• Wind and Structures
• /
• 제5권2_3_4호
• /
• pp.115-126
• /
• 2002

A mesoscale meteorological model is applied to simulate turbulent airflow and eddy shedding over the Isle of Arran, SW Scotland, UK. Under conditions of NW flow, the mountain ridge of Kintyre, located upwind of Arran, induces gravity waves that also affect the airflow over the island. The possibility to nest domains allows description of the airflow over Arran with a very high resolution grid, while also including the effects of the surrounding mainland of Scotland, in particular of the mountain ridge of Kintyre. Initialised with a stably stratified NW flow, the mesoscale model simulates quasi-stationary gravity waves over the island induced by Kintyre. Embedded in the larger scale wave trains there is continuous development of small-scale transient eddies, created at the Arran hill tops, that move downstream through the stationary wave field. Although the transient eddies are more frequently simulated on the northern island where the terrain is more pronounced, they are also produced over Tighvein, a hill of 458 m on the southern island where measurements of surface pressure and 2 m meteorological variables have been recorded at intermittent intervals between 1996 and 2000. Comparison between early observations and simulations so far show qualitatively good agreement. Overall the computations demonstrate that turbulent flow can be modelled with a horizontal resolution of 70 m, and describe turbulent eddy structure on wavelength of only a few hundred metres.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2008년도 International Symposium on Remote Sensing
• /
• pp.297-300
• /
• 2008

High-resolution mesoscale meteorological modeling requires more accurate and higher resolution digital elevation model (DEM) data. Shuttle Radar Topographic Mission (SRTM) has created 90 m DEM for entire globe and that is freely available for meteorological modeling and environmental applications. In this research, the effects of the topographic interpolation methods on high-resolution wind field simulation in the coastal regions were quantitatively analyzed using Weather Research and Forecasting (WRF) model with SRTM data. Sensitivity experiments with three different interpolation schemes (four-point bilinear, sixteen-point overlapping parabolic and nearest neighbor interpolation methods) were preformed using SRTM. In WRF modeling with sixteen-point overlapping parabolic interpolation, the coastal line and some small islands show more clearly than other cases. The maximum height of inland is around 140 meters higher, while the minimum of sea height is about 80 meter lower. As it concerns the results of each scheme it seems that the sixteen-point overlapping parabolic scheme indicates the well agreement with observed surface wind data. Consequently, topographic changes due to interpolation methods can lead to the significant influence on mesoscale wind field simulation of WRF modeling.

• 대기
• /
• 제17권4호
• /
• pp.327-337
• /
• 2007

In this study, we examined the new ensemble training approach to reduce the systematic error and improve prediction skill of wind by using the Short-range Ensemble prediction system (SENSE), which is the mesoscale multi-model ensemble prediction system. The SENSE has 16 ensemble members based on the MM5, WRF ARW, and WRF NMM. We evaluated the skill of surface wind prediction compared with AWS (Automatic Weather Station) observation during the summer season (June - August, 2006). At first stage, the correction of initial state for each member was performed with respect to the observed values, and the corrected members get the training stage to find out an adaptive weight function, which is formulated by Root Mean Square Vector Error (RMSVE). It was found that the optimal training period was 1-day through the experiments of sensitivity to the training interval. We obtained the weighted ensemble average which reveals smaller errors of the spatial and temporal pattern of wind speed than those of the simple ensemble average.

• 대기
• /
• 제26권4호
• /
• pp.673-686
• /
• 2016

Understanding limitation of simulation for Planetary Boundary Layer (PBL) height in mesoscale meteorological model is important for accurate meteorological variable and diffusion of air pollution. This study examined the accuracy for simulated PBL heights using two different PBL schemes (MYJ, YSU) in Weather Research and Forecasting (WRF) model during the radiosonde observation period. The simulated PBL height were verified using atmospheric sounding data obtained from radiosonde observations that were conducted during 5 months from August to December 2014 over the Gumi weir in Nakdong river. Four Dimensional Data Assimilation (FDDA) using radiosonde observation data were conducted to reduce error of PBL height in WRF model. The assessment result of PBL height showed that RMSE with YSU scheme were lower than that with MYJ scheme in the day and night time, respectively. Especially, the WRF model with YSU scheme produced lower PBL height than with the MYJ scheme during night time. The YSU scheme showed lower RMSE than the MYJ scheme on sunny, cloudy and rainy day, too. The experiment result of FDDA showed that PBL height error were reduced by FDDA and PBL height at the nudging coefficient of $3.0{\times}10^{-1}$ (YSU_FDDA_2) were similar to observation compared to the nudging coefficient of $3.0{\times}10^{-4}$ (YSU_FDDA_1).

• Water Engineering Research
• /
• 제1권1호
• /
• pp.25-37
• /
• 2000

This study presents some results of a preliminary study for the coupled precipitation and river flow prediction system. The model system in based on three numerical models, Mesoscale Atmospheric Simulation model for generating atmospheric variables. Soil-Plant-Snow model for computing interactions within soil-canopy-snow system as well as the energy and water exchange between the atmosphere and underlying surfaces, and TOPMODEL for simulating stream flow, subsurface flow, and water tabled depth in an watershed. The selected study area is the 2,703 $\alpha_4$ $\km_2$ Soyang River basin with outlet at Soyang dam site. In addition to providing the results of rainfall and stream flow predictions, some results of DEM and GIS application are presented. It is obvious that the accurate river flow predictions are highly dependant on the accurate predictation predictions.

