulletin of Volcanology》1995,57(6):440-450

The heights of lava fountains formed in Hawaiian-style eruptions are controlled by magma gas content, volume flux and the amounts of lava re-entrainment and gas bubble coalescence. Theoretical models of lava fountaining are used to analyse data on lava fountain height variations collected during the 1983–1986 Pu'u 'O'o vent of Kilauea volcano, Hawaii. The results show that the variable fountain heights can be largely explained by the impact of variations in volume flux and amount of lava re-entrainment on erupting magmas with a constant gas content of 0.32 wt.% H₂O. However, the gas content of the magma apparently declined by 0.05 wt.% during the last 10 episodes of the eruption series and this decline is attributed to more extensive pre-eruption degassing due to a shallowing of the sub-vent feeder dike. It is concluded that variations in lava fountain height cannot be simply interpreted as variations in gas content, as has previously been suggested, but that fountain height can still be a useful guide to minimum gas contents. Where sufficient data are available on eruptive volume fluxes and extent of lava entrainment, greatly improved estimates can be made of magma gas content from lava fountain height.  相似文献   

长江、黄河、辽河水系中华绒螯蟹(Eriocheir sinensis)野生和养殖群体遗传变异的微卫星分析_*     

刘青  刘皓  吴旭干  邱高峰  何杰  董鹏生  成永旭 《海洋与湖沼》2016,47(1)

我国中华绒螯蟹(以下简称河蟹)养殖主要集中在长江、黄河和辽河流域, 经过多年的人工养殖、跨流域引种和增殖放流等活动可能会对其遗传特性造成一定的影响,因此本研究利用29个微卫星标记对3个水系的野生和养殖群体进行了遗传特征分析。结果表明：(1) 29个SSR标记共检测到943个等位基因,各位点等位基因数在11-52之间, 平均为32.52个; 各位点的平均观测和期望杂合度分别为0.723和0.876,仅5个位点处于Hardy-Weinberg平衡中;各位点平均多态信息含量(PIC)为0.864,其中28个为高多态性位点(PIC>0.5)。(2) 6个群体均表现出较高的遗传杂合度水平(H_O=0.702-0.744);香农信息指数(I,介于2.566-2.661)显示6群体的遗传多样性水平依次为：长江野生>长江养殖>黄河野生>辽河养殖>黄河养殖>辽河野生。(3)方差分析(AMOVA)结果显示,来源于种群内个体间和个体内部的变异分别为14.02%和85.88%,群体遗传分化指数F_ST仅为0.0008-0.0050,群体间的遗传分化处于较低水平(F_ST<0.05);基于Nei’s遗传距离的UPGMA聚类结果显示,长江野生群体单独聚为一支, 其余5群体共同聚为大一支, 其中长江养殖群体、黄河野生群体与黄河养殖群体聚为一小支,辽河野生群体和养殖群体聚为另一小支。(4) 瓶颈效应分析显示,所有群体近期均经历过有效种群的降低。群体遗传结构分析显示显示,6种群内个体的遗传组成混杂,不能根据其遗传结构划分出最佳理论群体数。综上所述,三水系野生和养殖群体均具有较高的遗传多样性,长江和黄河野生群体的遗传多样性略高于养殖群体;三水系河蟹野生群体的遗传分化与地理距离具有一定的相关性,长江养殖群体、黄河野生及养殖群体间的遗传分化较小可能与其跨流域引种及养殖群体逃逸造成其种质混杂有关。  相似文献   

Statistics of breaking waves and its applications to estimation of air-sea fluxes (I)--Theoretical models     

ZHANG Shuwen  Yuan Yeli 《中国科学D辑(英文版)》2004,47(1)

Wave breaking statistics, such as the whitecap coverage and average volume of broken seawater, are evaluated in terms of wave parameters by use of wave breaking model (Yuan et al., 1988) taking the fifth order Stokes's wave as the analog of the original wave field. Based on the observed fact that breaking waves play an important role in the exchange of mass, momentum and energy between the atmosphere and the ocean, the influence of wave breaking on air-sea fluxes of heat and moisture is investigated. Theoretical expressions of bubble-volume flux and sea spray spectrum at the sea surface and models for bubble-induced and spray droplet-induced heat and moisture fluxes are established. This work can be taken as the basis for further understanding the mechanism of air-sea coupling and parameterization models.  相似文献