• 제목/요약/키워드: Model Uncertainties

검색결과 1,294건 처리시간 0.033초

기상청 고해상도 국지 앙상블 예측 시스템 구축 및 성능 검증 (Development and Evaluation of the High Resolution Limited Area Ensemble Prediction System in the Korea Meteorological Administration)

  • 김세현;김현미;계준경;이승우
    • 대기
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    • 제25권1호
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    • pp.67-83
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    • 2015
  • Predicting the location and intensity of precipitation still remains a main issue in numerical weather prediction (NWP). Resolution is a very important component of precipitation forecasts in NWP. Compared with a lower resolution model, a higher resolution model can predict small scale (i.e., storm scale) precipitation and depict convection structures more precisely. In addition, an ensemble technique can be used to improve the precipitation forecast because it can estimate uncertainties associated with forecasts. Therefore, NWP using both a higher resolution model and ensemble technique is expected to represent inherent uncertainties of convective scale motion better and lead to improved forecasts. In this study, the limited area ensemble prediction system for the convective-scale (i.e., high resolution) operational Unified Model (UM) in Korea Meteorological Administration (KMA) was developed and evaluated for the ensemble forecasts during August 2012. The model domain covers the limited area over the Korean Peninsula. The high resolution limited area ensemble prediction system developed showed good skill in predicting precipitation, wind, and temperature at the surface as well as meteorological variables at 500 and 850 hPa. To investigate which combination of horizontal resolution and ensemble member is most skillful, the system was run with three different horizontal resolutions (1.5, 2, and 3 km) and ensemble members (8, 12, and 16), and the forecasts from the experiments were evaluated. To assess the quantitative precipitation forecast (QPF) skill of the system, the precipitation forecasts for two heavy rainfall cases during the study period were analyzed using the Fractions Skill Score (FSS) and Probability Matching (PM) method. The PM method was effective in representing the intensity of precipitation and the FSS was effective in verifying the precipitation forecast for the high resolution limited area ensemble prediction system in KMA.

CMIP5 MME와 Best 모델의 비교를 통해 살펴본 미래전망: I. 동아시아 기온과 강수의 단기 및 장기 미래전망 (Future Change Using the CMIP5 MME and Best Models: I. Near and Long Term Future Change of Temperature and Precipitation over East Asia)

  • 문혜진;김병희;오효은;이준이;하경자
    • 대기
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    • 제24권3호
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    • pp.403-417
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    • 2014
  • Future changes in seasonal mean temperature and precipitation over East Asia under anthropogenic global warming are investigated by comparing the historical run for 1979~2005 and the Representative Concentration Pathway (RCP) 4.5 run for 2006~2100 with 20 coupled models which participated in the phase five of Coupled Model Inter-comparison Project (CMIP5). Although an increase in future temperature over the East Asian monsoon region has been commonly accepted, the prediction of future precipitation under global warming still has considerable uncertainties with a large inter-model spread. Thus, we select best five models, based on the evaluation of models' performance in present climate for boreal summer and winter seasons, to reduce uncertainties in future projection. Overall, the CMIP5 models better simulate climatological temperature and precipitation over East Asia than the phase 3 of CMIP and the five best models' multi-model ensemble (B5MME) has better performance than all 20 models' multi-model ensemble (MME). Under anthropogenic global warming, significant increases are expected in both temperature and land-ocean thermal contrast over the entire East Asia region during both seasons for near and long term future. The contrast of future precipitation in winter between land and ocean will decrease over East Asia whereas that in summer particularly over the Korean Peninsula, associated with the Changma, will increase. Taking into account model validation and uncertainty estimation, this study has made an effort on providing a more reliable range of future change for temperature and precipitation particularly over the Korean Peninsula than previous studies.

