• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.15 no.2
• /
• pp.51-61
• /
• 2010

Surface particulate organic carbon (POC) concentration was measured in the Northeastern Gulf of Mexico on 9 cruises from November 1997 to August 2000 to investigate the seasonal and spatial variability related to synchronous remote sensing data (Sea-viewing Wide Field-of-view Sensor (SeaWiFS), sea surface temperature (SST), sea surface height anomaly (SSHA), and sea surface wind (SSW)) and recorded river discharge data. Surface POC concentrations have higher values (>100 $mg/m^3$) on the inner shelf and near the Mississippi Delta, and decrease across the shelf and slope. The inter-annual variations of surface POC concentrations are relatively higher during 1997 and 1998 (El Nino) than during 1999 and 2000 (La Nina) in the study area. This phenomenon is directly related to the output of Mississippi River and other major rivers, which associated with global climate change such as ENSO events. Although highest river runoff into the northern Gulf of Mexico Coast occurs in early spring and lowest flow in late summer and fall, wide-range POC plumes are observed during the summer cruises and lower concentrations and narrow dispersion of POC during the spring and fall cruises. During the summer seasons, the river discharge remarkably decreases compared to the spring, but increasing temperature causes strong stratification of the water column and increasing buoyancy in near-surface waters. Low-density plumes containing higher POC concentrations extend out over the shelf and slope with spatial patterns and controlled by the Loop Current and eddies, which dominate offshore circulation. Although river discharge is normal or abnormal during the spring and fall seasons, increasing wind stress and decreasing temperature cause vertical mixing, with higher surface POC concentrations confined to the inner shelf.

• Journal of the Korean earth science society
• /
• v.38 no.1
• /
• pp.35-48
• /
• 2017

This study analyzed the obvious increasing tendency of summer (June to August) rainfall in the region of Korea- and northern China ($35^{\circ}-40^{\circ}N$, $110^{\circ}-130^{\circ}E$) in the late 1990s. In order to investigate the causes of the increase in summer rainfall since 1998, we analyzed the difference of the rainfall average between 1998-2012 and 1981-1997. The analysis of the 850 hPa stream flows showed that the huge anomalous anticyclonic circulations were developed in North Pacific and eastern Australia. In both hemispheres, the anomalous easterlies (anomalous trade winds) were strengthened from the equatorial central Pacific to the tropical western Pacific by the anomalous circulations, which was an anomalous circulation pattern shown in La $Ni{\tilde{n}}a$ years. As for the 200 hPa stream flows, the huge anomalous cyclonic circulations were also developed in both South Pacific and North Pacific. These two anomalous circulations reinforced the anomalous westerlies in the equatorial central and western Pacific, leading to the increase in summer rainfall in the region of Korea- and northern China since the late 1990s in association with La $Ni{\tilde{n}}a$ pattern, which was resulted in strengthening the Walker circulation. Recently in East Asia, the local Hadley circulation has been strengthened in which upward flows in the equatorial western Pacific and mid-latitude region of East Asia have descended in the subtropical western Pacific.

• Atmosphere
• /
• v.28 no.3
• /
• pp.325-336
• /
• 2018

This study investigates robust features of interdecadal changes in the Northern hemisphere summer tropical-extratropical teleconnection occurred around the mid-to-late 1990s by analyzing four different reanalysis data for atmospheric circulation and temperature, two precipitation reconstructions, and two sea surface temperature (SST) data during the satellite observation era of 1980~2017. For the last 38 years, there has been a significant increasing trend in anticyclonic circulation at lower and upper troposphere and 2 m air temperature with wavenumber-5 Rossby wave structure in the Northern Hemisphere (NH) extratropics. The increase has been accompanied with the significant weakening and northward shift of jet stream over Eurasia and the North Pacific. It is further found that there has been a significant interdecadal shift occurred around the mid-to-late 1990s in the two distinct modes of tropical-extratropical teleconnection: Western Pacific-North America (WPNA) and circumglobal teleconnection (CGT) pattern. After mid-to-late 1990s, the WPNA has played more important role in modulating the extratropical atmospheric circulation and surface climate, which has been preferentially occurred during the El $Ni{\tilde{n}}o$-Southern Oscillation (ENSO) decaying or transition summer such as 1998, 2010 and 2016. During these summers, severe heat waves were occurred over many parts of the NH extratropics due to the combined effect of the increasing trend in the barotropic anticyclonic circulation and the significant WPNA across the NH. Although weakened, the CGT also contributed to some of hot summers over many parts of the NH extratropics such as 1999, 2000, 2008, 2011, and 2012 when weak to moderate La $Ni{\tilde{n}}o$ was persisted.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2011.11a
• /
• pp.150-151
• /
• 2011

