• 대한지리학회지
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• 제45권5호
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• pp.541-552
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• 2010

후기 플라이스토신 및 홀로신 시기 동아시아 여름 몬순의 변화를 밝히기 위해 지화학적 분석 방법(탄소동원원소(${\delta}^{13}C$), 탄질율(C/N), 대자율, 입도 분석 등)을 활용하여 서해안 염하구 습지 퇴적물을 분석하였다. 연구 결과에 따르면 한반도에서 여름 몬순은 7,700-7,800년 전에 정점이었고 7,400년 전 경부터 약화되기 시작한다. 그리고 마지막 빙하 최성기 중 24,000-24,500년 전 경에는 몬순이 상대적으로 약했고 18,500-19,500년 전 경에는 상대적으로 강했다. 염하구 습지 퇴적물의 지화학적 분석 자료는 과거 여름 몬순의 변동을 밝힐 수 있는 새로운 고환경 자료로서 가치를 갖는다. 특히 고환경 자료가 부족한 한국 학계에 큰 도움이 될 것으로 사료된다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 1999년도 Proceedings of International Symposium on Remote Sensing
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• pp.325-329
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• 1999

The characteristic of East Asian summer monsoon is investigated using 8-year (March 1987-February 1995) - averaged monthly and 5-day mean 1 degree latitude-longitude gridded GMS high-cloud-amount data (HCA). An analysis of these data shows the convective zone (ITCZ) clouds which defined as the percentage of the total grid area covered by clouds with a cloud-top temperature below the 400 hPa-level climatological temperature. The HCA increased clearly over equatorial zone during December and January and 30-40 $^{\circ}$N during May and June. These HCA patterns are coincided with seasonal cycles of summer monsoon which is introduced in historical references. The relationship with the summer monsoon winds as climatological changing of wind direction is analyzed by ECMWF re-analysis 2.5-degree latitude-longitude grid surface data which is calculated with 8-year averaged from January 1987 to January 1995. In addition, the monsoon winds are showed by separated U, V-wind components far manifestation a tendency of onset and retreat data of seasonal monsoon.

• 대기
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• 제31권5호
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• pp.563-576
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• 2021

The performance of East Asian summer monsoon is assessed for GC2 and GC3.1, which are climate change models of the current and next climate prediction system in the Korea Meteorological Administration (KMA), GloSea5 and GloSea6. The most pronounced characteristics of GC models are strong monsoon trough and the weakening of the Western North Pacific Subtropical High (WNPSH). These are related to the weakening of the southwesterly wind and resulting weak monsoon band toward the Korean Peninsula. The GC3.1 is known to have improved the model configuration version compared to GC2, such as cloud physics and ocean parameters. We can confirm that the overall improvements of GC3.1 against GC2, especially in pressure, 850 hPa wind fields, and vertical wind shear. Also, the precipitation band stagnant in the south of 30°N in late spring is improved, therefore the biases of rainy onset and withdrawal on the Korean Peninsula are reduced by 2~4 pentad. We also investigate the impact of initialization in comparison with GloSea5 hindcast. Compared with GCs, hindcast results show better simulation within 1 month lead time, especially in pressure and 850 hPa wind fields, which can be expected to the improvement of WNPSH. Therefore, it is expected that the simulation performance of WNPSH will be improved in the result of applying the initialization of GloSea6.

