• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.53 no.4
• /
• pp.637-649
• /
• 2020

An ideal 3D primitive equation model is implemented to investigate upper ocean response to typhoons, focusing on rightward bias (RWB) which means an appearance of an intensified sea surface cooling to the right side of the typhoon track. The model has 26-stratified levels and a flat bottom (1000 m), covering a rectangular domain of about 3,060 km×3,300 km with four open boundaries. The sea water is forced by an atmospheric pressure and a gradient wind of the typhoon. The model well reproduces the RWB in previous observations and theoretical analyses. For the fast moving typhoon (FMT) (-8m/sec), the model shows that in the mixed layer (ML), the RWB in the SST noticeably appears clearly illustrating the coupling between inertial motion and wind stress, but in the subsurface layer (-100m), the RWB does not emerge since a cyclonic current field (CCF) caused by wind stress curl is primarily dominant. For the slowly moving typhoon (SMT) (-3m/sec), however, the RWB does not emerge because the coupling is weakened and the CCF is rather predominant even in the ML. In the model, we conclude that the RWB noticeably emerges in the FMT but does not emerge in the SMT related to predominance of CCF.

• Journal of Environmental Science International
• /
• v.30 no.9
• /
• pp.763-777
• /
• 2021

The spatial characteristics of typhoon-class strong wind during the non-typhoon period were analyzed using, a cluster analysis of the observational data and of special strong wind advisories and, warnings issued by the Korean Meteorological Administration. On the Korean Peninsula, strong winds during non-typhoon periods showed a wide variety of spatial characteristics. In particular, the cluster analysis showed that strong winds could be classified into six clusters on the Korean Peninsula, and that the spatial distribution, occurrence rate of strong winds, and strong wind speed in each cluster were complex and diverse. In addition, our analysis of the frequency of issuance of special strong wind warnings showed a significant difference in the average frequency of strong wind warnings issued in metropolitan cities, with relatively high numbers of warnings issued in Gyeongsangbuk-do and, Jeollanam-do, and low numbers of warning issued inland and in other metropolitan cities. As a result of the changing trend in warnings issued from 2004 to 2019, Ulsan and Busan can be interpreted as having a relatively high number of warnings; the frequency of strong wind warnings issuances and strong wind occurrences in these cities is increasing rapidly. Based on the results of this study, it is necessary to identify areas with similar strong wind characteristics and consider specific regional standards in terms of disaster prevention.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.25 no.5
• /
• pp.291-300
• /
• 2013

Typhoon simulation method is widely used to estimate sea surface wind speeds during the typhoon periods. Holland (1980) model has been regarded to provide relatively better results for observed wind data. JTWC or RSMC best track data are available for typhoon modeling, but these data show slightly different because the data generation process are different. In this paper, a Newton-Raphson method is used to solve the two nonlinear equations based on the Holland model that is formed by the two typhoon parameters, i.e. the longest radius of 25 m/s and 15 m/s wind speeds, respectively. The solution is the radius of maximum wind speed which is of importance for typhoon modeling. This method is based on the typhoon wind profile of JMA and it shows that Holland model appears to fit better the characteristics of typhoons on the temporal and spatial changes than that of the other models. In case of using RSMC best track data, the method suggested in this study shows better and more reasonable results for the estimation of radius of maximum wind speed because the consistency of the input data is assured.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.18 no.2
• /
• pp.4089-4095
• /
• 1976

