• Journal of Astronomy and Space Sciences
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• 제31권1호
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• pp.91-99
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• 2014

The atmospheric flow in the 3-Cell model of global atmosphere circulation is described by the Lagrange's equation of the non-inertial frame where pressure force, frictional force and fictitious force are mixed in complex form. The Coriolis force is an important factor which requires calculation of fictitious force effects on atmospheric flow viewed from the rotating Earth. We make new Mathematica platform to solve Lagrange's equation by numerical analysis in order to analyze dynamics of atmospheric general circulation in the non-inertial frame. It can simulate atmospheric circulation process anywhere on the earth. It is expected that this pedagogical platform can be utilized to help students studying the atmospheric flow understand the mechanisms of atmospheric global circulation.

• 한국환경과학회지
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• 제4권5호
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• pp.403-411
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• 1995

The atmospheric responses to a Sea Surface Temperature Anomaly(SSTA) over the equatorial eastern Pacific Ocean have been investigated using the horizontally fine resolution model based on OSU 2-layer Atmospheric General Circulation Model(AGCM). The SSTAS daring the peak phase of 1982-83 El Nino have been applied to the model as the boundary conditions of the experiment. The model simulates the eastward movement of the rising branch of the Walker circulation. That is, the major features associated with the El Nino such as the increase of the precipitation rate over the center of the Pacific and decrease over the Indonesia, and the 500hPa geopotential height anomaly in the middle latitude are properly describes in the fine resolution model experiment. The model results indicate that this horizontally fine resolution UM can successfully simulate the ENSO anomalies and be more effectivelly used for the study of the climate and the climate changes.

• 한국기후변화학회지
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• 제34권12호
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• pp.5081-5092
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• 2021

Paleoproxy records indicate that abrupt changes in thermohaline circulation (THC) were induced by rapid meltwater discharge from retreating ice sheets. Such abrupt changes in the THC have been understood as a hysteresis behavior of a nonlinear system. Previous studies, however, primarily focused on a near-static hysteresis under fixed or slowly varying freshwater forcing (FWF), reflecting the equilibrated response of the THC. This study aims to improve the current understanding of transient THC responses under rapidly varying forcing and their dependency on forcing time scales. The results simulated by an Earth system model suggest that the bifurcation is delayed as the forcing time scale is shorter, causing the Atlantic meridional overturning circulation collapse and recovery to occur at higher and lower FWF values, respectively. The delayed shutdown/recovery occurs because bifurcation is determined not by the FWF value at the time but by the total amount of freshwater remaining over the THC convection region. The remaining freshwater amount is primarily determined by the forcing accumulation (i.e., time-integrated FWF), which is modulated by the freshwater/salt advection by ocean circulations and freshwater flux by the atmospheric hydrological cycle. In general, the latter is overwhelmed by the former. When the forced freshwater amount is the same, the modulation effect is stronger under slowly varying forcing because more time is provided for the feedback processes.

• 한국환경과학회지
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• 제4권5호
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• pp.17-17
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• 1995

• 한국지구과학회지
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• 제40권3호
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• pp.203-211
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• 2019

대기 대순환을 결정하는 주요 인자로는 남북방향 온도 경도와, 지구 자전으로 인한 코리올리 힘이 있다. 남북방향 온도 경도에 따른 경압성 차이로 인한 대기 대순환의 변화는 지금까지 많이 연구되어 왔으나, 자전속도에 따른 대기 대순환의 반응은 크게 연구되어 오지 않았다. 때문에 본 연구에서는 현 지구보다 느리거나 빠른 자전속도 범위를 모두 포괄하여 이에 따른 해들리 순환과 제트의 변화를 확인하였다. 이 연구에서 우리는 지구의 자전속도가 빨라질수록 해들리 순환 경계와 제트의 위치가 적도에 가까워지고, 제트와 해들리 순환의 세기가 약해진다는 것을 발견하였다. 해들리 순환 경계와 제트의 위치는 자전속도가 매우 빠르거나 느린 경우를 제외하면 준선형적인 관계를 가졌다. 특히, 해들리 순환 경계는 자전속도가 현재보다 1/8에서 8배의 자전속도 범위에서 자전속도보다 그 제곱근에 더 잘 반비례하는 경향성을 보였다. 단, 이러한 자전속도에 따른 변화는 해들리 순환 세기와 제트의 세기에 대해서는 뚜렷하지 않았다. 이는 대기 대순환의 위치 구조 변화는 지구 자전속도와 관련이 큰 반면, 세기의 변화는 자전속도로 설명되지 않음을 의미한다.

