• 한국지구과학회지
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• 제34권2호
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• pp.136-147
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• 2013

이 연구는 6월 남극진동이 한국 6월 강우량에 영향을 주는지 알아보기 위해 두 변수 사이에 상관분석이 이루어졌고 높은 양의 상관관계가 있음이 밝혀졌다. 이는 한국 6월 강우량이 같은 시기에 남반구에서 강화되는 머스커렌 고기압과 호주 고기압의 영향을 받음을 의미하는 것이다. 이 두 고기압이 발달할 때 호주 주위지역으로부터 적도방향으로 적도 횡단류가 강화되며, 이 적도 횡단류의 강화는 북태평양고기압의 북쪽으로의 강화로 이어진다. 이는 결국 장마전선을 한국으로 북상시키는 역할을 한다. 더욱이 북태평양 고기압의 북쪽으로의 강화는 한국에 상륙하거나 영향을 주는 태풍의 빈도를 증가시켜 6월 강우량의 증가에 중요한 역할을 한다.

• 대기
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• 제24권1호
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• pp.89-99
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• 2014

Recently, several studies pointed out that there are distinct two types of El Ni$\tilde{n}$o events based on the spatial pattern of SST. Since the two types of El Ni$\tilde{n}$o have different impacts on global climate, it is quite important to identify the type to assess and predict the regional climate variability. So far, however, there are still many different definitions to identify the two types of El Ni$\tilde{n}$o from the different studies. In this study, we investigated a sensitivity of the impacts on climate variability over the Korean Peninsula corresponding to the definition of two-types of El Ni$\tilde{n}$o. After checking pre-existing definitions and other possible definition, it is suggested here that two different definitions exhibit relatively strong relationship between El Ni$\tilde{n}$o events and the Korean climate variables when two types of El Ni$\tilde{n}$o are separated. In addition to the Korean climate, the two types of El Ni$\tilde{n}$o show quite distinct global teleconnection patterns when the definitions are used.

• 한국해안해양공학회지
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• 제19권5호
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• pp.467-475
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• 2007

기상청 현업 모델 RDAPS 모델 자료와 QuikSCAT 관측결과 중 2005, 2006년 해상풍 자료를 비교하였다. 해상풍의 하계와 동계의 평균 공간 분포의 분석결과 한반도 주변의 계절적인 해상풍의 뚜렷한 특성을 잘 나타낸다. 모델과 관측의 해상풍 통계 분석 비교에서도 계절적인 차이를 잘 나타낸다. 한반도 주변의 하계 BIAS 값은 -0.5m/s이하의 분포를 보이고, 동계에는 -1 m/s이하의 분포를 보인다. 상관계수의 경우 하계에는 0.7, 동계에는 0.8 이상으로 분포한다. 공간적으로 평균된 상관계수의 경우 2005년, 2006년 모두 하계보다 동계에 더욱 상관관계가 높은 것으로 나타났다. 이것은 하계의 약한 풍속보다 동계의 강한 해상풍을 RDAPS에서 더 잘 재현하고 있는 것으로 판단된다.

• 대한원격탐사학회지
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• 제34권1호
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• pp.101-115
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• 2018

The Long Valley area and its surroundings are part of a major volcano system where inflation occurred in the resurgent dome in the 1990s. We used ENVISAT data to monitor surface deformation of the Long Valley area and its surroundings after the inflation, from 2003-2010. To retrieve the time series of the deformation, we applied the refined Small BAseline Subset (SBAS) algorithm which is improved using an iterative approach to minimize unwrapping error. Moreover, ascending and descending data were used to decompose the horizontal and vertical deformation in detail. To confirm refined SBAS results, we used GPS dataset. The InSAR errors are estimated as ${\pm}1.0mm/yr$ and ${\pm}0.8mm/yr$ from ascending and descending tracks, respectively. Compare to the previous study of 1990s over the Long Valley and its surroundings, Paoha Island and CASA geothermal area still subside. The deformation pattern in the Long Valley area during the study period (2003-2010) went through both subsidence (2003-2007) and slow uplift(2007-2010) episodes. Our research also shows no deformation signal near McGee Creek. Our study provided a better understanding of the surface changes of the indicators in the 1990s and 2000s.

