• Title/Summary/Keyword: Typhoon track

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Sea Surface Cooling in the East Sea with the Passage of Typhoons (태풍통과시 동해에서의 해수면 냉각현상)

  • HONG Chul-Hoon;SOHN Ik-Sung
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.37 no.2
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    • pp.137-147
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    • 2004
  • Sea surface cooling (SSC) with the passage of typhoons is examined in the East Sea using the Japan Meteorological Agency buoy data $(37^{\circ}45'N,\;134^{\circ}23'E)$ during 1983-2000 and a three-dimensional primitive equation model (the Princeton Ocean Model). Forty typhoons in this period induced the SST decrease ranging from about $-0.5^{\circ}C\;to\;-4.3^{\circ}C.$ Intense SSC $(<-2^{\circ}C)$ occurs with typhoons that passed mainly through the left-hand side of the buoy station. The model is implemented to examine a physical process of SSC with a typical-track typhoon in the northwestern Pacific $(24^{\circ}N\;to\;52^{\circ}N).$ The model well reproduces prominent features in the observation and addresses how it happens; SSC is induced mainly by momentum mixing effect stirred with the typhoon rather than upwelling.

The Characteristic of the Disasters caused by Typhoons passing through the Sea Area around the Korean Peninsula (한반도 주변 해역을 통과한 태풍의 재해특성)

  • Ahn, Suk-Hee;Choi, Ki-Seon;Kim, Baek-Jo;Shin, Seung-Sook
    • 한국방재학회:학술대회논문집
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    • 2008.02a
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    • pp.109-112
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    • 2008
  • The purpose of this study is to find out the characteristics of disasters caused by typhoons passing through the sea area around the Korean Peninsula. It analyzed two cases, that is, in WEST and EAST cases. These include the typhoons passing through the Yellow Sea, west of the Peninsula and East Sea, east of the Peninsula without landing on the Peninsula. FCM (Fuzzy Clustering Method) analysis was performed on typhoons affecting the Korean Peninsula from 1951 to 2006. The analysis shows that WEST case's cluster has the curved track of NE-S, and EAST case's cluster has the straight track of NE-SW. Typhoons that pass through the Yellow Sea have little change in frequency and the weak intensity. On the other hand, the frequency and the intensity of typhoons passing through the East Sea show the increasing trend. The characteristic of disasters by typhoons affecting the Korean Peninsula from 1973 to 2006 appears differently for each case: EAST cases caused significant damage in flooding, while WEST cases did damage in houses, ships, roads, and bridges. Rainfall amount and maximum wind speed data are analyzed in order to understand the impact of the typhoons, and the result indicates that the WEST cases are influenced by the wind, and East cases by precipitation. The result of this study indicates that the characteristic of disasters is distinctive according to the Typhoon's track. If applied to establish the disaster prevention plan, this result could make a contribution to the damage reduction.

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Investigation of Analysis Effects of ASCAT Data Assimilation within KIAPS-LETKF System (앙상블 자료동화 시스템에서 ASCAT 해상풍 자료동화가 분석장에 미치는 효과 분석)

  • Jo, Youngsoon;Lim, Sujeong;Kwon, In-Hyuk;Han, Hyun-Jun
    • Atmosphere
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    • v.28 no.3
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    • pp.263-272
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    • 2018
  • The high-resolution ocean surface wind vector produced by scatterometer was assimilated within the Local Ensemble Transform Kalman Filter (LETKF) in Korea Institute of Atmospheric Prediction Systems (KIAPS). The Advanced Scatterometer (ASCAT) on Metop-A/B wind data was processed in the KIAPS Package for Observation Processing (KPOP), and a module capable of processing surface wind observation was implemented in the LETKF system. The LETKF data assimilation cycle for evaluating the performance improvement due to ASCAT observation was carried out for approximately 20 days from June through July 2017 when Typhoon Nepartak was present. As a result, we have found that the performance of ASCAT wind vector has a clear and beneficial effect on the data assimilation cycle. It has reduced analysis errors of wind, temperature, and humidity, as well as analysis errors of lower troposphere wind. Furthermore, by the assimilation of the ASCAT wind observation, the initial condition of the model described the typhoon structure more accurately and improved the typhoon track prediction skill. Therefore, we can expect the analysis field of LETKF will be improved if the Scatterometer wind observation is added.