화재시뮬레이션에서 입력변수 및 모델 불확실도가 고려된 허용피난시간(ASET)에 관한 연구 (Study on the Available Safe Egress Time (ASET) Considering the Input Parameters and Model Uncertainties in Fire Simulation)

  • 한호식;황철홍
    • 한국화재소방학회논문지
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    • 제33권3호
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    • pp.112-120
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    • 2019
  • 국내 PBD에서 화재시뮬레이션을 이용한 안전성 평가의 신뢰성을 개선시키기 위하여, 화재시뮬레이션의 입력변수 및 수치모델의 불확실도가 고려된 ASET의 평가방법에 대한 검토가 수행되었다. 이를 위해 영화관 및 오피스텔이 검토 대상으로 선정되었다. 주요 결과는 다음과 같다. 인명안전기준에 제시된 주요 물리량에 가장 큰 영향을 미치는 열발생률의 불확실도를 고려할 때, 온도, CO 및 가시도의 상당한 변화가 발생됨을 확인하였다. 또한 수치모델의 불확실도를 반영한 편향인자를 고려할 때, 온도 및 CO는 큰 변화가 없으나 FDS의 낮은 연기농도 예측성능으로 인하여 가시도는 크게 증가됨을 알 수 있었다. 마지막으로 국내 PBD에서 ASET이 대부분 가시도에 의해 결정되는 원인이 논의되었으며, 정확한 ASET 평가를 위해 화재시뮬레이션의 입력변수 및 수치모델의 불확실도 적용 방안이 제안되었다.

A probabilistic framework for drought forecasting using hidden Markov models aggregated with the RCP8.5 projection

  • Chen, Si;Kwon, Hyun-Han;Kim, Tae-Woong
    • 한국수자원학회:학술대회논문집
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    • 한국수자원학회 2016년도 학술발표회
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    • pp.197-197
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    • 2016
  • Forecasting future drought events in a region plays a major role in water management and risk assessment of drought occurrences. The creeping characteristics of drought make it possible to mitigate drought's effects with accurate forecasting models. Drought forecasts are inevitably plagued by uncertainties, making it necessary to derive forecasts in a probabilistic framework. In this study, a new probabilistic scheme is proposed to forecast droughts, in which a discrete-time finite state-space hidden Markov model (HMM) is used aggregated with the Representative Concentration Pathway 8.5 (RCP) precipitation projection (HMM-RCP). The 3-month standardized precipitation index (SPI) is employed to assess the drought severity over the selected five stations in South Kore. A reversible jump Markov chain Monte Carlo algorithm is used for inference on the model parameters which includes several hidden states and the state specific parameters. We perform an RCP precipitation projection transformed SPI (RCP-SPI) weight-corrected post-processing for the HMM-based drought forecasting to derive a probabilistic forecast that considers uncertainties. Results showed that the HMM-RCP forecast mean values, as measured by forecasting skill scores, are much more accurate than those from conventional models and a climatology reference model at various lead times over the study sites. In addition, the probabilistic forecast verification technique, which includes the ranked probability skill score and the relative operating characteristic, is performed on the proposed model to check the performance. It is found that the HMM-RCP provides a probabilistic forecast with satisfactory evaluation for different drought severity categories, even with a long lead time. The overall results indicate that the proposed HMM-RCP shows a powerful skill for probabilistic drought forecasting.

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과거강우사상과 저류함수모형을 이용한 대유역 계획홍수량 추정 (Design Flood Estimation using Historical Rainfall Events and Storage Function Model in Large River Basins)

  • 윤종우;이동률;안원식;임해욱
    • 대한토목학회논문집
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    • 제29권3B호
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    • pp.269-279
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    • 2009
  • 대유역에서 계획홍수량 추정은 ARF, 강우 시공간분포 및 강우-유출 모형의 매개변수 등에서 많은 불확실성이 발생한다. 과거 동시 강우사상을 이용한 계획홍수량의 추정은 이들 불확실성을 개선할 수 있다. 본 연구는 과거 동시 강우사상과 저류 함수모형을 이용하여 대유역의 홍수량을 추정하는 방법을 제시하였다. 과거 동시 강우사상의 시공간분포를 이용하여 계획 강우량과 강우의 시공간분포를 산정하였고 비선형 강우-유출 반응을 재현할 수 있는 저류함수모형을 이용하여 홍수량을 추정하였다. 추정된 계획홍수량은 실측홍수량에 의한 빈도분석 결과와 비교하여 본 연구에서 제시한 홍수량 추정기법의 적용성을 평가하였다. 본 연구의 결과는 실측홍수량의 빈도해석과 비슷한 결과를 얻었으며 이는 대유역의 홍수량 추정에서 본 연구의 홍수량 추정과정을 충분히 이용할 수 있음을 보여준다.

