• Korean Journal of Environmental Biology
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• v.27 no.4
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• pp.425-432
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• 2009

Mesozooplankton dynamics were studied in Watan stream which flows into the Yellow Sea in Yeonggwang, Korea. Samples were collected at eight stations bimonthly during April 2006~February 2007. Mesozooplankton community was consisted of 45 taxa (8 cladocerans and 29 cope-pods). The abundance varied between the highest one ($31{\sim}127,587\;indiv.m^{-3}$) in October, and the lowest ($12{\sim}233\;indiv.m^-3$) in December. Diversity index showed to be the highest value in July (0.671) and the lowest one in August (0.368). A euryhaline species, Acartia hongi was dominant in brackish water stations (the highest abundance at $13.4^{\circ}C$ and 14.1 psu). In freshwater stations of the upstream, two cladoceran species of Polyphemus pediculus and Moina weismani occurred in high abundance in August. Dominant taxa of copepod were clustered to two or three groups mainly due to the difference of salinity gradients. Spatial distribution of mesozooplankton revealed to be determined by salinity gradients which were affected by opening and closing of the artificial dam in Watan stream.

• Journal of Bio-Environment Control
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• v.20 no.3
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• pp.176-181
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• 2011

The fan and pad evaporative cooling system is one of the main cooling methods in greenhouses. Its efficiency is very high, but it has some disadvantages as temperature gradient in greenhouse is large. This study was conducted to reduce the internal temperature gradients in the fan and pad cooling greenhouses. Experiments on cooling performance were carried out in a greenhouse equipped with air duct and integrated fan and pad system as an idea of this study. It showed that the cooling efficiency of an integrated fan and pad system was 75.7% in the first stage and 88.6% in the second stage. When this cooling system was operated for an unshaded and a shaded greenhouse, there were cooling effects of $5.7\sim7.6^{\circ}C$ and $7.4\sim9.7^{\circ}C$ to the control greenhouse, respectively. Maximum temperature differences in a cooling greenhouse, with a length of 18m, were $1.6\sim1.7^{\circ}C$ for shaded conditions and $2.3\sim2.7^{\circ}C$ for unshaded conditions. This greenhouse cooling method, with air duct and integrated fan and pad system, can reduce about 40~50% of the internal temperature gradients in the usual fan and pad cooling greenhouses.

• Journal of Korean Society on Water Environment
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• v.28 no.4
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• pp.561-573
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• 2012

The object of this study was to analyze long-term water quality gradients during 1992-2008 at six sites of Geumho River and near-by two sites of Nakdong River and their influences on fish trophic guilds and tolerance guilds along with ecological health. Water quality including biological oxygen demand (BOD), chemical oxygen demand (COD), conductivity, total phosphorus (TP), total nitrogen (TN), and total suspended solids (TSS) varied largely depending on the sampling locations and seasons. Values of ambient BOD, COD, TP, and TN were greater in the downstream than in the upstream reach, and seasonal and interannual variabilities were also higher in the downstreams. This phenomenon was evident due to a dilution by the Asian monsoon rainfall during the monsoon. These outcomes indicate that point sources near the downstream are important for the chemical conditions, but also seasonal stream runoff was considered as an important factor regulating the chemical conditions. Conductivity decreased rapidly during the summer due to ionic dilution, and nutrients (N, P), BOD, COD had an inverse function of seasonal precipitation. Based on the water quality, we selected two sites (control site = $C_s$ vs. impacted site = $I_s$) for impact analysis of water chemistry on fish community and trophic/tolerant guilds. Fish guild analysis showed that species diversity was higher in the headwater stream ($C_s$) than the impacted downstream ($I_s$), and that the proportion of tolerant and omnivore species were greater in the impacted site of downstream. Comparisons of water quality between Geumho River and Nakdong River indicated that Geumho River was considered as a point source which degradated water quality to the Nakdong River. Overall, chemical water quality and fish guild analysis suggest that even if current chemical quality got better after 1996 due to continuous constructions of wastewater disposal plants near the downstreams, fish compositions of tolerant and omnivores were still dominated the community. Thus, biological restoration based on ecological health is required for the ecosystem conservation.

