Spatial and temporal aspects of phytoplankton blooms in complex ecosystems off the korean coast from satellite ocean color observations     

Yu -Hwan Ahn  Palanisamy Shanmugam  Kyung- Il Chang  Jeong -Eon Moon  Joo -Hyung Ryu 《Ocean Science Journal》2005,40(2):67-71

Complex physical, chemical and biological interactions off the Korean coast created several striking patterns in the phytoplankton blooms, which became conspicuous during the measurements of ocean color from space. This study concentrated on analyzing the spatial and temporal aspects of phytoplankton chlorophyll variability in these areas using an integrated dataset from a Sea-viewing Wide Field-of-view Sensor (SeaWiFS), Advanced Very High Resolution (AVHRR) sensor, and Conductivity Temperature Depth (CTD) sensor. The results showed that chlorophyll concentrations were elevated in coastal and open ocean regions, with strong summer and fall blooms, which appeared to spread out in most of the enclosed bays and neighboring waters due to certain oceanographic processes. The chlorophyll concentration was observed to range between 3 and 54 mg m^-3 inside Jin-hae Bay and adjacent coastal bays and 0.5 and 8 mg m^-3 in the southeast sea offshore waters, this gradual decrease towards oceanic waters suggested physical transports of phytoplankton blooms from the shallow shelves to slope waters through the influence of the Tsushima Warm Current (TWC) along the Tsushima Strait. Horizontal distribution of potential temperature (θ) and salinity (S) of water off the southeastern coast exhibited cold and low saline surface water (θ<19°C; S<32.4) and warm and high saline subsurface water (θ>12°C; S>34.4) at 75dBar, corroborating TWC intrusion along the Tsushima Strait. An eastward branch of this current was called the East Korean Warm Current (EKWC), tracked with the help of CTD data and satellite-derived sea surface temperature, which often influenced the dynamics of mesoscale anticyclonic eddy fields off the Korean east coast during the summer season. The process of such mesoscale anticyclonic eddy features might have produced interior upwelling that could have shoaled and steepened the nutricline, enhancing phytoplankton population by advection or diffusion of nutrients in the vicinity of Ulleungdo in the East Sea.  相似文献   

Three-dimensional hydrodynamic-eutrophication model (HEM-3D): application to Kwang-Yang Bay, Korea   总被引：9，自引：0，他引：9  

Park K  Jung HS  Kim HS  Ahn SM 《Marine environmental research》2005,60(2):171-193

The purpose of this paper is twofold: to describe the water quality model of Three-Dimensional Hydrodynamic-Eutrophication Model (HEM-3D) and to present an application of HEM-3D to a coastal system in Korea. HEM-3D, listed as a tool for the development of Total Maximum Daily Load by US Environmental Protection Agency, is a general-purpose modeling package for simulation of the flow field, transport, and eutrophication processes throughout the water column and of diagenetic processes in the benthic sediment. This paper describes the water quality model of HEM-3D with emphasis on its unique features. Excessive loadings of organic wastes have significantly deteriorated water quality conditions of Korean coastal waters. This paper presents an application of HEM-3D to Kwang-Yang Bay, a coastal system in Korea, which is one of the first water quality modeling efforts for Korean coastal waters accompanied by a relatively comprehensive field program. The current status of data availability for water quality modeling in Korea is discussed.  相似文献   

Operational Implementation of the ATOVS Processing Procedure in KMA and Its Validation   总被引：1，自引：0，他引：1  

Myoung-Hwan AHN  Mee-Ja KIM  Chu-Yong CHUNG  Ae-Sook SUH 《大气科学进展》2003,20(3):398-414

