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101.
102.
Peter Rhines 《地球物理与天体物理流体动力学》2013,107(3-4):273-302
Abstract It is found that in a rotating stratified fluid bounded by a single rigid wall, edge waves may occur at all frequencies less than or equal to N sin a (a is the angle of the wall from the horizontal and N the Brunt‐Vaisala frequency). These decay exponentially away from the boundary, in a distance of O(S) wavelengths, for α = O(1), or O(S ‐1) wavelengths, for αS ≤ O(1), where S is the ratio of N to the Coriolis parameter f, taken for illustration to be large. The phase and energy both move with a component to the left, facing shallow water. The waves could, for example, appear as an internal tide at the continental rise or as baroclinic meandering of currents over a slope. The low‐frequency limit, αS ? 1, is studied in detail. To allow for large scales of motion other rigid boundaries and variations in f are included. The edge (actually “bottom") waves then merge with topographic‐planetary waves as the wavelengths increase; the familiar depth‐independent mode is found to be possible in the sea for wavelengths exceeding about 450 km. The ß‐effect introduces modes complementary to that trapped at the bottom, which instead are isolated from it. 相似文献
103.
Snow is an important component of the earth's environment, and can significantly impact the everyday life of those living in a large portion of the United States. However, accurate and complete information on snowfall and snow cover is presently being collected at only 57% of the official climate observing stations in states where regional snows occur on an annual basis. The quality of the data varies significantly from one state to another, although it tends to be weakest where snow is least common. As a result of this evaluation, the list of stations with daily snow data published in National Oceanic and Atmospheric Administration Climatohgical Data publications has been revised and expanded. [Key words: snow, snow observations, climate data, United States.] 相似文献
104.
Mustafa Softa Tahir Emre Hasan Sözbilir Joel Q. G. Spencer Mehmet Turan 《Geodinamica Acta》2018,30(1):249-264
The Eastern Pontides (EP), which is the under transpressional deformation zone, is an active mountain belt that has been rising rapidly since the Cenozoic era because of the Arabian-Eurasian convergence. Morphometric studies have been performed to investigate the tectonic activity of this region and better understand the characteristics of the faults geomorphologically; the faults control the mountain fronts in the drainage basin of the EP. The results show the Hypsometric Curve (HC)-Hypsometric Integral (0.37-HI-0.67), Basin-Shaped Analysis (1.2-Bs-7), Valley-Floor-Width to Height-Ratio (0.4-Vf-1.2) and Asymmetry Factor (35-AF-81) applied to 46 drainage basins together with 9 tectonically controlled geomorphic indices (1.2-Smf-1.5) and a Stream Length Gradient (30-SL-120) indicate that the EP is tectonically active, and when the areas are evaluated according to Smf and Vf analyses, the tectonic level is relatively high. According to our conceptual model for the uplifting of the EP, with respect to field studies and morphometric analysis, (i) the EP is the active deformation zone and has a “push-up” geometry in conjunction with the North Anatolian Fault; (ii) the EP is progressively uplifting at a rate of more than 0.5 mm/yr in along with the thrust faults of the Black Sea Fault (BSF) and Borjomi-Kazbegi Fault (BKF). 相似文献
105.
The Galileo spacecraft explored Jupiter’s magnetotail in a low-inclination orbit, where it detected the signatures of tail reconnection. In this paper, we examine and classify the tail reconnection signatures into four types: dipolarizations, strong northward Bθ excursions, tailward-moving plasmoids and planetward-moving plasmoids. The distribution of these four types of events is used to infer the most probable location of the Jovian tail reconnection site to be near 0200 LT at a planetocentric distance of 80 Jovian radii. Dipolarizations are mainly observed planetward of this point, and strong northward Bθ excursions and plasmoids are found mostly tailward. The observations also suggest that the Jovian tail reconnection starts at a point (neutral point), a localized region in the tail, instead of along an extended azimuthal line (X-line). Using the updated Khurana’s Jupiter’s magnetospheric model, which includes the external field and the effects of the swept-back configuration of tail field lines, we map the signatures of Jovian tail reconnection into the Jupiter’s ionosphere. We confirm that the dawn auroral storms or the polar dawn spots observed by the Hubble Space Telescope (HST) are located close to the extrapolated footpoints of tail dipolarizations and could be the auroral signatures of tail reconnection. 相似文献
106.