최근 25년간(1986-2010년)의 우리나라 기상청 및 일본 기상청 자료를 사용하여 엘니뇨 라니냐 현상과 태풍과의 관계를 분석하였다. 특히, 이번 연구에서는 태풍의 세기에 주목하여 분석하였다. 주요 연구 결과는 다음과 같다. 태풍의 세기를 나타내는 평균 중심최저기압과 평균 최대풍속은 엘니뇨 발생년에 959.3hPa과 35.8m/s, 라니냐 발생년에 965.5hPa과 33.7m/s 그리고 25년 전 기간에 대하여는 962.3hPa과 35.0m/s이었다. 즉, 엘니뇨 발생년의 태풍의 세기가 라니냐 발생년의 태풍의 세기보다 강함을 알 수 있다. 구체적으로 평균 중심최저기압은 약 6hPa 낮고, 평균 최대풍속은 2.1m/s 강하다. 이와 같은 결과는 태풍의 발생 해역과 밀접히 관련되어 있다. 즉, 엘니뇨 발생년에 태풍은 동경 150도 이동 해역과 북위 10도 이남 해역에서 상대적으로 더 많이 발생하고, 라니냐 발생년의 태풍은 동경 150도 이서 해역과 북위 20도 이북 해역에서 더 많이 발생한다. 동경 150도 이동 해역과 북위 10도 이남 해역에서 발생한 태풍은 북태평양의 광범위한 고수온역을 보다 장시간 이동하게 되므로 더 강하게 발달할 수 있다.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.26 no.1
• /
• pp.75-83
• /
• 2020

This study investigated the effects of El Niño and La Niña on coastal upwelling in the East Sea of Korea using long-term (1967-2017) water temperature observation data and Oceanic Niño Index (ONI). As a result of time series analysis of water temperature, the occurrence frequency of summer coastal upwelling was the highest in the southeastern (Ulgi ~ Gimpo) coast. In 1987-1988 and 1997-1998, when the annual fluctuations of ONI plunged more than 2.5, the water temperature in whole coast areas of the East Sea (Busan ~ Goseung) rose by 4 ~ 7 ℃. The temperature structure of the East Sea coastal water was different when El Niño was strong with ONI above 1.5 and La Niña with strong ONI below -0.8. When El Niño is strong, the water temperature anomaly in coastal waters is negative. This is due to the strong baroclinic tilting and the formation of shallow temperature stratification in the coastal waters. The strong La Niña season is opposite to the strong El Niño season, whereas the water temperature anomaly is positive. In addition, the baroclinic tilting is weaker than the time of strong El Niño and the temperature stratification is formed deeper than the time of strong El Niño. The formation of temperature stratification at shallow depths when El Niño is strong can increase the probability of occurrence coastal upwelling caused by southerly winds in the summer season. On the contrary, when La Niña is strong, occurrence of coastal upwelling is less likely even if the southerly wind blows continuously. This is because the temperature stratification is formed at deeper than when El Niño is strong.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.13 no.3
• /
• pp.200-209
• /
• 2008

