• Ocean and Polar Research
• /
• 제33권1호
• /
• pp.55-68
• /
• 2011

The distribution and inter-annual variation of nutrients (N, P, Si) and dissolved/particulate organic carbon were investigated in the equatorial thermocline ridge ($7^{\circ}{\sim}11.5^{\circ}N$, $131.5^{\circ}W$) of the northeast Pacific. From the Oceanic Nino Index and Multivariate ENSO Index provided by NOAA, normal condition was observed in July 2003 and August 2005 on the aspect of global climate/ocean change. However, La Ni$\~{n}$a and El Ni$\~{n}$o episodes occurred in July 2007 and August 2009, respectively. Thermocline ridge in the study area was located at $9^{\circ}N$ in July 2003, $8^{\circ}N$ in August 2005, $10^{\circ}N$ in July 2007, and $10.5^{\circ}N$ in August 2009 under the influence of global climate/ocean change and surface current system (North Equatorial Counter Current and North Equatorial Current) of the northeast Pacific. Maximum depth integrated values (DIV) of nutrients in the upper layer (0~100 m depth range) were shown in July 2007 (mean 21.12 gN/$m^2$, 4.27 gP/$m^2$, 33.72 gSi/$m^2$) and higher variability of DIV in the equatorial thermocline ridge was observed at $10^{\circ}N$ during the study periods. Also, maximum concentration of dissolved organic carbon (DOC) in the upper 50 m depth layer was observed in July 2007 (mean $107.48{\pm}14.58\;{\mu}M$), and particulate organic carbon (POC, mean $9.42{\pm}3.02\;{\mu}M$) was similar to that of DOC. Nutrient concentration in the surface layer increased with effect of upwelling phenomenon in the equatorial thermocline ridge and La Ni$\~{n}$a episode, which had formed in the central Pacific. This process also resulted in the increasing of organic carbon concentration (DOC and POC) in the surface layer. From these results, it is suggested that spatial and temporal variation of chemical and biological factors were generated by physical processes in the equatorial thermocline ridge.

• 한국산림과학회지
• /
• 제84권3호
• /
• pp.369-376
• /
• 1995

흑백 항공사진을 이용하여 산지급류하천(山地急流河川)의 하상변동(河床變動)을 파악한 결과, 다음과 같은 면에서 항공사진이 유효정보로 사용될 수 있다. 1. 항공사진 및 현지조사에 의한 하도폭(河道幅) 측정값의 직선회귀식은 Y=1.0+0.94X($r^2=0.98$)로, 두 인자간의 높은 상관관계가 확인되어 항공사진이 하도폭 해석에 유효하게 사용될 수 있다. 2. 항공사진 판독에 의해 하도내의 하상퇴적지(河床堆積地)와 유로(流路)의 평면적(平面的) 구분(區分)이 가능하였으며, 또한 하상퇴적지(河床堆積地)의 평면적(平面的) 분포(分布) 상황(狀況)과 유로(流路)의 규모(規模) 및 형성과정(形成過程)을 추정 할 수 있다. 3. 촬영시기가 상이한 항공사진을 판독하므로서 각 시기별 유로특성(流路特性)을 파악할 수 있었으며, 또한 이를 비교, 분석하므로서 하상변동(河床變動)에 강하게 영향하는 유로변동(流路變動) 과정(過程)을 추정할 수 있다. 4. 항공사진상의 하도폭(河道幅) 측정(測定), 하상(河床)의 평면형태(平面形狀) 해석(解析) 및 유로변동(流路變動) 파악(把握) 등에 의해 하상미지형도(河床微地形圖)를 작성할 수 있으며, 이를 기초로 하상퇴적지(河床堆積地)의 평면적(平面的) 해석(解析)이 가능하다.

• 대한원격탐사학회지
• /
• 제13권1호
• /
• pp.1-12
• /
• 1997

지구상에서 가장 따뜻한 해수면 온도를 가지고 있는 열대 서태평양은 많은 대류 시스템 과 큰 연강수략에 의해 특징지워진다. GMS-IR 자료로부터 얻어진 운량자료를 이용하여 이 지역 에서의 운량 일변동을 조사하였다. 구름의 시공간적인 분포에 관한 특징은 주로 운량의 일주기 및 반일주기 성분의 진폭과 주기를 통해 조사되었다. 대기-해양의 상호작용에 의해 운량 변동에는 다양한 주기들이 나타났는데, 특히 30-60일, 17-20 일, 7-8일, 일주기와 반일주긱가 탁월하였다. 북반구 겨울(남반구 여름) 기간 동안 뉴기니아, 호주 북부에 인접한 해양 그리고 160도E 동쪽에서 큰 운량이 분포하는 것으로 조사되었다. 육지와 인 접 해성에서의 운량 일변동은 외양의 경우에 비해 약 2배 정도 크게 나타났는데, 이것은 주로 해 양과 육지의 전형적인 비열차에 기인한 것으로 여겨진다. 운량의 최대치와 최소치는 육상의 경우 18:00시와 09:00시에 나타났고, 외양에서는 정오와 21:00시에 나타났다. 1일주기 성분의 진폭은 반 일주기 성분에 비해 육상에서 4.7배, 외양에서 1.5배 정도 크게 나타났다.