인터넷 뱅킹에서 오프라인 신뢰와 온라인 거래의 관계 (The Relationship between Offline Trust and Online Transaction in Internet Banking)

  • 이웅규
    • Asia pacific journal of information systems
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    • 제17권2호
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    • pp.29-47
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    • 2007
  • Owing to the rapid growth of using the Internet, not only click-and-mortar companies but also brick-and-mortar ones have been expanding their distribution channels into online, Moreover, since online channels are more attractive than offline ones in control and maintenance, switching customers into online ones is emerged as one of very important managerial issues in a view of reduction of cost as well as expansion of services. However, the switched customers should be faced by uncertainties which could not have been experienced in offline. Specifically, in online channels, buyers and sellers are separated temporally and spacially and there are always so many kinds of threat for security as well as not enough systems and conventions for them yet. Therefore, trust has been considered as one of the most critical mechanisms for resolution of such uncertainties in online transactions. However, it is not easy to build and maintain the relationships in online since most of them are virtual and indirect generally. Therefore, in order to switch offline customers into online ones, it is very important to make strategies based on identification of the relationship between online transaction and offline trust which has been built in offline business. Generally offline trust, which has been built independent of online, could not include trust for online-dependent activities such as payment security during or after transactions, while most of online trust include it. Therefore, a customer with high offline trust does not always perceive high security and assure safe transactions. Accordingly, while online trust, where technical capabilities for online security is one of main bases, includes control trust implicitly or explicitly, offline trust does not. However. in spite of such clear discrimination and independence between offline trust and perceived security, there can be the significant dependency between these two beliefs. The customers with high offline trust believe that the company would do some activities for online security for customers' safe transactions since it has been believed of doing well for customers' trust. Theoretically, users' perception of security is interpreted as a kind of control trus, which is trust for company's technical control capacities in order to resolve technical uncertainties in online. Therefore, the relationship between two beliefs can be considered as transference from offline trust to another type trust. that is, control trust. The objective of this study is to analyze the effect of offline trust on online transaction uses mediated by perceived security. For this purpose, we suggest a research model based on technology acceptance model (TAM). Reuse intention is adopted as a dependent variable and TAM is modified by adding perceived risk (PR) as well as two beliefs of using Internet banking, perceived usefulness (PU) and perceived ease of use (PEOU). Moreover, perceive security (PS) is adopted as an external variable for PR and PU, while offline trust (OT) is an antecedent of PS. For an empirical test, sampling from 108 visitors to the banks in Daegu, Korea, we analyze our model by partial least square (PLS) approach. In result, our model is shown to explain 51.4% of the variance in reuse intention and all hypothesis are supported statistically. A theoretical implication of this study is to identify a role of PS between offline trust and reuse intention of using online transaction services. According to our result, PS can be considered as a mediation variable for bridging between two different concepts: trust that explains social aspects of customers and companies, and TAM that explains customers' reuse intention.

대용량 이력자료를 활용한 다중시간대 고속도로 교통량 예측 (Multiple Period Forecasting of Motorway Traffic Volumes by Using Big Historical Data)

