• Journal of Environmental Science International
• /
• v.11 no.4
• /
• pp.289-295
• /
• 2002

We would like to investigate the strong wind phenomenon effecting to the onset of a sea breeze. It is general the fact that the onset time of a sea breeze is mainly affected according to the distance from the coastline but we find the reversal fact. The onset time at Suyoung is faster than that at Haeundae in spite of the observation site of Suyoung is 5 m and that of Haeundae is 1 km away from the coastline. This is the reason that the nighttime air is converged the lower area by surface cooling and then it is strongly drained onto the lowest area, Suyoung river until the sunrise. it is proved by observation data at Suyoung and Haeundae.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.31 no.3
• /
• pp.93-102
• /
• 2023

Jeju International Airport is characterized by the occurrence of low-level windshear due to its location, surrounding terrain, and its weather characteristics. Especially the low-level windshear accompanied by tailwinds on both sides of the runway i.e., bidirectional tailwind, is a hazardous weather phenomenon with unique characteristics that are difficult to find at any other airports. This study focuses on bidirectional tailwind occurrence at Jeju International Airport in 2020-2021. As a result, characteristic pressure patterns of the types that cause bidirectional tailwind was identified as it was possible to categorize strong wind types such as 1) strong southwest wind, 2) strong east wind, and 3) strong northwest wind, which do not cause bidirectional tailwind, and wind direction variation types such as 4) bidirectional tailwind, and 5) south wind followed by southwest wind, which cause bidirectional tailwind. The results of this study are expected to contribute to improving aviation safety by enabling aviation operators to predict and take appropriate safety measures based on their understanding of the causes and characteristics of bidirectional tailwind.

• Journal of Korean Society for Atmospheric Environment
• /
• v.16 no.5
• /
• pp.487-497
• /
• 2000

Spring time is a favorable season to be easily observed the Yellow Sand phenomenon in East Asia. In particular most of the phenomenon tend to occur in April. However, Yellow Sand phenomenon was observed from almost the whole country of Korea in winter of 1966, 1977 and 1999. The features of the synoptic weather pattern in the source regions, air stream flow between the source region and Korea, the measurement of TSP concentration, aerosol size distribution, and chemical composition of snow samples associated with Yellow Sand phenomenon were investigated. The result showed the characteristic evolutionary feature of the synoptic system associated with Yellow Sand phenomena, that is, a strong low level wind mobilized the dust within 2 or 3 days before Yellow Sand phenomenon being observed in Seoul. The wind was remarkably intensified in the source region on January 24, 1999 under the strong pressure gradient, A trajectory analysis showed that the Yellow Sand particle could be reached to Korea within 2 days from the source region, Gobi desert, through Loess plateau and Loess deposition region. The TSP concentration at the top of Kwanak mountain during the Yellow Sand phenomenon is abruptly increasing than the monthly mean concentration. The size resolved number concentration of aerosols ranging from 0.3 to 25${\mu}{\textrm}{m}$ was analyzed during Yellow Sand episode. It was evident that aerosols were distinguished by particles in the range of 2-3 ${\mu}{\textrm}{m}$ to result in the abrupt increase in January 1999, After Yellow Sand phenomenon, there was heavy snow in Seoul. By the analysis of snow collected during that time, it was observed that both the Ca(sup)2+ concentration and pH were increased abnormally compared to those in the other winter season.

• Wind and Structures
• /
• v.35 no.4
• /
• pp.255-268
• /
• 2022

Light-weight or low-damped structures may encounter the unsteady galloping instability that occurs at low reduced wind speeds, where the classical quasi-steady assumption is invalid. Although this unsteady phenomenon has been widely studied for rectangular cross sections with one side perpendicular to the incidence flow, the effect of the mean wind angle of attack has not been paid enough attention yet. With four sectional models of different side ratios and geometric shapes, the presented research focuses on the effect of the wind angle of attack on unsteady galloping instability. In static tests, comparatively strong vortex shedding force was noticed in the middle of the range of flow incidence where the lift coefficient shows a negative slope. In aeroelastic tests with a low Scruton number, the typical unsteady galloping, which is due to an interaction with vortex-induced vibration and results in unrestricted oscillation initiating at the Kármán vortex resonance wind speed, was observed for the wind angles of attack that characterize relatively strong vortex shedding force. In contrast, for the wind angles of attack with relatively weak shedding force, an "atypical" unsteady galloping was found to occur at a reduced wind speed clearly higher than the Kármán-vortex resonance one. These observations are valid for all four wind tunnel models. One of the wind tunnel models (with a bridge deck cross section) was also tested in a turbulent flow with an intensity about 9%, showing only the atypical unsteady galloping. However, the wind angle of attack with the comparatively strong vortex shedding force remains the most unfavorable one with respect to the instability threshold in low Scruton number conditions.

