• 대기
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• 제18권4호
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• pp.507-524
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• 2008

In this paper, future climate changes over East Asia($20^{\circ}{\sim}50^{\circ}N$, $100^{\circ}{\sim}150^{\circ}E$) are projected by anthropogenic forcing of greenhouse gases and aerosols using coupled atmosphere-ocean general circulation model (AOGCM) simulations based on Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) B1, A1B and A2 scenarios. Before projection future climate, model performance is assessed by the $20^{th}$ Century (20C3M) experiment with bias, root Mean Square Error (RMSE), ratio of standard deviation, Taylor diagram analysis. The result of examination of the seasonal uncertainty of T2m and PCP shows that cold bias, lowered than that of observation, of T2m and wet bias, larger than that of observation, of PCP are found over East Asia. The largest wet bias is found in winter and the largest cold bias is found in summer. The RMSE of temperature in the annual mean increases and this trend happens in winter, too. That is, higher resolution model shows generally better performances in simulation T2m and PCP. Based on IPCC SRES scenarios, East Asia will experience warmer and wetter climate in the coming $21^{st}$ century. It is predict the T2m increase in East Asia is larger than global mean temperature. As the latitude goes high, the warming over the continents of East Asia showed much more increase than that over the ocean. An enhanced land-sea contrast is proposed as a possible mechanism of the intensified Asian summer monsoon. But, the inter-model variability in PCP changes is large.

• Fisheries and Aquatic Sciences
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• 제26권11호
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• pp.639-648
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• 2023

The sea surface temperature (SST) and ocean heat content in the Korea Waters are gradually increased. Especially the increasing trend of annual mean SST in the Korea Water is higher about 2.6 times than the global mean during past 55 years (1968-2022). Before 2010s, the increasing trend of SST was led by winter season in the Korea Waters. However, this pattern was clearly changed after 2010s. The increasing trend of SST during summer is higher about 3.9 times than during winter after 2010s. We examine the long-term variations of several ocean and climate factors to understand the reasons for the long-term pattern changes of SST between summer and winter in recent. Tsushima warm current was significantly strengthened in summer compare to winter during past 33 years (1986-2018). The long-term patterns of Siberian High and East Asian Winter Monsoon were definitely changed before and after early- or mid-2000s. The intensities of those two climate factors was changed to the increasing trend or weakened decreasing trend from the distinctive decreasing trend. In addition, the extreme weather condition like the heatwave days and cold spell days in the Korea significantly increased since mid- or late-2000s. From these results, we can consider that the occurrences of frequent and intensified marine heatwaves during summer and marine cold spells during winter in the Korea Waters might be related with the long-term pattern change of SST, which should be caused by the long-term change of climate factors and advection heat, in a few decade.

• 한국지구과학회지
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• 제44권1호
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• pp.1-12
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• 2023

해양의 파랑은 지구온난화 및 기후변화의 중요한 지표 중 하나로 인식되고 있다. 기후변화와 동아시아 몬순의 영향을 직접적으로 받는 황해 및 동중국해역에서의 유의파고 및 파향의 시공간 변동성 연구가 필요하다. 본 연구에서는 유럽중기예보센터(European Centre for Medium-Range Weather Forecasts; ECMWF)에서 제공하고 있는 5세대 모델 재분석장 (ECMWF Reanalysis 5, ERA5) 자료를 활용하여 황해 및 동중국해역에서의 유의파고와 파향의 공간분포와 계절 및 경년변동을 포함하는 시공간 변동성을 분석하였다. 모델 재분석자료를 활용한 유의파고와 파향의 변동성 분석에 앞서 이어도 해양과학기지 관측 자료와의 비교를 통하여 정확도를 검증하였다. 평균 유의파고는 0.3-1.6 m의 범위를 보였으며 북쪽에 비해 남쪽이 높고 연안에 비해 황해 중심부에서 높은 공간분포 특성을 보였다. 유의파고의 표준편차 또한 평균과 유사한 양상을 나타내었다. 황해에서 유의파고와 파향은 뚜렷한 계절변동성을 보였다. 유의파고의 경우 전반적으로 겨울철에 가장 높았으며 늦봄 또는 초여름에 가장 낮았다. 파향은 계절풍의 영향으로 겨울철에는 주로 남쪽으로 전파되었으며 여름철에는 북쪽으로 전파되는 특성이 나타났다. 유의파고의 계절변동은 여름철 태풍 등의 영향으로 해마다 연 진폭의 큰 변화를 가진 강한 경년변동성을 보였다.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2003년도 추계학술발표회
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• pp.163-166
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• 2003

The seasonal mean wind direction and wind speed in a greater coasting area are investigated using the ECMWF(European Centre for Medium-Range Weather Forecasts) data for 11 years from 1985 to 1995. In winter, the main wind direction in Korea and vicinity, Taiwan and vicinity, and the North Pacific Ocean of middle latitudes is a northwesterly wind, northeasterly wind, and westerly wind respectively. The wind speed is strongest in the East China Sea, the South China Sea, and the North Pacific Ocean of low latitudes(Beaufort wind scale 5-6). A distribution pattern of wind direction in spring and fall is similar to that in winter. Seasonal mean wind speed is strongest in winter and the next is fall. The wind speed in summer is generally weak. However, that in the Indochina and vicinity is strong by the influence of Asian monsoon.