• Ocean and Polar Research
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• 제35권3호
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• pp.249-258
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• 2013

Vertical and horizontal mixing processes in the ocean mixed layer determine sea surface temperature and temperature variability. Accordingly, simulating these processes properly is crucial in order to obtain more accurate climate simulations and more reliable future projections using an ocean general circulation model (OGCM). In this study, by using Modular Ocean Model version 4 (MOM4) developed by Geophysical Fluid Dynamics Laboratory, the upper ocean temperature and mixed layer depth were simulated with two different vertical mixing schemes that are most widely used and then compared. The resultant differences were analyzed to understand the underlying mechanism, especially in the Tropical Pacific Ocean where the differences appeared to be the greatest. One of the schemes was the so-called KPP scheme that uses K-Profile parameterization with nonlocal vertical mixing and the other was the N scheme that was rather recently developed based on a second-order turbulence closure. In the equatorial Pacific, the N scheme simulates the mixed layer at a deeper level than the KPP scheme. One of the reasons is that the total vertical diffusivity coefficient simulated with the N scheme is ten times larger, at maximum, in the surface layer compared to the KPP scheme. Another reason is that the zonal current simulated with the N scheme peaks at a deeper ocean level than the KPP scheme, which indicates that the vertical shear was simulated on a larger scale by the N scheme and it enhanced the mixed layer depth. It is notable that while the N scheme simulates a deeper mixed layer in the equatorial Pacific compared to the KPP scheme, the sea surface temperature (SST) simulated with the N scheme was cooler in the central Pacific and warmer in the eastern Pacific. We postulated that the reason for this is that in the central Pacific atmospheric forcing plays an important role in determining SST and so does a strong upwelling in the eastern Pacific. In conclusion, what determines SST is crucial in interpreting the relationship between SST and mixed layer depth.

• 한국지구과학회지
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• 제27권6호
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• pp.653-658
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• 2006

대기 대순환 모형인 GCPS를 이용하여 북서태평양에서의 태풍 활동의 계절 예측 가능성을 조사하였다. 1979년부터 2003년까지 각 해에 대해 해수면 온도 관측 자료를 사용하여 5개월간 초기 조건을 달리한 10개의 앙상블 멤버를 적분하였다. 모형은 발생 빈도의 평균적인 월변화 경향과 발생 분포를 관측과 유사하게 모의하였으나, 발생 빈도의 경년 변화는 신빙성 있게 예측하지 못하였다. 이는 관측과 모형간 태풍 발생 빈도와 ENSO의 상관성 차이에 인한 것으로 실제 태풍 발생 빈도와 ENSO가 뚜렷한 상관 관계를 갖지 않는 것과 달리, 모형에서는 엘니뇨 시기에 평년에 비해 많은 태풍이 발생하고 라니냐 시기에 평년에 비해 적은 태풍이 발생하는 경향을 보였기 때문이다. 반면에, 관측과 모형 모두 ENSO와의 상관 관계가 높게 나타난 태풍 발생 경도의 경우에는 모형이 발생 경도의 경년 변화를 관측과 유사하게 모의하였다.