• 한국지구과학회지
• /
• 제26권1호
• /
• pp.66-77
• /
• 2005

한반도 남서해안에 위치한 흑산도 고층관측이 2003년 6월 1일부터 실시되고 있다. 이러한 흑산도 관측자료에 의한 수치예보개선효과를 보기 위하여 광주의 관측자료와 비교 분석하였다. 분석에는 MM5를 기본으로 제작한 호남지방 고밀도 예측시스템을 이용하였다. 먼저 지표면 마찰과 현열플러스의 차이에 의하여 광주와 흑산도의 바람장과 온도장은 다르게 나타났으며, 광주와 흑산도의 자료를 모두 동화시킨 수치예측 바람장과 기상장이 관측과 제일 잘 일치하였다. 강수면에서 비록 강수량은 과소평가를 하고 있으나, 강수시간과 강수구역은 흑산도자료를 포함하여 자료동화를 시킨 경우 관측과 유사하게 나타났다.

• 한국환경과학회지
• /
• 제11권4호
• /
• pp.281-288
• /
• 2002

This study was carried out for reading the change of local meteorological environment according to dam construction of Nakdong-river using numerical model. The study used PSU/NCAR Mesoscale Model version5(MM5) for inquiring effect of formation of artificial lake after dam construction. The colleague simulated temperature mixing ratio, latent heat flux and sensible heat flux in two cause of existing lake and not. Temperature and mixing ratio in southwest of Andong lake increased because of the air that was warm and moist above the lake moved to southwest due to the northeasterly wind. In the case of existing lake around Andong, latent heat flux increased much in the daytime after sunrise. However, sensible heat flux decreased but it didn't change distinctly in southwest of Andong like the other values.

• 대기
• /
• 제18권4호
• /
• pp.339-354
• /
• 2008

A numerical simulation of a heavy snowfall event that occurred 13 January 2008 along the Yeongdong coastal area, was performed using WRF (Weather Research and Forecasting) in order to reveal mesoscale structures and to construct a conceptual model showing the meteorological background that caused the large difference in snowfall amounts between the Yeongdong mountain area and the Yeongdong coastal area. The simulation results matched well with various observations such as corresponding 12h-accumulated observed precipitation, surface wind obscrvation, radar echoes, and satellite infrared images. The simulation and the observations showed that the scale of the event was of meso - $\beta$ and meso - $\gamma$ scale. The simulation represented well the mesoscale process causing the large difference in snowfall amounts in the two areas. First, wind flow was kept, to a certain extent, from crossing the mountains due to the blocking effect of the low Froude number (~1). The northeast flow over the adjaccnt sea tumcd northwest as it approachcd the mountains, where it was trapped, allowing so-called cold air damming. Second, a strong convergence area formed where the cold northwest flow along the Yeongdong coastal area and the relatively warm and moist northeast flow advecting toward the coast met, supporting the fonllation of a coastal front. Thus, the vertical motion was strongest over the front located near the coast, leading to the heavy snowfall there rather than in the remote mountain area.

• 한국지구과학회지
• /
• 제30권4호
• /
• pp.464-477
• /
• 2009

호수에 의한 국지 순환의 영향을 조사하기 위하여 대청호수 주변에 대하여 수치 실험을 수행하고 국지 순환의 형태를 연구하였다. WRF 모델로부터 예보된 지상 기온은 관측보다 작으며, 풍속은 모델에서 관측보다 강하게 모의됨을 보였다. 호수 주변의 국지 순환은 호수와 주변 지면과의 열적 차이에 의해 발생하는 호수풍이 특징적이었다. 대청호수에서는 호수풍이 09 LST에 발생하며, 15 LST에 최대를 보이고 18 LST에 소멸하였다. 수치 모의된 연직 순환의 높이는 1,200m를 나타냈다. 비습의 분포는 낮 시간동안 호수풍 순환에 의해 호수위의 습윤한 공기의 내륙 이동으로 주위 지면에서 증가함을 보였다. 호수를 제거한 민감도 실험에서 호수가 존재할 때 주위 지면 온도가 감소함을 보였다. 호수 지표이용도를 초원으로 변경하였을 때 호수 주변의 기상관측소에서 풍속은 증가하였다. 수치실험은 호수로부터 발생된 호수풍 순환이 주위 대기경계층 기상에 영향을 주고 있음을 지시한다.

• 한국환경과학회지
• /
• 제25권12호
• /
• pp.1597-1611
• /
• 2016

A numerical assessment using mesoscale-CFD (computational fluid dynamics) coupled A2C (atmosphere to CFD) model was carried out to analyze the variation of microscopic air flow pattern due to the construction of the Chilgok barrage in the Nakdong River. Scenarios with air flow patterns were classified into pre- and post-construction. The increased width of the river due to the construction of the Chilgok barrage induced obvious changes in moisture and the thermal environment around the river. However, air temperature variation was restricted within an area along the windward side in the numerical assessment. The impact of barrage construction on air temperature tends to be stronger during the nighttime than the daytime. It also stronger during the winter than the summer. In the simulation, the convergence of mesoscale wind is more pronounced after barrage construction than before. This is caused by the change of heat flux pattern induced by the widening of the river. Although this work is a case study with restricted atmospheric stability conditions that has several limitations in the numerical simulations, the impacts of the land-use changes brought about by the construction of the barrage in the river acceptable.