• Journal of the Korean earth science society
• /
• v.24 no.4
• /
• pp.325-336
• /
• 2003

The onset time of sea breeze at Haeundae is faster than that at Suyoung in spite of the observation site at Suyoung being 5m and that of Haeundae being 1 km away from the coastline. We therefore simulate the effects of terrain on the onset time of sea breeze at Suyoung and Haeundae districts by using the LCM(Local Circulation Model). This phenomenon is due to the nighttime density flow, which is created by nighttime radiative cooling. It follows the slope of the highlands surrounding the urban area, gathers at a central area of Busan, and then flows out to a lower area like Suyoung river. This process continues after sunrise. In researching the AWS wind speed, we find an important thing. That is to say, the nighttime mean wind speed at Suyoung is three times greater than that at Haeundae. This property shows that Suyoung is an outflow channel of nighttime air mass. The above observed data shows that terrain effect has a important role on the onset of sea breeze.

• Journal of Environmental Science International
• /
• v.7 no.3
• /
• pp.291-300
• /
• 1998

Recently, upwelling of anoxic bottom water mass have been frequently observed in northeast part of Tokyo Bay in Japan during summer to autumn. Since the colour of water surface becomes milkyblue or milkygeen, the upwelling phenomenon Is called 'Blue Tide'. The data analysis of field surveys during 'Blue Tide' appearance have been performed for understanding the physical features of the 'Blue Tide' phenomena In Tokyo Bay. It becomes clear that (1) the formation of the anoxic bottom water correlates well with the temperature difference between the surface and bottom waters, (21 there are two necessary conditions for generating 'Blue Tide': that Is, strong stratincation and off-shore wind. The strong southwest(on-shored wand before the 'Blue Tide' appearance may play an iniportant role to make the striancation strengthen. When these conditions are larger and the northeast or east-northeast (off-shored wind stronger than S ifs blows In succession, the 'Blue Tide' upwelling appears at the head of Tokyo Bay.

• 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.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.29 no.1
• /
• pp.1-8
• /
• 2021

Low level wind shear, which often occurs at Jeju International Airport, is a phenomenon that occurs when the topological location and topographical characteristics of Jeju Island are combined with weather characteristics. Low level wind shears, which are caused by rapid changes in wind direction and wind speed, pose a threat to aircraft safety and also cause abnormal situations, such as aircraft go-around, diversion, and cancellation. Many meteorological studies have been conducted on weather patterns, occurrence periods and frequency of low level wind shears. However, researches related to aircraft operations are limited where here we study the similarities and differences between strong southwest winds and bidirectional tailwind type low level wind shears based on aircraft go-around cases at Jeju International Airport. The results are expected to be used to enhance safety when operating to Jeju International Airport, which includes pilot training that reflects the characteristics generated by wind changes, pilot prior notification, providing pilots with latest trends, and increasing extra fuel.

• 한국전산유체공학회:학술대회논문집
• /
• 2005.04a
• /
• pp.104-108
• /
• 2005

The Korean high speed train runs at 300 km/h, ballast-flying phenomenon often happens by strong train-wind. It is important to consider the prevention of ballast-flying phenomenon, because the train under-body and fares or walker around a rail might be damaged. In this study, Numerical analysis of the flow field of under-body of train and study of heighter-effect were conducted to decrease the speed of under-body. The shape of under-body was simplified for convenience of meshing and analysis. According to results of Taguchi's design by orthogonal arrays, a height of tie is dominant in the flow field, so if the heighter is installed on tie, the speed of under-body might be decreased. The result of this study is useful to build a new high-speed-line.

• Proceedings of the KSR Conference
• /
• 2004.10a
• /
• pp.874-879
• /
• 2004

The Korean high speed train runs at 300 km/h, ballast-flying phenomenon often happens by strong train-wind. It is important to consider the prevention of ballast-flying phenomenon, because the train under-body and fares or walker around a track might be damaged. In this study, Numerical analysis of the under-body flow field of a train and study of heighter-effect were conducted to decrease the speed of under-body. The shape of under-body was simplified for convenience of meshing and analysis. According to results of Taguchi's design by orthogonal arrays, a height of tie is dominant in the flow field, so if the heighter is installed on tie, the speed of under-body might be decreased. To apply the result of this study is useful to build a new high-speed-line might be expected.