• Ocean and Polar Research
• /
• v.31 no.4
• /
• pp.297-304
• /
• 2009

We investigated the response of the westerly winds over the Southern Ocean (SO) to glacial boundary conditions for the Last Glacial Maximum using the CCM3 atmospheric general circulation model. In response to glacial boundary conditions, the zonally averaged maximum SO westerly winds weakened 20-35% and were displaced toward the equator by 3-4 degrees. This weakening of the SO westerly winds arose from a substantial increase in mean sea level pressure (MSLP) in the southern part of the SO around Antarctica relative to the northern part. The increase in MSLP around Antarctica is associated with a marked temperature reduction caused by an increase in sea ice cover and ice albedo feedback during the glacial time. The weakened westerly winds in the SO and their equator-ward displacement might play a role in reducing the atmospheric $CO_2$ concentration by reducing upwelling of the carbon rich deep water during the glacial time.

• Journal of the Korean earth science society
• /
• v.38 no.1
• /
• pp.24-34
• /
• 2017

The westerly waves generation is described in the advanced earth science textbook used at high school as follows: as westerly wind approaches and blows over large mountains, the air flow shows wave motions in downwind side, which can be explained by the conservation of potential vorticity. However, there has been no case study showing the phenomena of the mesoscale westerly waves with observational data in the area of small mountains in Korea. And thus the wind speed and time persistency of westerly winds along with the width and length of mountains have never been studied to explain the generation of the westerly waves. As a first step, we assured the westerly waves generated in the downwind side of Sobaek mountains based on surface station wind data nearby. Furthermore, the critical or minimum wind velocity of the westerly wind over Sobaek mountains to generate the downwind wave were derived and calcuated tobe about $0.6m\;s^{-1}$ for Sobaek mountains, which means that the westerly waves could be generated in most cases of westerly blowing over the mountains. Using surface station data and 4-dimensional assimilation data of RDAPS (Regional Data Assimilation and Prediction System) provided by Korea Meteorological Agency, we also analyzed cases of westerly waves occurrence and life cycle in the downwind side of Sobaek mountains for a year of 2014. The westerly waves occurred in meso-${\beta}$ or -${\gamma}$ scales. The westerly waves generated by the mountains disappeared gradually with wind speed decreasing. The occurrence frequency of the vorticity with meso-${\beta}$ scale got to be higher when the stronger westerly wind blew. When we extended the spatial range of the analysis, phenomena of westerly waves were also observed in the downwind side of Yensan mountains in Northeastern China. Our current work will be a study material to help students understand the atmospheric phenomena perturbed by mountains.

• Journal of Environmental Health Sciences
• /
• v.16 no.2
• /
• pp.21-29
• /
• 1990

This study investigated to find out the patterns of the wind direction and wind speeds influenced by concentration of sulfur dioxide in Taegu area for a year in 1988.The results were as follows: Prevailing wind by months where easterly wind from May to September and the other months were westerly and / or west-north-westerly wind. Condition of calm was the most at December(8.6%). Prevailing wind by seasons were westerly and easterly wind in spring and autumn, east-north-easterly and/or west-south wind in summer, the other hand, west-south-westerly and/or west-north-westerly wind in winter. Mean concentration of sulfur dioxide (SO$_{2}$) at each sites were influenced by prevailing wind and location of industrial estates. Mean wind speeds by times were the highest at the before and after 4 P.M.,but the lowest at the before and after 5 A.M. Average wind velocity were highest at Spring (3.38m / sec).