• 대기
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• 제27권2호
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• pp.133-150
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• 2017

This study evaluates CMIP5 model performance on rainy season evolution in the East Asian summer monsoon. Historical (1986~2005) simulation is analyzed using ensemble mean of CMIP5 19 models. Simulated rainfall amount is underestimated than the observed and onset and termination of rainy season are earlier in the simulation. Compared with evolution timing, duration of the rainy season is uncertain with large model spread. This area-averaged analysis results mix relative differences among the models. All model show similarity in the underestimated rainfall, but there are quite large difference in dynamic and thermodynamic processes. The model difference is shown in horizontal distribution analysis. BEST and WORST group is selected based on skill score. BEST shows better performance in northward movement of the rain band, summer monsoon domain. Especially, meridional gradient of equivalent potential temperature and low-level circulation for evolving frontal system is quite well captured in BEST. According to RCP8.5, CMIP5 projects earlier onset, delayed termination and longer duration of the rainy season with increasing rainfall amount at the end of 21st century. BEST and WORST shows similar projection for the rainy season evolution timing, meanwhile there are large discrepancy in thermodynamic structure. BEST and WORST in future projection are different in moisture flux, vertical structure of equivalent potential temperature and the subsequent unstable changes in the conditional instability.

• Ocean and Polar Research
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• 제27권3호
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• pp.289-297
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• 2005

The change in global climate and Asian monsoon patterns during the mid-Holocene, 6000 years before present (6 ka), is simulated by a climate model at spectral truncations of T170 with 18 vertical layers, corresponding to grid-cell sizes of roughly 75km. The present simulation is forced with the observed monthly data of sea surface temperatures, and the specified concentration of atmospheric carbon dioxide, while in the mid-Holocene experiment, orbital parameters such as obliquity, precession, and eccentricity are changed to the 6ka conditions. Under such conditions, the precipitation associated with the summer monsoon is enhanced over a wider zonal band from the Middle East to Southeast Asia, while no significant alteration takes Place in winter. The monsoonal wind also increases over the Arabian Sea, showing the enhanced southwesterly wind during summer and northeasterly wind during winter. Overall, the showing of the Asian monsoon is enhanced during the mid-Holocene, especially in summer, which is consistent with the proxy estimates and other previous model simulations.

• 한국지구과학회지
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• 제44권3호
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• pp.185-195
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• 2023

The prolonged and heavy East Asian summer precipitation in 2020 may have been caused by an enhanced Madden-Julian Oscillation (MJO), which requires evaluation using forecast models. We examined the performance of GloSea6, an operational forecast model, in predicting the East Asian summer precipitation during July 2020, and investigated the role of MJO in the extreme rainfall event. Two experiments, CON and EXP, were conducted using different convection schemes, 6A and 5A, respectively to simulate various aspects of MJO. The EXP runs yielded stronger forecasts of East Asian precipitation for July 2020 than the CON runs, probably due to the prominent MJO realization in the former experiment. The stronger MJO created stronger moist southerly winds associated with the western North Pacific subtropical high, which led to increased precipitation. The strengthening of the MJO was found to improve the prediction accuracy of East Asian summer precipitation. However, it is important to note that this study does not discuss the impact of changes in the convection scheme on the modulation of MJO. Further research is needed to understand other factors that could strengthen the MJO and improve the forecast.

• 대기
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• 제30권3호
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• pp.293-309
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• 2020

There are lots of indices that define the intensity of East Asian summer monsoon (EASM) in climate systems. This paper assesses the prediction skill for EASM indices in a Global Seasonal Forecasting System (GloSea5) that is currently operating at KMA. Total 5 different types of EASM indices (WNPMI, EAMI, WYI, GUOI, and SAHI) are selected to investigate how well GloSea5 reproduces them using hindcasts with 12 ensemble members with 1~3 lead months. Each index from GloSea5 is compared to that from ERA-Interim. Hindcast results for the period 1991~2010 show the highest prediction skill for WNPMI which is defined as the difference between the zonal winds at 850 hPa over East China Sea and South China Sea. WYI, defined as the difference between the zonal winds of upper and lower level over the Indian Ocean far from East Asia, is comparatively well captured by GloSea5. Though the prediction skill for EAMI which is defined by using meridional winds over areas of East Asia and Korea directly affected by EASM is comparatively low, it seems that EAMI is useful for predicting the variability of precipitation by EASM over East Asia. The regressed atmospheric fields with EASM index and the correlation with precipitation also show that GloSea5 best predicts the synoptic environment of East Asia for WNPMI among 5 EASM indices. Note that the result in this study is limited to interpret only for GloSea5 since the prediction skill for EASM index depends greatly on climate forecast model systems.