The safety of shore structure including the sea dipe is largely affected by typhoon. Accordingly it is desirable to analize the typhoon and determine the wind direction and velocity for use in planning and design of the structure. This method was adopted for the design of the Yong San Gang Estuary Dam. A comparative study of the results of typhoon analysis with the meteorological data obtained through actual observation is summarized as follows; (1) 62% of the typhoons occur during May to June in a year, and 62% of the typhoons which have an influence on the Korean peninsula, especially the proposed estuary dam fsite, proceed eastward through the zone in lat. 36$^{\circ}$-37$^{\circ}$N. Such typhoons occur two to three times a year on the average. (2) Data on typhoon "SARL" were used as a model case in designing the estuary dam, where it was proved that a southwesterly wind had a maximum velocity of 30m/sec in case r=150km, ${\alpha}$=120$^{\circ}$. Within the range of 22$^{\circ}$30'on the right and left side of the fetch line of the estuary dam, the wind direction varied SSW\longrightarrowSW\longrightarrowWSW, and the wind velocity varied 29m/sec\longrightarrow30m/sec\longrightarrow125m/sec. Such phenomemum lasted for five hours. (3) An analysis of data obtained during 44 years at Mok Po Meteorological Station shows that a wind with a velocity of some 25m/sec occurred twelve times in the S-direction and two times in the SW-direction, while that with a velocity of 30m/sec occurred three times in the S-direction, three times in the SSW-direction and one time in the SW-direction. The wind which had an influence on the estuary dam had a direction of SSW\longrightarrowSW\longrightarrowWSW and a velocity of min. 30m/sec. Actually, a wind with a max. velocity of 31.3m/sec occurred in the SSW-direction on March 15 and 16, 1956 where the mean velocity during two hours was 28m/sec and that during four hours was 24.6m/sec. (4) The data obtained through actual observation show that when the velocity is low, the wind with a fixed direction lasts long, and when the velocity is high, it is short-lived. It is difficult to determine the velocity of a wind which blows in a fixed direction for consecutive two or four hours. Therefore, the values obtained through typhoon analysis are larger that those obtained through actual observation, and hence, it is resonable to use the analyzed valuse for design of the estuary dam and shore structures. (5) The greatest effect was had on the estuary dam when typhoon was proceeding at a velocity of 29.71m/sec in the direction of ${\alpha}$=120$^{\circ}$(SW) at a point of R=150km from the center of the typhoon.

• Atmosphere
• /
• v.30 no.4
• /
• pp.347-360
• /
• 2020

The automatic algorithm optimized for the Korean Peninsula was developed to detect and track the center of typhoon based on a geometrical method using high-resolution retrieved WISSDOM (WInd Syntheses System using DOppler Measurements) wind and reflectivity data. This algorithm analyzes the center of typhoon by detecting the geometric circular structure of the typhoon's eye in radar reflectivity and vorticity 2D field data. For optimizing the algorithm, the main factors of the algorithm were selected and the optimal thresholds were determined through sensitivity experiments for each factor. The center of typhoon was detected for 5 typhoon cases that approached or landed on Korean Peninsula. The performance was verified by comparing and analyzing from the best track of Korea Meteorological Administration (KMA). The detection rate for vorticity use was 15% higher on average than that for reflectivity use. The detection rate for vorticity use was up to 90% for DIANMU case in 2010. The difference between the detected locations and best tracks of KMA was 0.2° on average when using reflectivity and vorticity. After the optimization, the detection rate was improved overall, especially the detection rate more increased when using reflectivity than using vorticity. And the difference of location was reduced to 0.18° on average, increasing the accuracy.

• Journal of the Korean earth science society
• /
• v.40 no.5
• /
• pp.502-517
• /
• 2019

Global warming and rapid climate change have long affected the characteristics of typhoons in the Northwest Pacific, which has induced increasing devastating disasters along the coastal regions of the Korean peninsula. Synthetic Aperature Radar (SAR), as one of the microwave sensors, makes it possible to produce high-resolution sea surface wind field around the typhoon under cloudy atmospheric conditions, which has been impossible to obtain the winds from satellite optical and infrared sensors. The Geophysical Model Functions (GMFs) for sea surface wind retrieval from SAR data requires the input of wind direction, which should be based on the accurate estimation of the center of the typhoon. This study estimated the typhoon centers using Sentinel-1A images to improve the problem of typhoon center detection method and to reflect it in retrieving the sea surface wind. The results were validated by comparing with the typhoon best track data provided by the Korea Meteorological Administration (KMA) and Japan Meteorological Agency (JMA), and also by using infrared images of Himawari-8 satellite. The initial center position of the typhoon was determined by using VH polarization, thereby reducing the possibility of error. The detected center showed a difference of 23.76 km on average with the best track data of the four typhoons provided by the KMA and JMA. Compared to the typhoon center estimated by Himawari-8 satellite, the results showed an average spatial variation of 11.80 km except one typhoon located near land with a large difference of 58.73 km. This result suggests that high-resolution SAR images can be used to estimate the center and retrieve sea surface wind around typhoons.

