高空大尺度温度“湍流”输送对高度倾向影响的个案研究     

顾震潮 《气象学报》1959,30(2):191-194

本文用正压模式计算了大尺度湍流输送项对高度倾向的影响,用的是1956年2月13—22日的资料.在这例子中涡度的湍流输送的项作用与平均输送项大小量级相同.这两项所造成的高度倾向分布颇不相同,并不成简单的此例关系.  相似文献   

Effects of Non-orographic Gravity Wave Drag on Seasonal and Medium-range Predictions in a Global Forecast Model     

Hyun-Joo Choi  Ji-Young Han  Myung-Seo Koo  Hye-Yeong Chun  Young-Ha Kim  Song-You Hong 《Asia-Pacific Journal of Atmospheric Sciences》2018,54(1):385-402

This study implements the parameterizations of convective and frontal gravity wave drag (GWD) with wide phase speed spectra into a global forecast model with a model top near 0.3 hPa. The new convective GWD scheme replaces the existing one that considers only a stationary convective GW, and the frontal GWD scheme is newly introduced. When the new GWD schemes are used, the Rayleigh friction, applied above 2 hPa to mimic the effects of missing GWD, is removed. The convective (frontal) GWs are generated mainly in the Intertropical Convergence Zone and winter extratropical storm track regions (extratropics where strong baroclinicity exists). The convective and frontal GWD derived from the new schemes are significant near the model top, with maxima of ~2-4 and ~26-58 m s^?1 day^?1, respectively. The differences in convective GWD between the stationary and non-stationary schemes appear mainly in the tropics and summer hemisphere, where stationary GWs cannot propagate upward. The new schemes improve the seasonal representation of stratospheric wind, through changes in both the GWD and the resolved wave forcing, which is modulated by the changed large-scale wind due to the GWD. The downward influence, in response to the changed GWD, is also positive in the tropospheric fields, such as subtropical jet and planetary-scale disturbances. For the medium-range forecasts, improved skill scores on wind speed are achieved globally with the new schemes. The improvements mostly appear only in the stratosphere during the early forecast period (~3 days) but expand to the troposphere as forecast time increases.  相似文献   

Flow and transport modeling in the sea-breeze part II: Flow model application and pollutant transport   总被引：2，自引：0，他引：2  

Youn-Seo Koo  Danny D. Reible 《Boundary-Layer Meteorology》1995,75(3):209-234

A modifiedE- non-hydrostatic model with non-equilibrium level 2.5 closure was applied to the flow and pollutant dynamics in the sea-breeze. The model predicts key observed characteristics of the sea-breeze, such as midday slowing of inland penetration, fast and deep inland penetration in late afternoon, and detachment of the sea-breeze from the feeding flow in early evening. In late evening when the turbulent mixing over the land subsides due to the surface cooling, a frontal density current is formed and the predicted structure is in good agreement with observations and laboratory experiments of density currents. Turbulent mixing over the land is a key parameter that controls midday slowing and late afternoon frontal development.The calculated thermal internal boundary layer and fumigation of an elevated line source show good agreement with observations and similarity theory. Calculations suggest that the residual plume aloft over the sea returns onshore at ground level during the afternoon sea-breeze and has a large impact on ground-level concentrations during the following day.  相似文献   

Three unrecorded marine fish species from Korean waters     

Jeong -Ho Park  Jin Koo Kim  Jee Hwan Moon  Cheol Bum Kim 《Ocean Science Journal》2007,42(4):231-240

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Changes in benthic communities along a presumed pollution gradient in Vancouver Harbour     

Je JG  Belan T  Levings C  Koo BJ 《Marine environmental research》2004,57(1-2):121-135

Samples of macrobenthic organisms were obtained at seven stations on a presumed pollution gradient from the head of Vancouver Harbour through to outer Howe Sound. Polychaetes (83 apparent species) and molluscs (43 apparent species) were the most abundant faunal groups numerically (44.8 and 47.9%, respectively). Molluscs accounted for most of the biomass (87.9%). The following univariate and multivariate methods were used to investigate structural changes in the benthic communities: ANOVA, Abundance-Biomass Comparisons and related statistics, cluster analysis, multidimensional scaling, and the BIOENV procedure. Most of the analyses divided the seven stations into three groups: Port Moody Arm (Inner Harbour): two stations; Inner and Outer Harbour: four stations, and Gibsons (Howe Sound): one station. Further cause-effect investigations are needed to determine the sensitivity to organic pollution of indicator species identified in the survey. However our data correlating benthic community changes to sediment chemistry suggest the inner harbour was dominated by pollution-tolerant species. Depth and sediment grain size were confounding factors for the interpretations.  相似文献   

The effect of nonlinear multi-contact coupling with gap between risers and guide frames on global spar motion analysis   总被引：1，自引：0，他引：1  