Analysis of Reliability of Weather Fields for Typhoon Maemi (0314) (태풍 기상장의 신뢰도 분석: 태풍 매미(0314))

  • Yoon, Sung Bum;Jeong, Weon Mu;Jho, Myeong Hwan;Ryu, Kyong Ho
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.32 no.5
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    • pp.351-362
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    • 2020
  • Numerical simulations of the storm surge and waves induced by the Typhoon Maemi incident on the south sea of Korea in 2003 are performed using the JMA-MSM forecast weather field, NCEP-CFSR reanalysis weather field, ECMWF-ERA5 reanalysis weather field, and the pressure and wind fields obtained using the best track information provided by JTWC. The calculated surge heights are compared with the time history observed at harbours along the coasts of Korea. For the waves occurring coincidentally with the storm surges the calculated significant wave heights are compared with the measured data. Based on the comparison of surge and wave heights the assessment of the reliability of various weather fields is performed. As a result the JMA-MSM weather fields gives the highest reliability, and the weather field obtained using JTWC best track information gives also relatively good agreement. The ECMWF-ERA5 gives in general surge and wave heights weaker than the measured. The reliability of NCEP-CFSR turns out to be the worst for this special case of Typhoon Maemi. Based on the results of this study it is found that the reliable weather fields are essential for the accurate simulation of storm surges and waves.

TIME SERIES PREDICTION USING INCREMENTAL REGRESSION

  • Kim, Sung-Hyun;Lee, Yong-Mi;Jin, Long;Chai, Duck-Jin;Ryu, Keun-Ho
    • Proceedings of the KSRS Conference
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    • v.2
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    • pp.635-638
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    • 2006
  • Regression of conventional prediction techniques in data mining uses the model which is generated from the training step. This model is applied to new input data without any change. If this model is applied directly to time series, the rate of prediction accuracy will be decreased. This paper proposes an incremental regression for time series prediction like typhoon track prediction. This technique considers the characteristic of time series which may be changed over time. It is composed of two steps. The first step executes a fractional process for applying input data to the regression model. The second step updates the model by using its information as new data. Additionally, the model is maintained by only recent data in a queue. This approach has the following two advantages. It maintains the minimum information of the model by using a matrix, so space complexity is reduced. Moreover, it prevents the increment of error rate by updating the model over time. Accuracy rate of the proposed method is measured by RME(Relative Mean Error) and RMSE(Root Mean Square Error). The results of typhoon track prediction experiment are performed by the proposed technique IMLR(Incremental Multiple Linear Regression) is more efficient than those of MLR(Multiple Linear Regression) and SVR(Support Vector Regression).

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Representation of Model Uncertainty in the Short-Range Ensemble Prediction for Typhoon Rusa (2002) (단기 앙상블 예보에서 모형의 불확실성 표현: 태풍 루사)

  • Kim, Sena;Lim, Gyu-Ho
    • Atmosphere
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    • v.25 no.1
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    • pp.1-18
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    • 2015
  • The most objective way to overcome the limitation of numerical weather prediction model is to represent the uncertainty of prediction by introducing probabilistic forecast. The uncertainty of the numerical weather prediction system developed due to the parameterization of unresolved scale motions and the energy losses from the sub-scale physical processes. In this study, we focused on the growth of model errors. We performed ensemble forecast to represent model uncertainty. By employing the multi-physics scheme (PHYS) and the stochastic kinetic energy backscatter scheme (SKEBS) in simulating typhoon Rusa (2002), we assessed the performance level of the two schemes. The both schemes produced better results than the control run did in the ensemble mean forecast of the track. The results using PHYS improved by 28% and those based on SKEBS did by 7%. Both of the ensemble mean errors of the both schemes increased rapidly at the forecast time 84 hrs. The both ensemble spreads increased gradually during integration. The results based on SKEBS represented model errors very well during the forecast time of 96 hrs. After the period, it produced an under-dispersive pattern. The simulation based on PHYS overestimated the ensemble mean error during integration and represented the real situation well at the forecast time of 120 hrs. The displacement speed of the typhoon based on PHYS was closest to the best track, especially after landfall. In the sensitivity tests of the model uncertainty of SKEBS, ensemble mean forecast was sensitive to the physics parameterization. By adjusting the forcing parameter of SKEBS, the default experiment improved in the ensemble spread, ensemble mean errors, and moving speed.