• Journal of the Korean Society of Marine Environment & Safety
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• v.16 no.4
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• pp.369-379
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• 2010

Zooplankton community structure and copepod production in Seomjin River estuary were investigated at 10 stations along the salinity gradients from May 2009 to February 2010. Total zooplankton taxa were identified to be 31 in the study area and seasonal average abundance of zooplankton was $4,151\;ind.{\cdot}m^{-3}$ during the study period. Zooplankton community was mainly composed of coastal species in dry season. However, brackish species dominated in upper or middle part of this estuary in flood season. This study showed that the growth rates of Acartia spp. and Paracalanus parvus s.l. measured from field experiments were regulated by the variations of Hater temperature and salinity; The annual copepod production estimated by dominant copepod species was $3.49\;g\;C{\cdot}m^{-2}yr^{-1}$, and the relatively high production value could be explained by the high phytoplankton standing stocks and the mass occurrence of coastal and brackish species with relation to various salinity gradients in Seomjin River estuary.

• Korean Journal of Agricultural and Forest Meteorology
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• v.20 no.3
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• pp.233-242
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• 2018

This study explored the richness patterns of vascular plant species and evaluated the effects of the climatic and habitat variables on the observed patterns along elevational gradients on the Mt. Baekhwa, South Korea. Plant data were recorded from 70 plots and a total of 187 plant species with 78 woody and 109 herbaceous species were recorded along two study transects, the Banyasa and Bohyunsa transects, on the Mt. Baekhwa. A total of 154 plant species with 66 woody and 88 herbaceous species and 131 plant species with 58 woody and 73 herbaceous species were recorded along the Banyasa and Bohyunsa transects, respectively. We used simple ordinary least squares regression model, multi-model inference and variation partitioning to analyze the relative contribution of climatic and habitat variables on the elevational richness patterns. Species richness pattern for vascular plants along the Banyasa transect monotonically decreased with elevation, whereas plant species richness showed reversed hump-shaped pattern along the Bohyunsa transect. Although the elevational patterns of species richness for vascular plants were different between the both transects, habitat variables are more important predictors than climatic variables for the elevational patterns of plant species richness along our study transects on the Mt. Baekhwa. These results indicate that elevational diversity patterns of vascular plants may be different even between nearby elevational transects in a mountain ecosystem but the diversity patterns may be controlled by same drivers.

• The Journal of Engineering Geology
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• v.25 no.2
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• pp.291-298
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• 2015

For hydrogeological studies, it is of importance to observe hydraulic head in order to interpret groundwater flow, characterize aquifers, and calibrate groundwater flow model. This study analyzed the zonal variation of hydraulic heads at the eight monitoring wells (GM-1~GM-8) installed with multi-packers in a coastal area and verified vertical and lateral trends of the hydraulic gradients. Hydraulic heads were expressed as the depth of water because the monitoring wells have different depths. The hydraulic gradient at the nearest well (GM-5) shows 0.0142 with increasing trend of hydraulic gradient along depth. This fact indicates typical phenomenon of the discharge area. On the other hand, GM-1 and GM-2 wells in coastal area demonstrate constant hydraulic gradient down to the depth of 100 meters while at the zone of deeper than 100 m the hydraulic gradients illustrate 0.0196 and 0.0735, respectively. This indicates that horizontal flow is dominant at shallower zone than 100 m whereas upward flow is dominant at the zone deeper than 100 m. GM-3 well located farther than the other wells from the coast shows a small hydraulic gradient of 0.0046 that evidences a prevalent horizontal flow between the recharge area and the discharge area.

• Journal of Astronomy and Space Sciences
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• v.22 no.2
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• pp.125-138
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• 2005

S152 is a small bright emission nebula located in the Perseus arm. Its optical diameter corresponds to 1.5 pc for an adopted distance 3.5 kpc. However, S152 is a part of a giant molecular cloud complex, which consists of several dense cores, containing active star-forming sites, and well aligned arm-like features. We analyzed the FCRAO $^{12}CO(J=\;1{\to}0)$ Outer Galaxy Survey data in this region to study the kinematical structure of this region, which resembles a big "scorpion". We found that there exist three different velocity components, about -54.5, -50.4, -48.8 km $s^{-1}$, depending on the position of the "scorpion". There also exist velocity gradients of 0.21 km $s^{-1}pc^{-1}$ and 0.16 km $s^{-1}pc^{-1}$ through the whole extent of the "scorpion". Interestingly, these two velocity gradients show an opposite direction with each other. It is likely that the velocity structure of this region may result from the mergence of different gas clouds, and the interaction with the SNR 109.1-1.0 occurred later, mostly at the region around the "head of the scorpion" only.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.1
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• pp.86-96
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• 2002