• Atmosphere
• /
• v.24 no.3
• /
• pp.419-432
• /
• 2014

An assessment of typhoon intensity predictability of numerical models was conducted to develop the typhoon intensity forecast guidance comparing with the RSMC-Tokyo best track data. Root mean square error, box plot analysis and time series of wind speed comparison were performed to evaluate the each model error level. One of noticeable fact is that all models have a trend of error increase as typhoon becomes stronger and the Global Forecast System showed the best performance among the models. In the detailed analysis in two typhoon cases [Danas (1324) and Haiyan (1330)], GFS showed good performance in maximum wind speed and intensity trend in the best track, however it could not simulate well the rapid intensity increasing period. On the other hand, ECMWF and Hurricane-WRF overestimated the typhoon intensity but simulated track trend well.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.29 no.7
• /
• pp.770-778
• /
• 2023

Sea surface wind is an important variable for elucidating the atmospheric-ocean interactions and predicting the dangerous weather conditions caused by oceans. Accurate sea surface wind data are required for making correct predictions; however, there are limited observational datasets for oceans. Therefore, this study aimed to obtain long-period high-resolution sea surface wind data. First, the ERA5 reanalysis wind field, which can be used for a long period at a high resolution, was regridded and synthesized using the asymmetric typhoon wind field calculated via the Generalized Asymmetric Holland Model of the numerical model named ADvanced CIRCulation model. The accuracy of the asymmetric typhoon synthesized wind field was evaluated using data obtained from Korea Meteorological Administration and Japan Meteorological Administration. As a result of the evaluation, it was found that the asymmetric typhoon synthetic wind field reproduce observations relatively well, compared with ERA5 reanalysis wind field and symmetric typhoon synthetic wind field calculated by the Holland model. The sea surface wind data produced in this study are expected to be useful for obtaining storm surge data and conducting frequency analysis of storm surges and sea surface winds in the future.

• Journal of Environmental Science International
• /
• v.24 no.12
• /
• pp.1657-1671
• /
• 2015

In this study, the wind direction and the wind speed of the nearest temperature observations point of the National Weather Service was analyzed in order to investigate the rapid rise and drop of water temperature in the East Coast appeared after passing of the 2015 typhoon No. 9 and 11. Then the figures were simulated and analyzed using the WRF(weather research and forecast) model to investigate in more detailed path of the typhoon as well as the changes in the wind field. The results were as follows. A sudden drop of water temperature was confirmed due to upwelling on the East coast when ninth typhoon Chanhom is transformed from tropical cyclones into extra tropical cyclone, then kept moving eastwards from Pyongyang forming a strong southerly wind after 13th and this phenomenon lasted for two days. The high SST(sea surface temperature) is confirmed due to a strong northerly wind by 11th typhoon Nangka. This strong wind directly affected the east coast for three days causing the Ekman effect which transported high offshore surface waters to the coast. The downwelling occurred causing an accumulation of high temperature surface water. As a results, the SST of 15m and 25m rose to that of 5m.

• Wind and Structures
• /
• v.10 no.6
• /
• pp.543-554
• /
• 2007

The suspension bridge is situated in an area of complex topography with both open sea and overland turbulence characteristics, and it is subject to frequent typhoon occurrences. This paper investigates experimentally the possible vortex shedding events of the structure under high wind and typhoon conditions. A single-degree-of-freedom model for the vibration of a unit bridge deck section is adopted to determine the amplitude of vibration and to estimate the parameters related to the lifting force in a vortex shedding event. The results of the studies are presented in a companion paper (Law, et al. 2007). In this paper, statistical analysis on the measured responses of the bridge deck shows that the vibration response at the first torsional mode of the structure has a significant increase at and beyond the critical wind speed for vortex shedding as noted in the wind tunnel tests on a section model of the structure.