• 대한원격탐사학회지
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• 제36권4호
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• pp.587-607
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• 2020

Soil moisture is essential information for meteorological and hydrological analyses. To date, many efforts have been made to achieve the two goals for soil moisture data, i.e., the improvement of accuracy and resolution, which is very challenging. We presented an ensemble downscaling method for quality improvement of gridded soil moisture data in terms of the accuracy and the spatial resolution by the integration of BMA (Bayesian model averaging) and ATPRK (area-to-point regression kriging). In the experiments, the BMA ensemble showed a 22% better accuracy than the data sets from ESA CCI (European Space Agency-Climate Change Initiative), ERA5 (ECMWF Reanalysis 5), and GLDAS (Global Land Data Assimilation System) in terms of RMSE (root mean square error). Also, the ATPRK downscaling could enhance the spatial resolution from 0.25° to 0.05° while preserving the improved accuracy and the spatial pattern of the BMA ensemble, without under- or over-estimation. The quality-improved data sets can contribute to a variety of local and regional applications related to soil moisture, such as agriculture, forest, hydrology, and meteorology. Because the ensemble downscaling method can be applied to the other land surface variables such as temperature, humidity, precipitation, and evapotranspiration, it can be a viable option to complement the accuracy and the spatial resolution of satellite images and numerical models.

• 한국지능시스템학회논문지
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• 제24권6호
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• pp.586-591
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• 2014

본 연구에서는 인공 벌 군집(ABC: Artificial Bee Colony) 알고리즘을 이용하여 주어진 레이더 데이터로부터 강수 사례와 비강수 사례를 분류하는 방사형 기저함수 신경회로망(RBFNNs: Radial Basis Function Neural Networks)분류기를 소개한다. 기상청에서 사용하고 있는 기상 레이더 데이터의 특성 분석을 통해 입력 데이터를 구성한다. 방사형 기저함수 신경회로망의 조건부에서는 Fuzzy C-Means 클러스터링 방법을 이용하여 적합도를 계산하고, 결론부에서는 최소자승법(LSE: Least Square Method)을 이용하여 다항식 계수를 추정한다. 추론부에서 최종출력 값은 퍼지 추론 방법을 이용하여 얻어진다. 제안된 분류기의 성능은 기상청에서 사용하는 QC와 CZ 데이터를 고려하여 비교 및 분석되어진다.

• Wind and Structures
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• 제10권3호
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• pp.287-300
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• 2007

Wind action is a factor of fundamental importance in the structural design of light or slender constructions. Codes for structural design usually assume that the incident mean wind velocity is parallel to the ground, which constitutes a valid simplification for frequent winds caused by meteorological phenomena such as Extratropical Storms (EPS) or Tropical Storms. Wind effects due to other phenomena, such as thunderstorms, and its combination with EPS winds in so-called squall lines, are simply neglected. In this paper a model that describes the three-dimensional wind velocity field originated from a downburst in a thunderstorm (TS) is proposed. The model is based on a semi empirical representation of an axially-symmetrical flow line pattern that describes a stationary field, modulated by a function that accounts for the evolution of the wind velocity with time. The model allows the generation of a spatially and temporally variable velocity field, which also includes a fluctuating component of the velocity. All parameters employed in the model are related to meteorological variables, which are susceptible of statistical assessment. A background wind is also considered, in order to account for the translational velocity of the thunderstorm, normally due to local wind conditions. When the translation of the TS is caused by an EPS, a squall line is produced, causing the highest wind velocities associated with TS events. The resulting vertical velocity profiles were also studied and compared with existing models, such as the profiles proposed by Vicroy, et al. (1992) and Wood and Kwok (1998). The present model predicts horizontal velocity profiles that depend on the distance to the storm center, effect not considered by previous models, although the various proposals are globally compatible. The model can be applied in any region of interest, once the relevant meteorological variables are known, to simulate the excitation due to TS winds in the design of transmission lines, long-span crossings, cable-stayed bridges, towers or similar structures.