The distributions of suspended particulate matter (SPM), chlorophyll a, particulate organic carbon (POC) and nitrogen (PON) and particulate biogenic silica (PBSi) along the salinity gradient were investigated in the Seomjin River estuary from March 1999 to April 2001. Sampling sites were set based on the surface salinity during each cruise rather than geographic locations. Concentrations of SPM were less than 20 mg/L, suggesting relatively low input of terrestrial SPM despite large freshwater discharge through Seomiin River, Chlorophyll a peaks occurred at 5$\~$ 15 psu salinity zone (10$\~$20 km from Nan Cho Island) in November 1999, at 15$\~$25 psu (10$\~$20 km) salinity zone in April 2000 and at 1$\~$15 psu salinity zone (15$\~$20 km) in October 2000 (ca. 8$\~$58%\mu$g/L). Concentrations of POC, PON and PBSi were also high at the same zone. Relatively low ratios of POC to chlorophyll a in mid-salinity zone where POM peak occurred suggests high contribution of living phytoplankton to the total POC. On the other hand, relatively high ratios of POC to chlorophyll $\alpha$ in very low salinity zone and the mouth of estuary indicated relatively high portions of detrital POC. Consequently, the low concentrations of SPM in this estuary and the high concentrations of chlorophyll $\alpha$ and the low ratios of POC to chlorophyll $\alpha$ in the mid-salinity zone suggest that production of living phytoplankton is primary factor in controlling distribution of POM along the salinity gradients in the Seomjin River estuary.

• Proceedings of the KSRS Conference
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• v.1
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• pp.34-37
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• 2006

When tsunami waves propagate across open ocean they are steered by Coriolis force and refraction due to gentle gradients in the bathymetry on scales longer than the wavelength. When the wave encounters steep gradients at the edges of continental shelves and at the coast, the wave becomes non-linear and conservation of momentum produces squirts of surface current at the head of submerged canyons and in coastal bays. HF coastal ocean radar is well-conditioned to observe the current bursts at the edge of the continental shelf and give a warning of 40 minutes to 2 hours when the shelf is 50-200km wide. The period of tsunami waves is invariant over changes in bathymetry and is in the range 2-30 minutes. Wavelengths for tsunamis (in 500-3000 m depth) are in the range 8.5 to over 200 km and on a shelf where the depth is about 50 m (as in the Great Barrier Reef) the wavelengths are in the range 2.5 - 30 km. It is shown that the phased array HF ocean surface radar being deployed in the Great Barrier Reef (GBR) and operating in a routine way for mapping surface currents, can resolve surface current squirts from tsunamis in the wave period range 20-30 minutes and in the wavelength range greater than about 6 km. There is a trade-off between resolution of surface current speed and time resolution. If the radar is actively managed with automatic intervention during a tsunami alert period (triggered from the global seismic network) then it is estimated that the time resolution of the GBR radar may be reduced to about 2 minutes, which corresponds to a capability to detect tsunamis at the shelf edge in the period range 5-30 minutes. It is estimated that the lower limit of squirt velocity detection at the shelf edge would correspond to a tsunami with water elevation of less than 5 cm in the open ocean. This means that the GBR HF radar is well-conditioned for use as a monitor of small and medium scale tsunamis, and has the potential to contribute to the understanding of tsunami genesis research.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.4
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• pp.1151-1159
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• 2014

In this study, two global simple indices are used to investigate climate variability and change in observations. Land-Ocean Contrast (LOC) is an index of area-averaged surface temperature contrast between land and ocean. Meridional Temperature Gradient (MTG) is defined as the mean meridional temperature gradient in the Northern Hemisphere from mid to high latitude and sub-tropical zonal bands. These indices have direct or indirect effects on changing in atmospheric circulations and atmospheric moisture transport from north-south or east-west into East Asia (EA). In addition, warm season hydrometeorology in EA is highly associated with water supplies for coupled human and natural systems including drinking water, irrigation, hydropower generation as well as fisheries. Therefore, in this study, we developed an empirical separation approach for summer rainfall from typhoon and monsoon. An exploratory analysis was also conducted to identify the regional patterns of summer monsoon precipitation over the Korean peninsula within the context of changes in different types of temperature gradients. The results show significant and consistent changes in summer monsoon rainfall during the summer season (June-September) in South Korea.