A Study on Typhoon Impacts in the Nakdong River Basin Associated with Decaying Phases of Central-Pacific El Niño (중앙태평양 엘니뇨의 쇠퇴특성에 따른 낙동강 유역의 태풍영향 분석)

  • Kim, Jong-Suk;Son, Chan-Young;Lee, Joo-Heon;Moon, Young-Il
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.34 no.1
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    • pp.135-143
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    • 2014
  • This study classified abnormal sea surface temperature changes of the central pacific region according to three evolution patterns. Focusing on typhoons that affect the Korean Peninsula, the research analyzed typhoon's occurrence spot and track, change in the central pressure characteristics, and the characteristics of change in typhoon precipitation and the number of occurrences of heavy rainfall in the Nakdong River Basin. As a result of analysis, in case of prolonged-decaying years and symmetric-decaying years, typhoon-related summer rainfall and heavy rainy days appeared to be higher than long-term average. But in case of abrupt-decaying years, the pattern of general decrease appeared. This is because typhoon's occurrence spot is located comparatively near the Korean peninsula, typhoon's central pressure is high, and typhoon's route generally moves to Japan. As the outcome, this study is expected to reduce flood damage through analyzing the characteristics of typhoon's activity according to CP El Ni$\tilde{n}$o evolution patterns and the characteristics of local typhoon rainfall. In addition, it is expected to provide useful information for establishing adaptation and mitigation to climate change.

Effect of Typhoons on Contaminants Released from the Southern Sea around Fukushima of Japan (일본 후쿠시마 근해에서 방출된 오염물질에 미치는 태풍의 영향)

  • Hong, Chul-Hoon;Kim, Jinpyo
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.49 no.2
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    • pp.234-240
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    • 2016
  • We examined the diffusion of contaminants released from the southern coast around Fukushima, Japan, during the passage of typhoons using a three-dimensional numerical model (POM) to track diffusing radioactivity (RA) released from the nuclear power plant at Fukushima following the accident caused by the giant tsunami event in March 2011. Radioactive contaminants released during the passage of typhoons may have significantly affected not only Japanese but also Korean coastal waters. The model domain covered most of the northwestern Pacific including marginal seas such as the East/Japan Sea and the Yellow Sea. Several numerical experiments were conducted case studies focusing on the westward diffusion from the southern coast of Japan of contaminants derived from the source site (Fukushima) according to various attributes of the typhoons, such as intensity, track, etc. The model produced the following results 1) significant amounts of contaminants were transported in a westward direction by easterly winds favorable for generating a coastal air stream along the southern Japanese coast, 2) the contaminants reached as far as Osaka Bay with the passage of typhoons, forced by a 5-day positive sinusoidal form with a (right-) northward track east of Fukushima, and 3) the range of contamination was significant, extending to the interior of the East/Japan Sea around the Tsugaru Strait. The model suggests that contaminants and/or radioactivity released from Fukushima with the passage of typhoons can affect Korean waters including the northeastern East/Japan Sea around the Tsugaru Strait, especially when the typhoon tracks are favorable for generating a westward coastal air stream along the southern Japanese coast.

Observing Sensitivity Experiment Based on Convective Scale Model for Upper-air Observation Data on GISANG 1 (KMA Research Vessel) in Summer 2018 (현업 국지모델기반 2018년 여름철 기상 1호 특별 고층관측자료의 관측 민감도 실험)

  • Choi, Dayoung;Hwang, Yoonjeong;Lee, Yong Hee
    • Atmosphere
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    • v.30 no.1
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    • pp.17-30
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    • 2020
  • KMA performed the special observation program to provide information about severe weather and to monitor typhoon PRAPIROON using the ship which called the Gisang 1 from 29 June 2018 to 4 July 2018 (UTC). For this period, upper-air was observed 21 times with 6 hour intervals using rawinsonde in the Gisang 1. We investigated the impact of upper-air observation data from the Gisang 1 on the performance of the operational convective scale model (we called LDAPS). We conducted two experiments that used all observation data including upper-air observation data from the Gisang 1 (OPER) and without it (EXPR). For a typhoon PRAPIROON case, track forecast error of OPER was lower than EXPR until forecast 24 hours. The intensity forecast error of OPER for minimum sea level pressure was lower than EXPR until forecast 12 hours. The intensity forecast error of OPER for maximum wind speed was mostly lower than EXPR until forecast 30 hours. OPER showed good performance for typhoon forecast compared with EXPR at the early lead time. Two precipitation cases occurred in the south of the Korean peninsula due to the impact of Changma on 1 July and typhoon on 3 July. The location of main precipitation band predicted from OPER was closer to observations. As assimilating upper-air data observed in the Gisang 1 to model, it showed positive results in typhoon and precipitation cases.