• Atmosphere
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• v.22 no.4
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• pp.455-464
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• 2012

This study investigates a 12 month-lead predictability of PNU Coupled General Circulation Model (CGCM) V1.1 hindcast, for which an oceanic data assimilated initialization is used to generate ocean initial condition. The CGCM, a participant model of APEC Climate Center (APCC) long-lead multi-model ensemble system, has been initialized at each and every month and performed 12-month-lead hindcast for each month during 1980 to 2011. The 12-month-lead hindcast consisted of 2-5 ensembles and this study verified the ensemble averaged hindcast. As for the sea-surface temperature concerns, it remained high level of confidence especially over the tropical Pacific and the mid-latitude central Pacific with slight declining of temporal correlation coefficients (TCC) as lead month increased. The CGCM revealed trustworthy ENSO prediction skills in most of hindcasts, in particular. For atmospheric variables, like air temperature, precipitation, and geopotential height at 500hPa, reliable prediction results have been shown during entire lead time in most of domain, particularly over the equatorial region. Though the TCCs of hindcasted precipitation are lower than other variables, a skillful precipitation forecasts is also shown over highly variable regions such as ITCZ. This study also revealed that there are seasonal and regional dependencies on predictability for each variable and lead.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1147-1151
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• 2009

In this study, we address the problem of producing probability forecasts of summer seasonal rainfall, on the basis of Hindcast experiments from a ensemble of GCMs(cwb, gcps, gdaps, metri, msc_gem, msc_gm2, msc_gm3, msc_sef and ncep). An advanced Hierarchical Bayesian weighting scheme is developed and used to combine nine GCMs seasonal hindcast ensembles. Hindcast period is 23 years from 1981 to 2003. The simplest approach for combining GCM forecasts is to weight each model equally, and this approach is referred to as pooled ensemble. This study proposes a more complex approach which weights the models spatially and seasonally based on past model performance for rainfall. The Bayesian approach to multi-model combination of GCMs determines the relative weights of each GCM with climatology as the prior. The weights are chosen to maximize the likelihood score of the posterior probabilities. The individual GCM ensembles, simple poolings of three and six models, and the optimally combined multimodel ensemble are compared.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.4 no.2
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• pp.130-137
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• 1992

The previous model of Inchon Bay (Choi 1980) was refined to hindcast/forecast the tides in the Inchon Bay by prescribing the 8 tidal constituents at the open boundaries. A series of hindcast was performed for the period of meterologically calm condition and the simulated results were compared with limited observation showing the reasonable agreements. Preliminary stage of real-time tidal prediction over the whole Inchon Bay were briefly outlined for practical purposes. The established model were further improved by dynamically interfacing, a one dimensional representation of the Han River system. With this model the tidal propagation in the Han River were computed and simulation of recent September. 1990 flood were performed. Discussion for further model development are also described.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.5
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• pp.343-351
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• 2012

In this study, shallow-water design waves are calculated for the return period of 10, 20, 30, and 50 years, based on the extreme value analysis of the wave measurement data at Gangneung beach. These values are compared with the results of SWAN simulation with the boundary condition of the deep-water design waves of the corresponding return periods at the Gangneung sea area provided by the Fisheries Agency (FA, 1988) and Korea Ocean Research & Development Institute (KORDI, 2005). It is found that the shallow-water wave heights at Gangneung beach calculated by the deep-water design waves were significantly less than the observation data. As the return period becomes higher, the significant wave heights obtained by the extreme value analysis becomes higher than those computed by SWAN with the deep-water design waves of the corresponding return periods. KORDI computed the hindcast wave data from January 2004 to August 2008 by WAM with a finer-grid mesh system than those of previous studies. Comparisons of the wave hindcast results with the wave observation show that the reproducibility of the winter-season storm wave was considerably improved compared to the hindcast data from 1979 to 2003. Hereafter, it is necessary to carry out hindcast wave data for the years before 2004 using WAM with the finer-grid mesh system and to supplement the deep-water design wave.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2008.09a
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• pp.180-183
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• 2008

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2008.09b
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• pp.180-183
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• 2008

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.7 no.3
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• pp.100-107
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• 2002

The sea-surface winds during the passage of 64 typhoons for 1979-1999 were simulated using two different typhoon wind models, ie, typhoon parametric model(TPM) and primitive vortex model(PVM). The model hindcast winds were compared with the winds observed at JMA ocean buoys(22001 and 21002) and Kyushu ocean observation tower. The analysis of ms and relative errors between hindcast and observed winds was made to find the accuracy and sensitivity of the typhoon wind prediction models. Both hindcast winds of TPM and PVM underestimate the observed typhoon winds, but PVM winds are more closer to the observations with less rms and relative errors. Relative errors of two model winds were small within 200km from typhoon center, but TPM's relative errors increase up to 70% as the radial distance from typhoon center increases beyond > 200km although PVM's relative errors remain in 20% with less sensitive to the distance from typhoon centers.

• Atmosphere
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• v.28 no.4
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• pp.479-490
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• 2018

This study assesses the prediction skill of regional scale model for the mean temperature anomaly over South Korea produced by Pusan National University Coupled General Circulation Model (PNU CGCM)-Weather Research and Forecasting (WRF) chain. The initial and boundary conditions of WRF are derived from PNU CGCM. The hindcast period is 11 years from 2007 to 2017. The model's prediction skill of mean temperature anomaly is evaluated in terms of the temporal correlation coefficient (TCC), root mean square error (RMSE) and skill scores which are Heidke skill score (HSS), hit rate (HR), false alarm rate (FAR). The predictions of WRF and PNU CGCM are overall similar to observation (OBS). However, TCC of WRF with OBS is higher than that of PNU CGCM and the variation of mean temperature is more comparable to OBS than that of PNU CGCM. The prediction skill of WRF is higher in March and April but lower in October to December. HSS is as high as above 0.25 and HR (FAR) is as high (low) as above (below) 0.35 in 2-month lead time. According to the spatial distribution of HSS, predictability is not concentrated in a specific region but homogeneously spread throughout the whole region of South Korea.

• Atmosphere
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• v.32 no.4
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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.

• Atmosphere
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• v.31 no.5
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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.