水团对吕宋海峡浮游植物群落结构的影响 总被引:2,自引:0,他引:2
根据2008年8月18日至9月19日在吕宋海峡3个断面获得的0~200 m层浮游植物数据,探讨了群落结构及其与不同理化性质水团的关系。本研究共鉴定浮游植物4门61属169种(包括变种、变型和未定种),其中甲藻和硅藻物种数基本相当,各占所有物种数的50%左右;另记录了金藻门3属3种;蓝藻门1种。海区优势种为卡氏前沟藻Amphisdinium carterae、锥状施克里普藻Scrippsiella trochiodea、角毛藻Chaetoceros sp.和原甲藻Prorocentrum sp.。丰度范围是(0.08~9.48)×106个/m3,平均为1.448×106个/m3。甲藻占总细胞丰度的74.68%;硅藻占24.96%。在水平方向,B断面和C5站浮游植物丰度较高,甲藻主要分布于远离陆地的海峡中部,而硅藻主要分布于台湾岛和吕宋岛附近;浮游植物垂直分布主要在水体的0~50 m层。聚类分析并结合水文数据表明浮游植物基本可划分为3个类群,分别受南海水、黑潮水和混合水的影响。南海水与黑潮水交汇的锋面区域,具有较周围区域更高的物种数、水柱平均丰度及硅甲藻丰度比,体现出强烈的锋面效应。 相似文献
107.
Thermal and haline fronts in the Yellow/East China Seas: Surface and subsurface seasonality comparison 总被引:1,自引:0,他引:1
Seasonal variability of surface and subsurface thermal/haline fronts in the Yellow/East China Seas (YES) has been investigated
using three-dimensional monthly-mean temperature and salinity data from U.S. Navy’s Generalized Digital Environmental Model
(Version 3.0). The density-compensated Cheju-Yangtze Thermal/Haline Front has (northern and southern) double-tongues. The
northern tongue is most evident throughout the depth from December to April. The southern tongue is persistent at the subsurface
with conspicuous haline fronts. The thermal (haline) frontal intensity of the northern tongue is controlled mainly by the
temperature (salinity) variation on the shoreward (seaward) side of the front. The cold water over the Yangtze Bank is influential
in generating the southern tongue and intensifying the Tsushima Thermal Front. The year-round Cheju-Tsushima Thermal Front
is evident throughout the depth and intensifies from July to December. The northern arc of the Yangtze Ring Haline Front is
manifest in spring and is sustained until summer, whereas the southern one is fully developed in summer because of eastward
migration of the Yangtze Diluted Water. The area showing strong frontal intensity in the Chinese Coastal Haline Front shifts
seasonally north and south along the Zhejiang-Fujian coast. The Generation and evolution of YES fronts are closely associated
with YES circulation (inferred from the linkage of the water masses). Moreover, the subsurface temperature/salinity evolution
on the fronts in the Yellow Sea differs from that in the East China Sea owing to local factors such as wintertime vertical
mixing and a summertime strong thermocline above the Yellow Sea Bottom Cold Water. 相似文献
108.
109.
110.
基于引力模型的海洋锋信息提取 总被引:2,自引:0,他引:2
海洋锋面是海洋水团特性明显不同的两种或几种水体之间的狭窄过渡带。本文旨在对遥感反演海洋温度场数据(SST),引入引力模型进行海洋锋面的检测。鉴于海洋锋受噪声干扰大,锋面强度小的特点,本文提出了基于引力算法的引力模型。其中,引力算法是将温度数据中的每一个像元点都作为一个独立的天体,其质量对应该像元的温度值,根据引力定律计算3×3区域中,邻域像元对中心点像元的引力和。模型首先对原始数据进行去0处理,为消除对原始数据明暗程度的依赖,对3×3区域数据进行归一化,然后利用函数对归一化后的数据进行增强处理,最后,以引力算法进行锋面检测。验证表明,该模型能有效强化不同区域或水体差异性,并能够有效针对海洋锋信息进行提取,受噪声影响小。 相似文献