• Ocean and Polar Research
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• 제24권1호
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• pp.1-18
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• 2002

Seasonal variation in global transport calculated from an ocean general circulation model (OGCM) has been assessed through the comparison with observational estimates. The OGCM based on the GFDL MOM1.1 has honzontal grid interval of 10 and 21 verticle levels, and was integrated for 31 years forced by climatological wind stress, freshwater flux, and heat flux with restoring. General features of the world ocean circulation are well reproduced, which include the western boundary currents such as the Kuroshio and the Agulhas Current, the Equatorial Current system, the Antarctic Circumpolar Current, and the Weddell Sea gyres. Also well resolved is the remarkable seasonal variation in the depth-integrated flows in the northern Indian Ocean due to the monsoonal wind. Monthly variation is found to be dominant in the transport of the Antarctic Circumpolar Current through the Drake Passage in accordance with observational estimates. It has been shown that the mid-latitude depth-integrated flows obey the Sverdrup relation, except for some regions such as continental shelf regions where the interaction between stratification and bottom topography is critical.

• 대기
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• 제20권4호
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• pp.451-466
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• 2010

This edition has continued since 2006 tropical cyclone season our effort to provide standard tropical cyclone summaries by the western North Pacific basin and detailed reviews of operationally or meteorologically significant tropical cyclones to document significant challenges and shortfalls in the tropical cyclone warning system to serve as a focal point for research and development efforts. The tropical cyclone season of 2009 in the western North Pacific basin is summarized and the main characteristics of general atmospheric circulation are described. Also, the official track and intensity forecasts of these cyclones are verified. The total number is less than 59-year (1951~2009) average frequency of 26.4. The 2009 western North Pacific season was an inactive one, in which 22 tropical storms generated. Of these, 13 TCs reached typhoon (TY) intensity, while the rest 9 TCs only reached severe tropical storm (STS) and tropical storm (TS) intensity - three STS and six TS storms. On average of 22 TCs in 2009, the Korea Meteorological Administration official track forecast error for 48 hours was 219 km. There was a big challenge for individual cyclones such as 0902 CHAN-HOM, 0909 ETAU, and 0920 LUPIT resulting in significant forecast error, with both intricate tracks and irregular moving speed. There was no tropical cyclone causing significant direct impact to the country. The tropical cyclone season in 2009 began in May with the formation of KUJIRA (0901). In September and October, ten TSs formed in the western North Pacific in response to enhanced convective activity. On the other hand, the TC activity was very weak from June to July. It is found that the unusual anti-cyclonic circulation in the lower level and weak convection near the Philippines are dominant during summertime. The convection and atmospheric circulation in the western North Pacific contributed unfavorable condition for TC activity in the 2009 summertime. Year 2009 has continued the below normal condition since mid 1990s which is apparent in the decadal variability in TC activity.

• 한국해양학회지:바다
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• 제3권1호
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• pp.16-24
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• 1998

본 연구에서는 해양-대기 접합기후계의 연구를 위해 대기대순환모형에 대응하는 해양대순환모형을 개발하였고 이 해양대순환모형을 이용하여 주어진 대기경계조건에 대한 해양의 반응을 연구하였다. 기후학적 월평균값을 이용하여 모형을 100년동안 적분하였을 때(EXP 1), 해수온과 해류 등 모사된 대규모 해양상태는 관측과 유사하게 나타났다. 그러나 북적도반류와 같은 좁은 구역의 해류는 모형이 성긴 격자를 사용함으로 불가피하게 흐트러졌다. 남극주변의 남빙양상의 해빙의 계절변화 또한 잘 모사되었다. NCEP/NCAR Reanalysis Project로부터 얻어진 10년 월평균자료(1982-1991)를 경계조건으로 한 EXP 2에서 모형은 1982-1983과 1986-1987의 엘니뇨를 포함하는 그 기간 동안의 주요한 해양변화를 적절히 모사해 내었다. ENSO기간 동안 모형은 편서풍 아노말리의 동진에 따른 서향류 아노말리에 반응하여 동쪽으로 팽창하는 더운물과 적도를 따른 음의 연직속도 아노말리를 보여주고 있다. 엘니뇨와 상관한 아노말리 분포와 그 시간전개는 관측과 일치하고 있다. 일련의 실험들은 본 모형이 해양의 평균상태 및 아노말리를 재생산하는 능력을 가지고 있고, 해양-대기 결합계의 연구를 위해 효과적으로 사용될 수 있음을 보여준다.