• Journal of the Korean earth science society
• /
• v.27 no.2
• /
• pp.177-187
• /
• 2006

Due to a lack of reproducibility and visibility of the conventional equipment for westerly wave simulation, it is difficult to have indoor experiments at high school that show the stream of Hadley cell. A modified improvement of the old one improves the problem. The side wall and bottom of the new equipment is made by copper and acrylic resin, respectively, in order to clarify the difference between the water temperature inside and outside of the water tank. The equipment also has a high quality digital record for generating exact analysis of the results. And we also carried out several experiments that relate theoretical and experimental aspection of westerly wave. Temperature Detected Sheet (TDS) in flow visualization unit provides not only visual information of liquid flow, but also clear understanding of the relation between upper and lower wind flow structure. And the liquid stream simulated in indoor experiment using proposed equipment is commensurate with westerly wave in real atmosphere. The efficiency of educational properties of the proposed equipment is verified indirectly by Likert Scales survey of high school teachers.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
• /
• v.10 no.S_1
• /
• pp.29-33
• /
• 2001

A numerical simulation was carried out to investigate the mechanism of snowfall around the Seoul region during a cold air-outbreak in the winter season. A particular case was selected for this study(Dec. 19, 1999). The inflow directions of the synoptic flow in the upper and lower levels were westerly and north-westerly, respectively. Plus, there was a deep trough and thermal ridge at a level of 500/700/850 hPa over the Bal-Hae region, in the northern part of the Korean peninsula. According to the model results, snowfall occurred around the Seoul region with the simultaneous existence of a strong static instability in the lower atmosphere, northerly or westerly dry air advection, and strong thermal advection toward the Seoul region. There was a strong convergence thereby indicating the existence of convective rolls in the clouds. The main energy source of convection over the Yellow sea was a sensible heat flux. The main moisture source was convection. Radiative cooling in the cloud layer intensified the static instability in the lower atmosphere.

• Korean Journal of Remote Sensing
• /
• v.31 no.2
• /
• pp.65-75
• /
• 2015

In this study, the observation environment of surface wind at an automatic weather station (AWS 288) located at Naei-dong, Mirang-si was analyzed using a computational fluid dynamics (CFD) model and geographic information system (GIS). The 16 cases with different inflow directions were considered before and after construction of an apartment complex around the AWS 288. For three inflow directions (south-south-westerly, south-south-easterly, and north-north-westerly), flow characteristics around the AWS 288 were investigated in detail, focusing on the changes in wind speed and direction at the AWS location. There was marked difference in wind speed between before and after construction of the apartment complex in the south-south-westerly case. In the south-south-easterly and north-north-westerly cases which were frequently observed at the AWS 288, the construction of the apartment complex had no marked influence on the observation of surface wind.

• Ocean and Polar Research
• /
• v.24 no.2
• /
• pp.135-146
• /
• 2002

The upper ocean in the western equatorial Pacific warm pool during TOGA-COARE IMET IOP was simulated using a one-dimensional turbulence closure ocean mixed-layer model, which considered recent observations, such as the remarkable enhancement of turbulent kinetic energy near the ocean surface. The shoaling/deepening of the mixed layer and warming/cooling subsurface water in the model were in reasonable agreement with the observations. There was a significant improvement in simulating the cooling trend of the sea surface temperature under a westerly wind burst with heavy rainfall over previous simulations using bulk mixed-layer models. By contrast the simulated sea surface salinity (SSS) departed significantly from the observed SSS, especially during a westerly burst and the subsequent restratification period, which might be due to 3-D control processes, such as downwelling/upwelling or advection.

• Journal of Environmental Science International
• /
• v.25 no.7
• /
• pp.1017-1028
• /
• 2016

Wind information is one of the major inputs for the prediction of urban air flow using computational fluid dynamic (CFD) models. Therefore, the numerical characteristics of the wind data formed at their mother domains should be clarified to predict the urban air flow more precisely. In this study, the formation characteristics of the wind data in the Seoul region were used as the inlet wind information for a CFD based simulation and were analyzed using numerical weather prediction models for weather research and forecasting (WRF). Because air flow over the central part of the Korean peninsula is often controlled not only by synoptic scale westerly winds but also by the westerly sea breeze induced from the Yellow Sea, the westerly wind often dominates the entire Seoul region. Although simulations of wind speed and air temperature gave results that were slightly high and low, respectively, their temporal variation patterns agreed well with the observations. In the analysis of the vertical cross section, the variation of wind speed along the western boundary of Seoul is simpler in a large domain with the highest horizontal resolution as compared to a small domain with the same resolution. A strong convergence of the sea breeze due to precise topography leads to the simplification of the wind pattern. The same tendency was shown in the average vertical profiles of the wind speed. The difference in the simulated wind pattern of two different domains is greater during the night than in the daytime because of atmospheric stability and topographically induced mesoscale forcing.

