A numerical study of the interactions of urban breeze circulation with mountain slope winds
- 396 Downloads
The two-dimensional interactions of urban breeze circulation with mountain slope winds are investigated using the Weather Research and Forecasting (WRF) model coupled with the Seoul National University Urban Canopy Model (SNUUCM). A city is located near an isolated mountain, and there is no basic-state wind. Circulation over the urban area is asymmetric and characterized by the weakened mountain-side urban wind due to the opposing upslope wind and the strengthened plain-side urban wind in the daytime. The transition from upslope wind to downslope wind on the urban-side mountain slope occurs earlier than that on the mountain slope in a simulation that includes only an isolated mountain. A hydraulic jump occurs in the late afternoon, when the strong downslope wind merges with weaker mountain-side urban wind and stagnates until late evening. The sensitivities of the interactions of urban breeze circulation with mountain slope winds and urban heat island intensity to mountain height and urban fraction are also examined. As mountain height decreases and urban fraction increases, the transition from urban-side upslope wind to downslope wind occurs earlier and the urban-side downslope wind persists longer. This change in transition time from urban-side upslope wind to downslope wind affects the interactions between urban breeze circulation and mountain slope winds. Urban heat island intensity is more sensitive to urban fraction than to mountain height. Each urban fraction increase of 0.1 results in an average increase of 0.17 °C (1.27 °C) in the daytime (nighttime) urban heat island intensity. A simulation in which a city is located in a basin shows that the urban-side downslope wind develops earlier, persists longer, and is stronger than in the simulation that includes a city and an isolated mountain.
KeywordsUrban Heat Island Hydraulic Jump Mountain Slope Urban Heat Island Intensity Downslope Wind
The authors are grateful to two anonymous reviewers and Jaemyeong Mango Seo for providing valuable comments on this work. This work was funded by the National Research Foundation of Korea (NRF) grant funded by the Korea Ministry of Education, Science and Technology (MEST) (No. 2012-0005674).
- Pielke RA (2002) Mesoscale meteorological modeling, 2nd edn. Academic Press, San DiegoGoogle Scholar
- Simpson JE (1994) Sea breeze and local winds. Cambridge University Press, New YorkGoogle Scholar
- Skamarock WC, Klemp JB, Dudhia J, Gill DO, Barker DM, Duda MG, Huang XY, Wang W, Powers JG (2008) A description of the advanced research WRF version 3. NCAR, BoulderGoogle Scholar
- Zhang N, Wang X, Peng Z (2014) Large-eddy simulation of mesoscale circulations forced in inhomogeneous urban heat island. Bound-Layer Meteorol 151:179–194Google Scholar