• 대기
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• 제11권2호
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• pp.6-12
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• 2001

The East Asian monsoon is generally accompanied with the quasi-stationary front along the northern and northwestern periphery of the subtropical anticyclone in the boundary zone of the polar cold air mass and the tropical warm air mass. The rainy season in Korea has been called as Changma since the middle of 1500s. In meteorology, the rainy season with the quasi-stationary front, the Changma front, during the early summer has been defined as the Changma since 1905. The difference of meaning on Changma between meteorologists and the general public sometime does give a confusion. For example, the heavy rainfall event after the retreat of Changma is recognized as Changma by the general public, but not by most of meteorologists. The decision of the onset and retreat dates of Changma among the meteorologists is also ambiguous because of different viewpoints on the definition of Changma. In this study we survey the etymology and definition of Changma.

• 대기
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• 제27권1호
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• pp.79-91
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• 2017

It is imperative to understand the characteristics of atmospheric circulation patterns under the climate system due to its impact on climatic factors. Thus this study focused on analyzing the impact of the atmospheric circulation on the relationship between precipitation and temperature regionally. Here we used monthly gridded observational data (i.e., CRU-TS3.2, NOAA-20CR V2c) and HadGEM2-AO climate model by RCP8.5, for the period of 1960~1999 and 2060~2099. The experiment results indicated that the negative relationship was presented over East Asia and Europe during summer. On the other hand, at around Korea (i.e. EA1: $31^{\circ}N{\sim}38^{\circ}N$, $126^{\circ}E{\sim}140^{\circ}E$) and Northwestern Europe (i.e. EU1: $48^{\circ}N{\sim}55^{\circ}N$, $0^{\circ}E{\sim}16^{\circ}E$) in winter, strong positive relationship dominate due to warm moist advection come from ocean related to intensity variation of the East Asian winter monsoon (EAWM) and North Atlantic Oscillation (NAO), respectively. It was found that values of positive relation in EA1 and EU1 at the end of the 21st century is regionally greater than at the end of 20th century during winter since magnitude of variation of the EAWM and NAO is projected to be greater in the future as result of simulation with RCP 8.5. Future summer, the negative correlations are weakened in EA1 region while strengthened in EU1 region. For better understanding of correlations with respect to RCP scenarios, a further study is required.

• 생태와환경
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• 제35권3호통권99호
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• pp.160-171
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• 2002

본 연구는 낙동강 하류에서 장마 기간의 강우가 수질 변화에 미치는 영향을 평가하였다. 1997년 하절기 장마기간 주요 집수역의 강우상황을 분석하고 낙동강 하류역 (물금)에서 $1{\sim}3$일 간격으로 수질항목(수소이온농도,　탁도, 투명도, 엽록소-a, 용존산소, 전기전도도, 수온)과　영양염류 등(총질소, 총인, 질산성 질소, 암모니아성 질소, 인산 인, 규산)을 측정하였다. 또한 갈수기 이후 큰 강에서 최초 집중강우가 수질 변화에 미치는 영향을 평가하기 위하여 수질 자동측정장비(Hydrolab $Recorder^{TM}$)를　이용하여 장마 초기강우 전후에 1시간 간격으로 수질　및 수위변화를 모니터링하였다. 우리나라는 연간 강우의약 50%이상이 하절기 ($6{\sim}8$월)에 집중되며,　특히 장마는6월 하순경에 시작하여 7월 중순까지 약 한 달간 하천수환경에 크게 영향을 미친다. 1997년 장마기간동안 낙동강의 주요 집수역에서 50mm 이상의 강우가 내린 횟수는 총 5회였고,　여름기간 중 물금 지역에서 물리${\cdot}$화학적 환경요인에 급격한 변화가 일어난 시기는 장마 초기를 전후해서였다. 초기강우로 기초수질항목 중 수온, 수소이온농도, 전기전도도, 용존산소는 큰 폭으로 감소하였고 탁도, 영양염류 및 규산 등과 같은 항목은 증가하는 양상을 보였다. 하절기 엽록소-a 농도는 총인, 총질소의 높은 농도에도 불구하고 연중 최저치를 나타냈는데, 이는 장마 강우로 인한 탁도 증가와 수체의 체류시간감소 영향 등이 크게 작용한 것으로 사료된다. 장마 초기 강우 동안 영양염류의 농도는 크게 증가하는 양상을　보였으나 항목에 따라 그 패턴은 다소 상이했다. 장마는　몬순기후에 의해 발생하는 기상 현상으로,　연중 가장 두드러진 집중된 강우 및 급격한 유량변화를 유발함으로써 하천생태계에 큰 영향을 미치게 된다. 특히, 이 기간동안 강우의 빈도 및 강도는 하천의 육수학적 현상 변화와 패턴에 중요한 요소로서 작용하며, 이는 동아시아몬순기후대에 속하는 하천들에서 유사하게 발생하는 하천의 중요한 특성으로 사료된다.