• 대한원격탐사학회지
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• 제14권1호
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• pp.1-16
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• 1998

미국 군사기상위성 프로그램의 SSM/I 센서에서 관측한 마이크로파 복사자료를 이용하여 대기수문변수 (수증기량, 구름수적량, 강수율)를 추정하였으며, 이 자료를 동아시아 하계 몬순의 특징을 파악하기 위해 활용하였다 한반도를 포함한 중국 북동부, 일본 지역에 가뭄현상이 나타났던 1994년과 정상적인 몬순활동을 보였던 1795년의 6, 7, 8월을 사례로 선택하였으며 분석영역은 (0$^{\circ}$-60$^{\circ}$N, 45$^{\circ}$-180$^{\circ}$E)의 아시아몬순 지역이다. 분석 결과 북위 20-30$^{\circ}$위도대에서 날짜변경선 부근으로부터 동아시아 몬순지역으로 건조한 영역 (적은 수증기 영역)의 서쪽이동이 약 20-30일 주기로 나타나고 있다. 건조지역의 서쪽 이동은 북태평양고기압의 동아시아몬순 지역으로의 확장을 의미하며, 결과적으로 동아시아 몬순지역에 수증기의 공급 등 대류활동을 증진시키는 요인을 제공하여 북태평양 고기압의 세력확장은 몬순의 진행에 영향을 주는 중요한 요인의 하나로 파악된다.

• 한국제4기학회지
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• 제20권1호
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• pp.9-27
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• 2006

이 연구는 동아시아 (중국, 한국, 그리고 일본) 여름몬순과 그 변동성을 MME (multi-model ensemble)을 이용하여 IPCC AR4 (Intergovernmental Panel on Climate Change Fourth Assessment Report) 실험의22개 접합 기후모델 결과 자료로 분석하였다. 결과자료들은 사용 가능한 모든 모델의 평균값을 이용하였다. 여름 몬순 기간 동안 최대 강수를 가지는 연주기는 모델에 의해 모의되었으나 장마(Meiyu-Changma-Baiu) 강수밴드의 이동(북쪽)과 연관되어 7월에 나타나는 최소값은 모의하지 못했다. MME 강수 패턴은 북태평양아열대 고기압과 장마전선대의 위치와 연관된 강수의 공간적 분포를 잘 나타내었다. 그러나 중국, 한반도, 그리고 일본의 동해와 인근 해역의 강수는 과소 예측되었다. 마지막으로 $CO_2$ 농도 배증시나리오의 복사 강제에 대한 미래예측을 분석하였다. MME는 $CO_2$ 농도가 배증될 때 동아시아지역에서 강수는 평균 7.8%로 나타났고, $5{\sim}10%$의 변화폭을 보였다. 그러나 이러한 강수의 증가는 통계적으로 한반도와 일본, 그리고 인근 북중국 지역에서만 중요한 의미를 가진다. 강수 예측에서 나타난 변화는 아열대 고기압의 강도 변화에 비례하는 것으로 나타났다. 그리고 봄에서 초가을까지 여름 몬순의 지속기간이 길어짐을 확인하였다.

• 대기
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• 제25권1호
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• pp.179-183
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• 2015

Even though state-of-the-art general circulation models is improved step by step, the seasonal predictability of the East Asian summer monsoon still remains poor. In contrast, the seasonal predictability of western North Pacific and Indian monsoon region using dynamic models is relatively high. This study builds canonical correlation analysis model for seasonal prediction using wind fields over western North Pacific and Indian Ocean from the Global Seasonal Forecasting System version 5 (GloSea5), and then assesses the predictability of so-called hybrid model. In addition, we suggest improvement method for forecast skill by introducing the lagged ensemble technique.