  • 장현호;윤병조
    • 대한토목학회논문집
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    • 제38권1호
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    • pp.73-80
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    • 2018
  • 고속도로 교통류 제어는 기존의 Reactive 방식(실시간 대응)에서 Proactive 방식(사전 대응)으로 발전하고 있다. 첨단 고속도로 교통류 제어의 핵심 입력자료 중 하나는 여러 시간대에 걸치는 장래 교통량 상태이다. 다중 시간대 교통량 예측을 위해서는 장래 상태의 불확실성을 극복해야 한다. 이는 예측 시간대의 확장에 따라 장래 상태의 불확실성은 증가하기 때문이다. 따라서 다중 시간대 교통량 예측을 위해서는 장래 상태의 불확실성을 효과적으로 극복할 수 있는 실행 가능한 방안이 필요하다. 본 연구에서는 대용량 이력자료에 내재된 교통류 상태의 시간적 진화 행태를 이용하여 장래 상태의 불확실성을 효과적으로 극복함으로써 다중 시간대 장래 교통량 상태를 예측하는 모형을 제시하도록 한다. 개발 모형은 현행 교통량의 상태 진화를 기반으로 대용량 자료에 내재된 과거 상태를 추출하고, 이를 이용하여 장래 상태를 예측한다. 추가로, 개발된 모형은 실제 적용을 고려하여 자료관리시스템에 적합하도록 설계되었다. 적용결과, 개발모형은 다중 시간대에 걸치는 불확실성을 효과적으로 극복함으로써 우수한 예측력을 보였으며, 첨단자료관리시스템에 실제 적용이 가능하다고 판단된다.

Evaluation of a Fungal Spore Transportation in a Building under Uncertainty

  • Moon, Hyeun Jun
    • Architectural research
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    • 제8권1호
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    • pp.37-45
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    • 2006
  • A fungal spore transportation model that accounts for the concentration of airborne indoor spores and the amount of spores deposited on interior surfaces has been developed by extending the current aerosol model. This model is intended to be used for a building with a mechanical ventilation system, and considers HVAC filter efficiency and ventilation rate. The model also includes a surface-cleaning efficiency and frequency that removes a portion of spores deposited on surfaces. The developed model predicts indoor fungal spore concentration and provides an indoor/outdoor ratio that may increase or decrease mold growth risks in real, in-use building cases. To get a more useful outcome from the model simulation, an uncertainty analysis has been conducted in a real building case. By including uncertainties associated with the parameters in the spore transportation model, the simulation results provide probable ranges of indoor concentration and indoor/outdoor ratio. This paper describes the uncertainty quantification of each parameter that is specific to fungal spores, and uncertainty propagation using an appropriate statistical technique. The outcome of the uncertainty analysis showed an agreement with the results from the field measurement with air sampling in a real building.

Output feedback model predictive control for Wiener model with parameter dependent Lyapunov function

  • Yoo, Woo-Jong;Ji, Dae-Hyun;Lee, Sang-Moon;Won, Sang-Chul
    • 제어로봇시스템학회:학술대회논문집
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    • 제어로봇시스템학회 2005년도 ICCAS
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    • pp.685-689
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    • 2005
  • In this paper, we consider a robust output feedback model predictive controller(MPC) design for Wiener model. Nonlinearities that couldn't be represented in static nonlinearity block of Wiener model are regarded as uncertainties in linear block. An dynamic output feedback controller design method is presented for Wiener MPC. According to MPC algorithm, the control law is computed based on linear matrix inequality(LMI)at each sampling time by solving convex optimization. Also, a new parameter dependent Lyapunov function is proposed to get a less conservative condition. The results are illustrated with numerical example.

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Large Robust Designs for Generalized Linear Model

  • Kim, Young-Il;Kahng, Myung-Wook
    • Journal of the Korean Data and Information Science Society
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    • 제10권2호
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    • pp.289-298
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    • 1999
  • We consider a minimax approach to make a design robust to many types or uncertainty arising in reality when dealing with non-normal linear models. We try to build a design to protect against the worst case, i.e. to improve the "efficiency" of the worst situation that can happen. In this paper, we especially deal with the generalized linear model. It is a known fact that the generalized linear model is a universal approach, an extension of the normal linear regression model to cover other distributions. Therefore, the optimal design for the generalized linear model has very similar properties as the normal linear model except that it has some special characteristics. Uncertainties regarding the unknown parameters, link function, and the model structure are discussed. We show that the suggested approach is proven to be highly efficient and useful in practice. In the meantime, a computer algorithm is discussed and a conclusion follows.

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