RESULT
1. X-Direction Wind
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All cases had the maximum wind speed at near 08 UTC, which is 5 pm in Korean time. However, this includes some inaccuracies because this graph shows all of the grid points, the maximum wind speed shows near the center of land(120th grid point). More accurate result of the time when Sea Breeze occurs can be found in [graph number 5] below.
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Also, the maximum wind speed is 7-8m/s, and it is getting faster as it blows toward the center of land (120 grid point). When you see ‘Max Wind Location Timeseries’, the easterly wind shows Land breeze, and the westerly wind shows Sea Breeze in 01-08 UTC. At night time, there’s a reversed result. According to the table below, most values of Realistic case is equal to the Urban case.
2. Z-Direction Wind & Wind Velocity
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We expected that the maximum value of the z-direction wind velocity would be appear at 05-06 UTC, but in our model, it appear at 09-11 UTC. Sea Breeze moves from coast to inland, and we think that this migration process has affected the time when z-direction wind velocity is maximized.
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Overlaying a typical Sea Breeze schematic and our 3 km x-direction wind velocity contour graph, the inflow layer has a height of about 1 km as shown in the figure. Comparing the ‘3 km z-direction wind and temperature contour’ with the ‘1 km x-z wind velocity contour graph’, the z-direction wind velocity increases near the boundary of the layer, where inflow layer and frontal zone merge into each other, as x-direction wind flows in the inland direction. As a result, it was confirmed that strong updraft was developed in the frontal zone as the air was pushed into the inland by the Sea Breeze. This updraft is also associated with fast temperature rise in the daytime inland.
3. Temperature and Wind Vector
Generally, Sea Breeze is observed stronger, and faster than Land Breeze. Also, compared among other cases, Urban and Realistic case shows a bigger degree of weakness of Land Breeze.
4. Wind Velocity Distribution for Each Time
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Compared with Mixed case, Urban and Forest case, inland air parcel and Land Breeze do not meet in Mixed Urban region, Land Breeze intensity is smaller than Urban case and Forest case. In Urban case and Forest case, inland air parcel and Land Breeze meet and wind intensity is faster than Mixed case. Therefore, the Land Breeze becomes stronger when the inland air parcel is combined with the Land Breeze.
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In addition, when the Mixed case and the Urban case are compared, the diffusion rates of the Sea Breeze are similar and the time of Land Breeze occurrence is earlier in the Mixed Urban region. Comparing the Forest case with the Mixed case, the diffusion rate of Sea Breeze is faster in Mixed and Land Breeze occurs in Mixed Forest region. This means that the speed at which the air parcel moves on the surface differs for each LANDUSE type.
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In other words, it can be expected that the friction on the surface behaves differently for each LANDUSE, which is related to the Roughness Length, which is one of the variables of LANDUSE.
5. X-Direction Wind Vertical Profile by SFZ0
The larger the roughness Length, the greater the friction with the ground, so the wind intensity around 200 m is inversely proportional to the value of SFZ0. However, since the updraft wind also develops with the increase of the Roughness Length, the value of SFZ0 is proportional to the wind strength at about 1km.
6. X-Direction Wind Timeseries by SFZ0
![[최종] timeseries_SFZ0.png](https://static.wixstatic.com/media/22d729_8fcea7fc9c4a48009a5792a4ceffc494~mv2.png/v1/fill/w_694,h_669,al_c,q_90,usm_0.66_1.00_0.01,enc_avif,quality_auto/%5B%EC%B5%9C%EC%A2%85%5D%20timeseries_SFZ0.png)
A region near the sea (Yeongjongdo and Donghae) have a shorter time to reach sea-breeze for sure. The closer the region is to the ocean (Yeongjongdo and Donghae), the more distinct Land Breeze is observed. If the region is in inland (Gurorang River), the deviation from Roughness Length is larger than the observatory station near the ocean.
7. X-Direction Wind Timeseries by
LANDUSE Index & Correlation of
U 10 : Observation and Model
![[table] correlation.PNG](https://static.wixstatic.com/media/22d729_881939795444402cbfa58b09424b9a19~mv2.png/v1/fill/w_626,h_555,al_c,q_85,usm_0.66_1.00_0.01,enc_avif,quality_auto/%5Btable%5D%20correlation_PNG.png)
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In the Yeongjongdo and Donghae stations adjacent to the coastline, the correlation between model calculated data and observation data was significant (R2 is larger than 0.6), whereas in Guro and Hangang stations, the model and observation data were quite different. In actual cases, terrestrial heights and building layout, as well as LANDUSE, have a great influence on the landing of the west coast Sea Breeze toward inland of Seoul. Therefore, it is obvious that the accuracy of the inland model data is lower than that of the coastline. Also, the linear regression results of Yeongjongdo and Donghae stations illustrate that coefficient(a) is generally less than 1. This means that the model overestimates then the real cases. Also, in every case, since the y-intercept value is greater than zero, the easterly wind is estimated stronger and the westerly wind is estimated weaker.
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In Hangang station, R2 value is especially low among every LANDUSE cases. Hangang station is located right next to Han River. We used the 2-dimensional model with only x and z without y-direction components, which suggests that the effect of the Han River flowing in the east-west direction is not properly considered.