B. J. Koo  M. H. Kim  R. E. Randall 《Ocean Engineering》2004,31(11-12):1469-1502

Nonlinear multi-contact coupling between vertical risers and guide frames inside the spar moon-pool is studied. The existing numerical model for hull/mooring/riser coupled dynamics analysis treats riser as an elastic rod truncated at the keel (truncated riser model), and the risers are free to slide in vertical direction with constant tension, while restricted in horizontal direction. The truncated riser model neglects the portion of the riser inside the moon-pool and tends to overestimate the spar pitch motion. In the newly developed model, the risers are extended through the moon-pool with realistic boundary conditions at multiple guide frames, and thus additional contact forces and moments on the spar hull are considered. The gap effects between the riser buoyancy-cans and riser guide frames are also modeled using three different types of gap springs. Their different dynamic characteristics are extensively studied. The new riser model also considers the Coulomb damping between buoyancy-cans and riser guide frames and also allows the impact-like contact force calculation on risers for ensuring fatigue analysis.  相似文献   

Pattern and origin of spherulites in a rhyolite dike swarm,northeastern Cheongsong, Korea     

Sang Koo Hwang  Chang Oh Choo 《世界地质(英文版)》2006,9(1)

Several NNW-trending Cretaceous rhyolite dikes in the northeastern Cheongsong area of southern Korea contain spherulitic fabrics and are locally quarried as an ornamental stone. The dikes, part of the Cheongsong dike swarm, contain a variety of spherulites which are characterized by radial array of acicular intergrowths from fibrous quartz and alkali feldspars. They are classified as some simple, multiple and compound spherulite types from flower-like patterns, and the types are different each other in spatial distribution within the dikes. The various radial fabrics suggest that they crystallized under the different cooling mechanisms and processes in rapidly cooling dikes. Spheroids lacking a flower-like pattern may be precipitated after compositional segregation in a supercooled magma. Simple acicular spherulites could be crystallized by devitrification of true glass which cooled rapidly below the transformation temperature, whereas layered multiple spherulites could result from a crystallization of supercooled magma at relatively rapid cooling rates above the transformation temperature. Acicular multiple spherulites could be produced from a combination of the above three mechanisms operating at slower cooling rates.  相似文献   

Stable Isotopic Composition for Hydrothermal Vein Deposits, Southeastern Korea     

Kim Sang Jung  Lee Hyun Koo 《中国地质大学学报(英文版)》2000,11(2)

The southeastof Korea has attracted considerable atten-tion in the geologic community because of its extensive ig-neous activity and associated mineralizations from the L ateCretaceous to the Early Tertiary (Cu,Pb- Zn,W- Mo,Bi andAu- Ag hydrotherm al- vein deposits,porphyry,skarn and al-tered clay deposits) .The southeast of Korea is composed ofCretaceous sedimentary Gyeongsan basin,volcanic and plu-tonic rocks.Most of the m ines are either closed or incapableof producing more ores becau…  相似文献   

Spatio‐Temporal Variations in Stream–Aquifer Interactions Following Construction of Weirs in Korea          下载免费PDF全文

Hyeonju Lee  Min‐Ho Koo  Kisu Kim  Yongcheol Kim 《Ground water》2016,54(3):448-458

The “Four Major Rivers Restoration Project” was conducted to secure sufficient water resources, introduce comprehensive flood control measures, improve water quality, and restore river ecosystems in Korea. As a part of the project, 16 sites were dredged and weirs were installed in the Han, Geum, Yeongsan, and Nakdong Rivers from late 2010 to early 2012. Groundwater data were obtained from 213 groundwater monitoring wells near the four major rivers to analyze the impacts of weir construction on the nearby groundwater flow system. The groundwater level and chemical characteristics were analyzed to investigate how the groundwater flow system and water quality changed following weir construction. Our results show that the groundwater level immediately increased with increased river levels following weir construction. In addition, the hydrologic condition of some rivers upstream of the weirs was changed from gaining to losing streams. Consequently, the direction of groundwater flow changed from perpendicular to parallel to the river, and groundwater downstream of the weir became recharged from the area upstream of the weir. This should affect groundwater quality, which should become similar to the river water; however, this change has not yet been observed. Therefore, both further monitoring of the groundwater quality and further hydrogeochemical analysis are required for quantitative evaluation of the effects of weir construction in the study area.  相似文献   

Sand–mud couplets deposited by spontaneous remobilization of subaqueous transitional flows     

Woong Mo Koo  David Mohrig  James Buttles  Daniel Sturmer  Anna Pontén  Thomas Hess 《Sedimentology》2020,67(1):78-95

Clean basal and capping argillaceous sandstone couplets in deep water settings have been previously interpreted as the result of spatially segregated turbidity currents and debris flows or spatio-temporal transitioning of a turbulent flow to a transitional/laminar state. However, this paper presents three-dimensional laboratory experiments demonstrating that a single sediment-gravity flow can develop sand–mud couplets by autogenic remobilization of sediments that are still in the process of being deposited. This remobilization appears common to flows composed of mixtures of sand and mud with viscosities and strengths measurably greater than water, but not so high as to fully suppress the settling of sand through the depositional current. Dewatering in the early sand deposit acts to lubricate the basal portion of the increasingly muddy upper division of the flow, causing it to accelerate downslope, triggering a secondary flow with a sediment composition distinct from the original mixture. Sediment deposition and remobilization processes in a single sediment-gravity flow and their resultant deposit were imaged acoustically and cored at representative locations within the deposit. The acoustic data and cores show sand–mud couplets that are qualitatively similar to interpreted turbidite–debrite-like couplets in natural systems.  相似文献