• 생태와환경
• /
• 제41권4호
• /
• pp.512-518
• /
• 2008

This study were to evaluate trophic conditions, N : P ratios, and empirical relations of chlorophyll (CHL) systematically using TN, TP, and CHL values in agricultural reservoirs and drinking water supplying dams. During the study, nutrients and CHL varied depending on seasonal conditions and types of the reservoirs, but most reservoirs were diagnozed as eutrophic to hypertrophic. Mass ratios of TN : TP averaged 93.1 (range: $0.68{\sim}1342$) and about 96.6 % of the total observations (n=516) was > 17 in the N : P ratios. This result suggests that P was a potential factor limiting algal growth in the entire reservoir. Thus, TN : TP ratios were a function of phosphorus rather than nitrogen. Regression analysis of log-transformed N : P ratios against TP in DWDRs and ARs showed that ratios were linearly declined with an increase of TP ($R^2$>0.66; p<0.001). Seasonal mean CHL was minimum ($4.3{\mu}g\;L^{-1}$, range: $0.1{\sim}39.7{\mu}g\;L^{-1}$) in premonsoon, and was similar between the monsoon and postmonsoon. In contrast, one of the tremendous features was that values of CHL was greater in the ARs than DWDRs. Thus, the spatial and temporal patterns in CHL were similar to those of TP but not TN. Empirical models of CHL-TP showed that CHL variation could explain average 15.3% and 11.3% in DWDRs and ARs, respectively. Seasonal analysis of empirical models showed that CHL-TP relations were stronger in postmonsoon than those of premonsoon and monsoon.

• 한국대기환경학회지
• /
• 제31권3호
• /
• pp.201-208
• /
• 2015

We investigated the pollution levels of $PM_{2.5}$ at Wangsimni station at which four subway lines (Line 2, Line 5, the Jungang line, and the Bundang Line) are simultaneously under the operation. The analysis of $PM_{2.5}$ was made for the period of 1~ 11 Nov. 2014. The results of our field campaign were analyzed to assess the effects of various factors and conditions on the $PM_{2.5}$ pollution (such as installation of the screen door, density of floating population, weekdays and weekend, and the depth of platforms). The mean concentrations of $PM_{2.5}$ in each subway line of the Wangsimni station was measured as: the line 2 ($22.5{\mu}g/m^3$) ; the line 5 ($18.3{\mu}g/m^3$) ; the Jungang line ($31.8{\mu}g/m^3$); and the Bundang line ($32.2{\mu}g/m^3$). Based on the detailed analysis of $PM_{2.5}$ pollution at four subway lines, we aimed to provide some perspectives on reducing the concentration of ultrafine particles in a highly populated urban area.

• Ocean and Polar Research
• /
• 제39권3호
• /
• pp.169-179
• /
• 2017

The "GeoDrifter" is a newly-developed surface drifter with high temporal resolution. It is the first time that high-frequency drifters have been deployed in the East/Japan Sea. The purpose of this study is to introduce the phenomena experienced by these drifters flowing along with the Tsushima Current across the East/Japan Sea, focusing on high-frequency variability, and to discuss them in comparison with previous observations. The observed basin-scale circulation of the Tsushima Current generally coincides well with the known schematic circulation. The GeoDrifter trajectories also show inertial oscillations almost everywhere in the oceanic regions of the East/Japan Sea, strong semi-diurnal tidal currents in the western part of Korea Strait, diurnal currents much stronger than semi-diurnal currents in the upstream region of the Nearshore Branch off the Japanese coast, and many warm eddies in the Yamato Basin, all comparable to the observational results reported in the previous studies. An interesting point is that the semi-diurnal tidal currents undergo a great spatial variation in the western part of the Korea Strait. The observed features that cannot be explained are, among others, strong counter-clockwise motions with oscillating period about 51 hours appearing in the upstream region of the Nearshore Branch off the Japanese coast and the different tidal behaviors between upstream and downstream regions of the latter.