Particle fluxes were measured with a time-series sediment trap from July 2003 to June 2005 at the St. KOMO(KOMO; Korea Deep-Sea Environmental Study Long-Term Monitoring Station, $10^{\circ}30'N,\;131^{\circ}20'W$) in the northeastern Pacific. Total mass fluxes at a depth of 4,960 m showed distinct seasonal variations with high values in the winter(December-February) and spring(March-May) and low values in the summer(June-August) and fall(September-November). Biogenic origin fluxes also displayed distinct seasonal variations similar to total mass fluxes. Particularly, calcium carbonate fluxes in winter and spring were more than two times greater than those in summer and fall. The prominent seasonal variations of total mass and biogenic fluxes were closely related with the seasonal changes of primary production in the surface waters; in winter and spring, primary production increased due to the enhanced supply of nutrients below the surface mixed layer by strong wind and less stratification, whereas it decreased as a result of the less supply of nutrient by reduced wind speed and strong stratification in summer and fall. The seasonal variations of total mass and biogenic fluxes in this study were higher than the differences of total mass and biogenic fluxes caused by the environmental changes such as El $Ni\tilde{n}o$ and La $Ni\tilde{n}a$ events in the previous studies. In order to understand the effects of El $Ni\tilde{n}o$ and La $Ni\tilde{n}a$ on the particle flux, therefore, the seasonal variation of particle flux in the northeastern equatorial Pacific needs to be well defined.

• Journal of the Korean earth science society
• /
• v.22 no.5
• /
• pp.415-422
• /
• 2001

Studies of atmospheric general circulation in the troposphere and stratosphere are very important to understand the influence of human activities on the global climate and its change. Recently, the existence of an annual cycle in the circulation has been reported by a number of studies. In this study, the residual mean meridional circulation is calculated by the TEM momentum and continuity equations for the period from December 1985 to November 1995 (10 years), and the long-term variations of the circulation and mass fluxes across the 100hPa surface are examined. The multiple regression statistical model is used to obtain quantitatively the long-term variations. This study is focused especially on mean meridional circulation in the troposphere and stratosphere associated with ENSO (El Ni${\tilde{n}}$o-Southern Oscillation) which is known as a cause of the unusual weather, global climate, and its change. The results show that the global scale troposphere-stratosphere mean meridional circulation is intensified during El Ni${\tilde{n}}$o event and QBO (quasi-biennal oscillation) easterly phase and weakened during La Ni${\tilde{n}}$o event and QBO westerly phase. The signal of Mount Pinatubo volcanic eruption in June 1991 is obtained. Due to the volcanic eruption the global scale troposphere-stratosphere mean meridional circulation is abruptly intensified.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2011.06a
• /
• pp.232-233
• /
• 2011

이 연구에서는 최근 25년간(1986-2010년)의 우리나라 기상청 및 일본 기상청 자료를 사용하여 엘니뇨 라니냐 현상과 태풍과의 관계를 분석하였다. 여기서는 엘니뇨감시해역의 해면수온의 기준치와의 차의 5개월 이동평균치가 6개월 이상 계속하여 $+0.5^{\circ}C$ 이상 이 된 경우를 엘니뇨현상, $-0.5^{\circ}C$ 이하가 된 경우를 라니냐현상이라고 정의한다. 그리고 엘니뇨 발생년은 엘니뇨현상이 시작된 해부터 종료된 해까지를, 라니냐 발생년은 라니냐현상이 시작된 해부터 종료된 해까지로 정의한다. 주요 분석 결과는 다음과 같다. 전 기간에 대한 태풍의 연평균 발생 수는 25.4개이다. 이는 60년간(1951-2010년)의 연평균 태풍 발생 수 26.3개보다 약 1개 적은 결과로 최근 지구온난화와 관련하여 태풍의 발생 수가 감소 추세를 보이고 있다는 연구 결과를 뒷받침한다. 엘니뇨 발생년의 연평균 태풍 발생 수는 23.9개이고, 라니냐 발생년의 그것은 24.9개이다. 적도 부근 서부 태평양의 따뜻한 물이 동쪽으로 이동하여 동부 태평양의 해면수온이 평년 이상으로 높아지는 엘니뇨 발생년에 태풍의 발생 수가 감소한다는 사실을 알 수 있다. 태풍의 세기를 나타내는 평균 중심최저기압과 평균 최대풍속은 엘니뇨 발생년에 959.3hPa과 35.8m/s, 라니냐 발생년에 965.5hPa과 33.7m/s 그리고 25년 전 기간에 대하여는 962.3hPa과 35.0m/s이었다. 엘니뇨 발생년의 태풍의 세기가 라니냐 발생년의 태풍의 세기보다 강함을 알 수 있다.