The Korea Meteorological Administration (KMA) has processed the data from the advanced TOVS(ATOVS) onboard NOAA-16 satellite since May 2001. The operational production utilizes the AAPP(ATOVS and AVHRR Processing Package) of EUMETSAT and IAPP (International ATOVS ProcessingPackage) of the University of Wisconsin. For the initial guess profiles, the predicted fields (usually 6 to 12hour forecasted fields) from the global aviation model of NOAA/NCEP are used. The average number ofprofiles retrieved from the ATOVS data is about 1,300 for each morning and afternoon orbit at about 18 and06 UTC, respectively. The retrieved temperature and dew point temperatures are provided to forecastersin real time and used for initialization of prediction models. With the advanced microwave sensor (AMSU;Advanced Microwave Sounding Unit), accuracy of the ATOVS products is expected to be better than thatof the TOVS products, especially in cloudy conditions. Indeed, the preliminary results from a validationstudy with the collocated radiosonde data during a 8-month period, from May to December 2001, for theEast Asia region show an improved accuracy of the ATOVS products for cloudy skies versus the TOVS,especially for higher altitudes. The RMS (Root Mean Square) difference between the ATOVS productsand radiosonde data is about 1.3℃ for both clear and cloudy conditions, except for near the ground and athigher altitudes, at around 200 hPa. There is no significant temporal variation of the error statistics at allpressure levels. In case of the water vapor mixing ratio, the largest difference is shown at lower altitudes,while the accuracy is much better for the clear sky cases than the cloudy sky cases. The bias and RMSEat lower altitudes is about 0.557 g kg-1 and 2.5 g kg-1 and decrease significantly with increasing altitude.  相似文献   

Formation mechanisms of illite,chlorite and mixed-layer illite-chlorite in Triassic volcanogenic sediments from the Southland Syncline,New Zealand     

Jung Ho Ahn  Donald R. Peacor  Douglas S. Coombs 《Contributions to Mineralogy and Petrology》1988,99(1):82-89

Clay minerals from the three principal kinds of zeolitic sediments from the type area for zeolite facies alteration, the Triassic Murihiku Supergroup, Southland, New Zealand, have been studied by TEM. Bentonitic tuff consists largely of smectite and heulandite with minor illite; they occur as replacements of glass shards and are inferred to be direct alteration products of tuff alteration. Both analcime- and laumontite-rich tuffs contain chlorite, illite and mixed-layer illite-chlorite, including 11 mixed-layer sequences. Subhedral to euhedral phyllosilicate crystal shapes and other textural features imply that phyllosilicates crystallized from solution derived in part by dissolution of precursor smectite. Intralayer transitions involving illite and chlorite are inferred to be products of crystallization rather than direct alteration and replacement. Petrographically similar bentonitic and analcimized tuffs overlap each other in the stratigraphic section, supporting earlier observations that there is no systematic change in smectite relative to the illite plus chlorite derived from smectite in sections up to 8.5 km thick. The data imply that smectite may be metastable relative to illite plus chlorite. Permeability and fluid chemistry are inferred to be as significant as temperature in promoting reactions in clay minerals as well as zeolites during burial metamorphism.Contribution No. 436, from The Mineralogical Laboratory, Department of Geological Sciences, The University of Michigan, Ann Arbor, Michigan 48109  相似文献   

Added mass and damping of horizontal circular cylinder sections     

M. Greenhow  S.I. Ahn 《Ocean Engineering》1988,15(5)

This note brings together and extends previously known results for the added masses and dampings of surface-piercing or completely submerged horizontal circular cylinders. For vertical (heave) motions, but not horizontal (sway) motions, a striking qualitative change occurs in these hydrodynamic coefficients when the cylinder breaks the surface. This is simply explained in terms of low-frequency asymptotics and the equivalent wavemaker method.  相似文献   

Analytic hierarchy models for regional groundwater monitoring well allocation in Southeast Asian countries and South Korea     

Gyoo-Bum Kim  Joo-Sung Ahn  Atsunao Marui 《Environmental Earth Sciences》2009,59(2):325-338