• 한국환경과학회지
• /
• 제24권2호
• /
• pp.163-174
• /
• 2015

The Youngsan Lake was constructed to supply agricultural water to the extensive rice fields in the basin of the lake in 1981. Hypoxia has often developed in the bottom water of the lake during the warm season although the water depth is relatively shallow (< 16 m). We investigated the spatial and temporal variations of dissolved oxygen (DO) and physical properties such as water temperature, salinity and turbidity to elucidate the effects of change in physical properties on DO dynamics in the lake. Vertical profiles of DO, temperature, salinity, and water density were also explored to verify the development of stratification in relation to DO variation in the water column. Hypoxia (DO < $2mg\;L^{-1}$) was not observed in the upper regions whereas hypoxia was detected in the lower regions during the warm season. Thermocline generally developed in the lower regions during the warm season unlike the previous studies in which no thermocline was observed. However, water column was well mixed when freshwater water was discharged from the reservoir through the sluice gate of the dike. DO concentrations also decreased when halocline or pycnocline developed during the dry season suggesting that the vertical stratification of water column affects DO dynamics although the water depth is shallow in the Youngsan lake.

• Asian Journal of Atmospheric Environment
• /
• 제10권2호
• /
• pp.57-66
• /
• 2016

Wet deposition fluxes of ions at a coastal site in southwestern Japan in the period 1996-2003 were investigated to quantify the respective contributions of cyclone-, stationary front- and typhoon-associated rains. On average, the deposition fluxes of terrigenous-origin ions, nss-$SO_4{^{2-}}$, $NO_3{^-}$, $NH_4{^+}$ and nss-$Ca^{2+}$ were $37.6{\pm}7.3$, $16.3{\pm}4.2$, $19.0{\pm}3.4$ and $9.6{\pm}4.8meq\;m^{-2}yr^{-1}$, and those of $Na^+$ and $Cl^-$, the major ions in sea water, were $97.0{\pm}38.2$ and $115.2{\pm}48.2meq\;m^{-2}yr^{-1}$, respectively. Cyclone-associated rain constituted more than 50% of the fluxes of the terrigenous ions in almost all years. Stationary front-associated rain also contributed significantly, although the contribution was lower than the contribution by Cyclone-associated rain in almost all years. In particular, the wet deposition flux of nitrogen compounds of $NO_3{^-}$ and $NH_4{^+}$, which are important nutrients for micro-bioactivities in sea surface water, was dominated by cyclone-associated rain. Due to the extreme abundance of $Na^+$ and $Cl^-$ in the rainwater of typhoons, the fluxes of $Na^+$ and $Cl^-$ were contributed substantially by typhoons in years with typhoons' passage although cyclones were still the largest contributor to the fluxes. These results indicate the dominance of cyclones in the wet deposition to the East China Sea areas and the necessity to take rain types into account for a more accurate elucidation of the temporal and spatial variation of the wet deposition.

• 한국물환경학회지
• /
• 제26권6호
• /
• pp.943-947
• /
• 2010

Runoff ratio of paddy fields for the application of Event Mean Concentration (EMC) method was studied. To measure actual runoff ratio of paddy fields, a field monitoring was conducted for 2008 ~ 2009 period. Long-term rainfall data of four cities in major river basins were analyzed and weighting factors were developed to consider temporal and spatial variation of rainfall distribution of Korean peninsula. The observed runoff ratio ranged 0.00 ~ 1.20 and arithmetic mean were 0.25, respectively. However, the representative runoff ratio for paddy fields was determined as 0.41 according to the method suggested by National Institute of Environmental Research (NIER).

• 한국환경과학회지
• /
• 제22권1호
• /
• pp.119-129
• /
• 2013

We compared equilibrium evaporation($E_{equili}$) eddy-covariance($E_{eddy}$) with soil moisture data($E_{SMseries}$) which were measured with a 2 hours sampling interval at three points for a humid forest hillslope from May 5th to May 31th in 2009. Accumulations of $E_{eddy}$, $E_{equili}$ for the study period were estimated as 2.52, 3.28 mm and those of $E_{SMseries}$ were ranged from 1.91 to 2.88 mm. It suggested that the eddy-covariance method considering the spatial heterogeneity of soil evaporation is useful to evaluate the soil evaporation. Method A, B and C were proposed using mean meterological data and daily moisture variation and the computations were compared to eddy-covariance method and equilibrium evaporation. The methods using soil moisture data can describe the variations of soil evaporation from eddy-covariance through simple moving average analysis. Method B showed a good matched with eddy-covariance method. This indicated that Dry Surface Layer (DSL) at 14:00 which was used for method B is important variable for the evaluation of soil evaporation. The total equilibrium evaporation was not significantly different to those of the others. However, equilibrium evaporation showed a problem in estimating soil evaporation because the temporal tendency of $E_{equili}$ was not related with the those of the other methods. The improved understanding of the soil evaporation presented in this study will contribute to the understandings of water cycles in a forest hillslope.