“Distinct change of the wind in Water Bodies Case”

Through the wind vector plot, we can comprehensively see U-wind and W-wind that already has been examined through previous contour plots. In both cases, there is a near surface wind from the surrounding area to the urban area right after sunset. As discussed in the previous contour plots, the wind intensity of the water bodies case is generally greater than the mixed forest case, and after the midnight, we can see the near surface wind blowing from the center of urban area to water bodies area. When the center of convection moves from the outer area to the urban area, there is a near surface wind blowing from the outside to the center, but when the center of convection moves in the opposite direction, there is a near surface wind blowing from the center of urban area to the outside. Moreover, we can see that the intensity of the horizontal surface wind is generally greater than that of the near surface vertical wind.

Conclusion

Right after sunset, there is a wind blowing from the non-urban area to the center of urban area in both the mixed forest and the water bodies case, gradually decreasing the near surface air temperature and increasing the relative humidity near the surface from the outer area. And after midnight, both U-wind and W-wind gradually weaken and disappear in the mixed forest case, but in the case of water bodies, the center of convection moves from the center of urban area to water bodies area, and a near surface wind is observed blowing in the same direction.

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Overall, both U-wind and W-wind have larger values in the water bodies case, which indicates better air circulation in the city, but the relative humidity is relatively higher and the air layer with high temperature is thicker than the mixed forest case. Therefore we concluded that the mixed forest case is more suitable for mitigating the urban heat island phenomenon.