• Journal of Environmental Science International
• /
• v.14 no.1
• /
• pp.41-51
• /
• 2005

Using three-dimensional non-hydrostatical numerical model with one way double nesting technique, atmo­spheric circulation in the mountainous coastal region in summer was investigated from August 13 through 15, 1995. During the day, synoptic westerly wind blows over Mt. Mishrung in the west of a coastal city, Sokcho toward the East Sea, while simultaneously, easterly upslope wind combined with both valley wind from plain (coast) toward mountain and sea-breeze from sea toward inland coast blows toward the top of the mountain. Two different directional wind systems confront each other in the mid of eastern slope of the mountain and the upslope wind goes up to the height over 2 km, becoming an easterly return flow in the upper level over the sea and making sea-breeze front with two kinds of sea-breeze circulations of a small one in the coast and a large one in the open sea. Convective boundary layer is developed with a thickness of about 1km over the ground in the upwind side of the mountain in the west and a thickness of thermal internal boundary layer from the coast along the eastern slope of the mountain is only confined to less than 200 m. On the other hand, after sunset, no prohibition of upslope wind generated during the day and downward wind combined with mountain wind from mountain towardplain and land-breeze from land toward under nocturnal radiative cooling of the ground surfaces should intensify westerly downslope wind, resulting in the formation of wind storm. As the wind storm moving down along the eastern slop causes the development of internal gravity waves with hydraulic jump motion in the coast, bounding up toward the upper level of the coastal sea, atmospheric circulation with both onshore and offshore winds like sea-breeze circulation forms in the coastal sea within 70 km until midnight and after that, westerly wind prevails in the coast and open seas.

• Journal of Environmental Science International
• /
• v.5 no.2
• /
• pp.131-140
• /
• 1996

Analysis of hourly variations of sulfur dioxide ($SO_2$) concentrations affected by regional climates for the period of yellow sandy dusts was carried out from March 31 through April 9, 1993. The concentration of 50, at a coastal city, Kangnung city, was much higher than that at an inland city Wonju in the west, but the hourly distrbutions of $SO_2$ concentrations show a similar tendency at both cities. Under the prevailing synoptic-scale westerly winds blowing over a high Mt. Taegualyang in the west toward Kangnung city in the eastern coastal region, the $SO_2$ at Kangnung is trapped by an easterly sea-breeze during the day and under prevailing easterly winds, it is also isolated by the high wall of Mt. Taegualyang, with its high concentration from 14 to 16 LST. Furthermore, when the westerly winds were dominent all day long the high $SO_2$ concentrations at Kangnung were produced by its intrusion from a urban city, Wonju or China in the west into a mountainous coastal city, Kangnung, to some extent, and when the air becomes rapidly cooled down at the clear daytime or the nighttime, their concentrations are also increased by a great amount of heating fuel combustion. Especilly, its maximum concentrations were shown in Wonju and Kangnung from 08 LST through 10 LST, due to the increase of auto vehicles near the beginning time of office hour and were detected again after sunset due to both increases of vehicles at the end of office hour and heating fuel combustion. During the period of Yellow Sandy Dusts which are transported from China into Korea, the $SO_2$ concentrations on rainy days at Wonju and Kangnung were much lower than the monthly mean values of $SO_2$, and their low concentrations could be caused by the scavenging process of rain.