• Journal of the Korea Society of Computer and Information
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• v.28 no.11
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• pp.13-20
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• 2023

In this paper, we propose a water temperature prediction method using feature extraction and reconstructed data based on LSTM-Autoencoder. We used multivariate time series data such as sea surface water temperature in the Naksan area of the East Sea where the cold water zone phenomenon occurred, and wind direction and wind speed that affect water temperature. Using the LSTM-Autoencoder model, we used three types of data: feature data extracted through dimensionality reduction of the original data combined with multivariate data of the original data, reconstructed data, and original data. The three types of data were trained by the LSTM model to predict sea surface water temperature and evaluated the accuracy. As a result, the sea surface water temperature prediction accuracy using feature extraction of LSTM-Autoencoder confirmed the best performance with MAE 0.3652, RMSE 0.5604, MAPE 3.309%. The result of this study are expected to be able to prevent damage from natural disasters by improving the prediction accuracy of sea surface temperature changes rapidly such as the cold water zone.

• Journal of the Institute of Convergence Signal Processing
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• v.22 no.4
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• pp.164-170
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• 2021

Research was conducted to analyze and improve the kinetic performance of offshore wind power generators. The shape used in this study was taken with reference to the previous paper, and the size of the repair area was designed at 80%, 60%, 40%, and 20%, respectively, and the exercise performance was confirmed accordingly. The sea state was calculated in Sea State 4, 5, and 6. In the calculation process, the calculation was performed using commercial computational hydrodynamics (ANSYS) and AQUA. In the case of overall exercise performance, it was confirmed that the smaller the size of the repair area, the smaller the exercise such as heave, roll, and pitch. However, it was confirmed that in the case of a shape in which the size of the repair area was rapidly reduced, there may be cases in which the restoration performance was not satisfied when the restoration calculation was performed. In addition, it was confirmed that there may be an appropriate repair surface depending on the sea condition.

• Proceedings of the KSRS Conference
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• v.2
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• pp.997-1000
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• 2006

We estimate the net heat flux in the tropical and subtropical Atlantic Ocean using satellite data. These fluxes are related to changes in sea surface temperature (SST). This variable influences atmospheric circulations and is indicative of surface and subsurface oceanic circulations. We employ data from the geostationary METEOSAT-7 and 8 satellites and from the Special Sensor Microwave/Imager (SSM/I) for the shortwave and long-wave radiative fluxes, and for estimates of SST. For turbulent flux calculations, we use the bulk aerodynamic method with satellite estimates for wind speed and atmospheric humidity and temperature.

• Atmosphere
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• v.18 no.3
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• pp.171-182
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• 2008

In this study, we analyzed the spatial and temporal distribution of wind resources over Korea based on hourly observational data recorded over a period of 5 years from 457 stations belonging to Korea Meteorological Administration (KMA). The surface and 850 hPa wind data obtained from the Korea Local Analysis and Prediction System (KLAPS) and the Regional Data Assimilation and Prediction System (RDAPS) over a period of 1 year are used as supplementary data sources. Wind speed is generally high over seashores, mountains, and islands. In 62 (13.5%) stations, mean wind speeds for 5 years are greater than $3ms^{-1}$. The effects of seasonal wind, land-sea breeze, and mountain-valley winds on wind resources over Korea are evaluated as follows: First, wind is weak during summer, particularly over the Sobaek Mountains. However, over the coastal region of the Gyeongnam-province, strong southwesterly winds are observed during summer owing to monsoon currents. Second, the wind speed decreases during night-time, particularly over the west coast, where the direction of the land breeze is opposite to that of the large-scale westerlies. Third, winds are not always strong over seashores and highly elevated areas. The wind speed is weaker over the seashore of the Gyeonggi-province than over the other seashores. High wind speed has been observed only at 5 stations out of the 22 high-altitude stations. Detailed information on the wind resources conditions at the 21 stations (15 inland stations and 6 island stations) with high wind speed in Korea, such as the mean wind speed, frequency of wind speed available (WSA) for electricity generation, shape and scale parameters of Weibull distribution, constancy of wind direction, and wind power density (WPD), have also been provided. Among total stations in Korea, the best possible wind resources for electricity generation are available at Gosan in Jeju Island (mean wind speed: $7.77ms^{-1}$, WSA: 92.6%, WPD: $683.9Wm^{-2}$) and at Mt. Gudeok in Busan (mean wind speed: $5.66ms^{-1}$, WSA: 91.0%, WPD: $215.7Wm^{-2}$).

• Fisheries and Aquatic Sciences
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• v.24 no.7
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• pp.243-259
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• 2021

The spatial and temporal behaviors and fluctuations of the cold water that appeared in the South East Sea and the East Sea coast from 2016 to 2017 were investigated. The water temperature drop was large in the east coast from April to June and the southeast coast from July to September, and the temperature drop period was longer in the southeast coast. The water temperature fluctuated sensitively to the wind direction, and it gradually decreased in the southwest wind but rose as if jumping in the northeast wind. Wind stress and surface water temperature had an inverse correlation, which was larger in Bukhang-Idukseo, and decreased toward the north of Guryongpo. The cold water appeared mainly in Geojedo-Pohang after 1 to 2 days when the southwest wind was strong, but when the wind became weak, it shrank to the Idukseo (Ulgi-Gampo) and extended into the open sea in a tongue shape. Cold water was distributed only in Samcheok-Toseong in mid-May, Idukseo-Guryongpo and Hupo-Jukbyeon-Samcheok from late May to mid-July, and Bukhang-Idukseo in August-September. The intensity of cold water was greatest in mid-August, and the center of cold water descended from the east coast to the southeast coast from spring to summer. The water temperature fluctuation was dominant at the periods of 1 d and 7-21 d. In wavelet spectrum analysis of water temperature and wind, wind speed increase-water temperature decrease showed phase difference of 12 h in 2 d, 18 h in 3 d, 1.5 d in 4-8 d, and 2-3 d in 8-24 d period. The correlation between the two parameters was large in Geojedo and Namhang, Bukhang-Idukseo, Guryongpo-Jukbyeon, and Samcheok-Toseong. Monitoring stations with high correlation in all periods were generally parallel to the monsoon direction.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.615-620
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• 2002