• 한국농공학회논문집
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• 제61권6호
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• pp.73-79
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• 2019

Continuous and tremendous data (canopy temperature and meteorological variables) are necessary to determine Crop Water Stress Index (CWSI). This study investigated the optimal monitoring time and interval of canopy temperature and meteorological variables (air temperature, relative humidity, solar radiation and wind speed) to determine CWSIs. The Nash-Sutcliffe model efficiency coefficient (NSE) was used to quantitatively describe the accuracy of sampling method depending upon various time intervals (t=5, 10, 15, 20, 30 and 60 minutes) and CWSIs per every minute were used as a reference. The NSE coefficient of wind speed was 0.516 at the sampling time of 60 minutes, while the ones of other meteorological variables and canopy temperature were greater than 0.8. The pattern of daily CWSIs increased from 8:00 am, reached the maximum value at 12:00 pm, then decreased after 2:00 pm. The statistical analysis showed that the data collection at 11:40 am produced the closest CWSI value to the daily average of CWSI, which indicates that just one time of measurement could be representative throughout the day. Overall, the findings of this study contributes to the economical and convenient method of quantifying CWSIs and irrigation management.

• 한국지구과학회지
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• 제42권6호
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• pp.605-622
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• 2021

Seasonal forecasting has numerous socioeconomic benefits because it can be used for disaster mitigation. Therefore, it is necessary to diagnose and improve the seasonal forecast model. Moreover, the model performance is partly related to the ocean model. This study evaluated the hindcast performance in the upper ocean of the Global Seasonal Forecasting System version 5-Global Couple Configuration 2 (GloSea5-GC2) using a multivariable integrated evaluation method. The normalized potential temperature, salinity, zonal and meridional currents, and sea surface height anomalies were evaluated. Model performance was affected by the target month and was found to be better in the Pacific than in the Atlantic. An increase in lead time led to a decrease in overall model performance, along with decreases in interannual variability, pattern similarity, and root mean square vector deviation. Improving the performance for ocean currents is a more critical than enhancing the performance for other evaluated variables. The tropical Pacific showed the best accuracy in the surface layer, but a spring predictability barrier was present. At the depth of 301 m, the north Pacific and tropical Atlantic exhibited the best and worst accuracies, respectively. These findings provide fundamental evidence for the ocean forecasting performance of GloSea5.

• 대기
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• 제24권1호
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• pp.123-130
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• 2014

계절예측시스템의 배경 지식이 부족한 사용자가 시스템을 효율적으로 구동하고 조절할 수 있도록 자동화에 최적화된 시스템을 기상청 국가태풍센터에 구축하였다. 기존 예측시스템에서 사용자의 주관이 포함되어 자동화 구축에 제약을 주는 군집분류와 예측인자 선정 과정은 미리 수행되고, 그 출력자료는 입력자료로서 제공된다. 시스템을 이해하고 운용하는데 도움을 주기 위해 기상청 규격에 따라 디렉토리 구조를 재구성하고, 해당 디렉토리에 포함되어 있는 입력자료와 소스코드를 이용해 산출되는 출력자료를 정리하였다. 또한 기존 예측시스템에서 고정되어 있거나 수동으로 설정해야 하는 구동조건을 효과적으로 조절하기 위해 네임리스트를 이용한 사용자인터페이스를 추가하여 자동화 시스템을 최적화하였다. 이러한 자동화 시스템에 의해 기술적으로 가능해진 조기예측의 성능을 검증한 결과, 예측시점을 5월에서 1월까지 앞당겨도 모든 진로유형에서 높은 예측성능이 유지되었다. 이처럼, 조기예측이 가능해진 태풍진로 계절예측시스템은 국가태풍센터의 현업예보뿐만 아니라 태풍계절예측 분야의 연구자에게도 매우 유익할 것으로 기대되고, 본 기술노트는 효율적인 예측시스템 운영을 위한 기술적 지침서로 활용될 것이다.