• 대기
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• 제32권4호
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• pp.367-379
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• 2022

In this paper, the evaluation of the performance of Korea Meteorological Administratio (KMA) Global Seasonal forecasting system version 6 (GloSea6) is presented by assessing the effects of larger ensemble size and carrying out the test using different initial conditions for hindcast in sub-seasonal to seasonal scales. The number of ensemble members increases from 3 to 7. The Ratio of Predictable Components (RPC) approaches the appropriate signal magnitude with increase of ensemble size. The improvement of annual variability is shown for all basic variables mainly in mid-high latitude. Over the East Asia region, there are enhancements especially in 500 hPa geopotential height and 850 hPa wind fields. It reveals possibility to improve the performance of East Asian monsoon. Also, the reliability tends to become better as the ensemble size increases in summer than winter. To assess the effects of using different initial conditions, the area-mean values of normalized bias and correlation coefficients are compared for each basic variable for hindcast according to the four initial dates. The results have better performance when the initial date closest to the forecasting time is used in summer. On the seasonal scale, it is better to use four initial dates, where the maximum size of the ensemble increases to 672, mainly in winter. As the use of larger ensemble size, therefore, it is most efficient to use two initial dates for 60-days prediction and four initial dates for 6-months prediction, similar to the current Time-Lagged ensemble method.

• 한국해양학회지:바다
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• 제24권4호
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• pp.509-518
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• 2019

다양한 표층 수온 자료를 통해 1979년부터 2018년 기간 동안의 가을철 동해 공간 평균 표층 수온이 태평양 순년 진동과 높은 상관관계를 나타내는 것을 확인하였다. 이 해역에서 제트류의 활동이 가장 강한 200 hPa에서의 바람과 동해 표층 수온의 회귀 분석 결과, 가을철 동해 표층 수온이 상승할 때 제트류의 중심축이 북상하면서 전반적으로 제트류가 약화하는 경향을 보이며, 동해 수온이 하강할 때는 제트류의 중심축이 남하하면서 제트류가 강화되는 경향을 보였다. 이러한 분석 결과는 제트류의 강도 변화와 중심축의 남북 진동이 동해 표층 수온과 태평양 순년 진동의 커플링과 관련되어 있음을 시사한다. 여름철의 약한 제트류와 겨울철 및 이른 봄철의 강한 동아시아 동계계절풍 효과는 동해와 태평양 순년 진동의 커플링이 가을철 외의 다른 계절에 잘 나타나지 않게 하는 이유로 생각해볼 수 있다.

• 대기
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• 제21권1호
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• pp.109-121
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• 2011

This study revisits the definition of Changma, which is the major rainy season in Korea and corresponds to a regional component of the East Asian summer monsoon system. In spite of several decades of researches on Changma, questions still remain on many aspects of Changma that include its proper definition, determination of its onset and retreat, and relevant large-scale dynamical and thermodynamical features. Therefore, this study clarifies the definition of Changma (which is a starting point for the study of interannual and interdecadal variability) using a basic concept of air mass and front by calculating equivalent potential temperature (${\theta}_e$) that considers air temperature and humidity simultaneously. A negative peak in the meridional gradient of this quantity signifies the approximate location of Changma front. This front has previously been recognized as the boundary between the tropical North Pacific air mass and cold Okhotsk sea air mass. However, this study identifies three more important air masses affecting Changma: the tropical monsoon air mass related to the intertropical convergence zone over Southeast Asia and South China Sea, the tropical continental air mass over North China, and intermittently polar continental air mass. The variations of these five air masses lead to complicated evolution of Changma and modulate intensity, onset and withdrawal dates, and duration of Changma on the interannual time scale. Importantly, use of ${\theta}_e$, 500-hPa geopotential height and 200 hPa zonal wind fields for determining Changma onset and withdrawal dates results in a significant increase (up to~57%) in the hindcast skill compared to a previous study.