Probability distribution of the sea surface slope is estimated using sun glitter images derived from visible radiometer on Geostationary Meteorological Satellite (GMS) and surface vector winds observed by spaceborne scatterometers. The brightness of the visible images is converted to the probability of wave surfaces which reflect the sunlight toward GMS in grids of 0.25 deg $\times$ 0.25 deg. Slope and azimuth angle required for the reflection of the sun's ray toward GMS are calculated for each grid from the geometry of GMS observation and location of the sun. The GMS images are then collocated with surface wind data observed by three scatterometers. Using the collocated data set of about 30 million points obtained in a period of 4 years from 1995 to 1999, probability distribution function of the surface slope is estimated as a function of wind speed and azimuth angle relative to the wind direction. Results are compared with those of Cox and Munk (1954a, b). Surface slope estimated by the present method shows narrower distribution and much less directivity relative to the wind direction than that reported by Cox and Munk. It is expected that their data were obtained under conditions of growing wind waves. In general, wind waves are not always developing, and slope distribution might differ from the results of Cox and Munk. Most of our data are obtained in the subtropical seas under clear-sky conditions. This difference of the conditions may be the reason for the difference of slope distribution.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.05b
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• pp.121-122
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• 2003

Deposition to the sea surface is one of ozone's principal loss mechanisms (Galbally and Roy, 1980; Levy et al., 1985; Kramm, 1995). However, since complicated physical and chemical processes are involved, large uncertainties remain in evaluating this loss mechanism that need to be better characterized. In this study we attempted to explore possible causes that give rise to large variability of ozone deposition velocity in terms of wind speed and chemical reactivity in the aqueous-phase film. (omitted)

• Atmosphere
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• v.20 no.3
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• pp.343-353
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• 2010

A regional wind network with complex surface conditions must be designed with sufficient space and time resolution to resolve the local circulations. In this study, the spatial variations of the wind field observed in the Seoul and Jeju regional networks were evaluated in terms of annual, seasons, and months to assess the spatial homogeneity of wind fields within the regional networks. The coherency of the wind field as a function of separation distance between stations indicated that significant coherency was sometimes not captured by the network, as inferred by low correlations between adjacent stations. A meso-velocity scale was defined in terms of the spatial variability of the wind within the network. This problem is predictably most significant with weak winds, dull prevailing wind, clear skies and significant topography. The relatively small correlations between stations imply that the wind at a given point cannot be estimated by interpolating winds from the nearest stations. For the Seoul and Jeju regional network, the meso-velocity scale has typically a same order of magnitude as the speed of the network averaged wind, revealing the large spatial variability of the Jeju network station imply topography and weather. Significant scatter in the relationship between spatial variability of the wind field and the wind speed is thought to be related to thermally-generated flows. The magnitude of the mesovelocity scale was significantly different along separation distance between stations, wind speed, intensity of prevailing wind, clear and cloudy conditions, topography. Resultant wind vectors indicate much different flow patterns along condition of contributing factors. As a result, the careful considerations on contributing factors such as prevailing wind in season, weather, and complex surface conditions with topography and land/sea contrast are required to assess the spatial variations of wind field on a regional network. The results in the spatial variation from the mesovelocity scale are useful to represent the characteristics of regional wind speed including lower surface conditions over the grid scale of large scale atmospheric model.

• Journal of Fisheries and Marine Sciences Education
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• v.17 no.2
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• pp.209-217
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• 2005

The energy balance of the surface layer of the water (the Yellow Sea, the East China Sea and the East Sea) was examined using satellite data. Variations of the net heat flux were similar to those of the latent heat flux which was more intensive than the sensible heat flux. The sensible heat flux was affected the difference between the sea surface temperature and the air temperature and was less important over the Yellow Sea. The maximum of the latent heat flux occurred in autumn when the air is drier and the wind is stronger. The shortwave radiation flux decreased with the latitude and depended on the cloudiness as the longwave radiation flux does. Annual variations of heat fluxes show that the latent heat flux was more intensive over the East China Sea than the East Sea and the Yellow Sea, while the spatial differences of the other heat fluxes were weak.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.9
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• pp.969-975
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• 2013

As energy shortage is getting more serious, wind energy source is more promoted around the world. Blade is a key component of wind turbine. Local breakages and/or contamination in the blade bring degradation in aerodynamic efficiency and life-time. However, it is not easy and even dangerous for human workers to access the blade for inspection and maintenance since its size is huge and located at high mountains and rough sea, which are windy places. This paper deals with a novel moving mechanism that efficiently carries human workers or robots to the wind turbine blade. The proposed mechanism utilizes flexible tube with pressurized air that rolls and climbs over the blade surface. So, the tube naturally adapts the changing surface of the blade and acts no harm to it. This paper discusses about its concept, detail design, and advantages. The feasibility of the proposed mechanism is proved through experiments prototype.