Groundwater has played an important role in economic development in Southeast Asian countries, but some problems caused by nature or human actions such as contamination, over pumping, and land subsidence bring the necessity of more systematic groundwater monitoring wells. The analytical hierarchy process with pairwise comparison was used to allocate and organize the regional groundwater monitoring wells in five regions, Thailand, Cambodia, East/West Malaysia, and South Korea. Five different multi criteria decision models, which were composed of three primary criteria and eight secondary criteria, were developed based on the answers of the questionnaire from 76 groundwater experts in Thailand, 100 in Cambodia, 101 in East Malaysia, 87 in West Malaysia, and 93 in South Korea. It was revealed that the weights of model criteria for each country, which also represent relative importance on groundwater monitoring, were different according to the diverse groundwater situation. The most important factor to determine the number of monitoring well was ‘number of households using only groundwater as a water source’ for Thailand and South Korea, ‘number of contamination sources’ for Cambodia, ‘amount of groundwater use for drinking-water supply’ for East Malaysia, and ‘number of wells with contaminated water’ for West Malaysia.  相似文献   

MgO‐Based Binder for Treating Contaminated Sediments: Characteristics of Metal Stabilization and Mineral Carbonation          下载免费PDF全文

Kyung‐Yup Hwang  Jeong‐Yun Seo  Hoang Q. H. Phan  Jun‐Young Ahn  Inseong Hwang 《洁净——土壤、空气、水》2014,42(3):355-363

  相似文献   

Use of a nonstationary copula to predict future bivariate low flow frequency in the Connecticut river basin   总被引：1，自引：0，他引：1       下载免费PDF全文

Kuk‐Hyun Ahn  Richard N. Palmer 《水文研究》2016,30(19):3518-3532

Frequency analysis of streamflow provides an essential ingredient in our understanding of hydrologic events and provides needed guidance in the design and management of water resources infrastructure. However, traditional hydrologic approaches often fail to include important external effects that can result in unpredictable or unforeseen changes in streamflow. Moreover, previous studies investigating multiple characteristics of streamflow do not address a nonstationary approach. This study explores nonstationary frequency analysis of bivariate characteristics, including occurrence and severity, of annual low flow in the Connecticut River Basin, United States. To investigate bivariate low flow frequency, copulas and their marginal distributions are constructed by using stationary and nonstationary approaches. Our study results indicate that streamflow used in this study demonstrate significant nonstationarity. Over time, the occurrence and severity of low flows are shown to be lower with the same probability based on the results of nonstationary copulas. Bivariate low flow frequencies in the years 1970, 2000, and 2030, and their joint return periods are estimated under the nonstationary copulas. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Photometric observations of NY Cephei     

Young Shuk Ahn 《Astrophysics and Space Science》1992,198(1):137-148

NewUBV photoelectric observations of NY Cep were made from 1982 to 1989 with GOTO 61-cm telescope at the Yonsei University Observatory. Seven times of minimum light were obtained. An improved orbital period of 15.27566 day was determined. The light curves were analyzed using the Wilson-Devinney method. It is confirmed that NY Cep is a detached system and the absolute dimensions are also obtained. It is found that the secondary eclipse does not occur due to large eccentricity and inclination.  相似文献   

Gyroless attitude estimation of sun-pointing satellites using magnetometers   总被引：2，自引：0，他引：2  

Hyo-Sung Ahn Seon-Ho Lee 《Geoscience and Remote Sensing Letters, IEEE》2005,2(1):8-12

Deterministic attitude estimation methods based on vector observations are used for the coarse-attitude calculation of the sun-pointing satellites. The objective of the deterministic attitude estimation is to get the direction cosine matrix without considering the stochastic noises. The existing deterministic attitude estimation methods require two complete (three-axis) vector observations corresponding to two known reference vectors. This letter suggests a new deterministic attitude estimation method using only geomagnetic-field measurements on two axes for sun-pointing satellites in the sun-acquisition mode.  相似文献