• Journal of the Korean earth science society
• /
• v.21 no.5
• /
• pp.503-524
• /
• 2000

Intercomparisons between four kinds of data have been done to estimate the accuracy of satellite observations and model reanalysis for middle and lower tropospheric thermal state over regional oceans. The data include the Microwave Sounding Units (MSU) Channel 2 (Ch2) brightness temperatures of NOAA satellites and the vertically weighted corresponding temperature of ECMWF GCM (1980-93). The satellite data for midtropospheric temperatures are MSU2 (1980-98) in nadir direction and SC2 (1980-97) in multiple scans, and for lower tropospheric temperature SC2R (1980-97). MSU2 was derived in this study while SC2 and SC2R were described in Spencer and Christy (1992a, 1992b). Temporal correlations between the above data were high (r${\ge}$0.90) in the middle and high latitudes, but low(r${\sim}$0.65) over the low latitude and more convective regions. Their values with SC2R which included the noises due to hydrometeors and surface emission were conspicuously low. The reanalysis shows higher correlation with SC2 than with MSU2 partially because of the hydrometeors screening. SC2R in monthly climatological anomalies was more sensitive to surface thermal condition in northern hemisphere than MSU2 or SC2. The first EOF mode for the monthly mean data of MSU and ECMWF shows annual cycle over most regions except the tropics. The mode in MSU2 over the Pacific suggests the east-west dipole due to the Walker circulation, but this tendency is not clear in other data. In the first and second modes for the Ch2 anomalies over most regions, the MSU and ECMWF data commonly indicate interannual variability due to El Ni${\tilde{n}$o and La Ni${\tilde{n}$a. The substantial disagreement between observations and model reanalysis occurs over the equatorial upwelling region of the western Pacific, suggesting uncertainties in the model parameterization of atmosphere-ocean interaction.

• Proceedings of the Korean Quaternary Association Conference
• /
• 2004.11a
• /
• pp.37-43
• /
• 2004

The response of the CCCma coupled climate model to the imposition of LGM conditions is investigated. The global mean SAT and SST decrease by about $10^{\circ}C$ and $5.6^{\circ}C$ in the coupled model. Tropical SST decreases by $6.5^{\circ}C$, whereas CLIMAP reconstructions suggest that the tropics cool by only about $1.7^{\circ}C$, although the larger tropical cooling is consistent with the more recent proxy estimates. With the incorporation of a full ocean component, the coupled model gives a realistic spatial SST pattern, capturing features associated with ocean dynamics that are seen in the CLIMAP reconstructions. The larger decrease of the surface temperature in the model is associated with a reduction in global precipitation rate (about 15%). The tropical Pacific warm pool retreats to the west and a mean La $Ni\tilde{n}a$-like response is simulated with less precipitation over the central Pacific and more in the western tropical Pacific. The more arid ocean climate in the LGM results in an increase in SSS almost everywhere. This is particularly the case in the Arctic Ocean where large SSS increase is due to a decrease in river discharge to the Arctic Ocean associated with the accumulation of snow over the ice sheet, but in the North Atlantic by contrast SSS decreases markedly. This remarkable reduction of SSS in the North Atlantic is attributed to an increase in fresh water supply by an increase in discharges from the Mississippi and Amazon rivers and an increase in P-E over the North Atlantic ocean itself. The discharges increase in association with the wetter LGM climate south of the Laurentide ice sheet and in South America. The fresh water capping of the northern North Atlantic results in a marked reduction of deep convection and consequently a marked weakening of the North Atlantic overturning circulation. In the LGM, the maximum overturning stream function associated with the NADW formation decreases by about 60% relative to the control run, while in the Southern Ocean, oceanic convection is stronger in the LGM due to reduced stratification associated with an increase in SSS and a decrease in SST and the overturning stream function associated with the formation of AABW and the outflow increases substantially.