Daytime Local Circulations and Their Interactions in the Seoul Metropolitan Area

Abstract

Daytime local circulations and their interactions in the Seoul, South Korea, metropolitan area are investigated using a high-resolution mesoscale model. It is found that the urban-breeze circulation interacts strongly with other local circulations, such as sea-breeze, cross-valley, and river-breeze circulations. Inland penetration of the sea breeze is retarded in the morning when moving over the coastal urban area because of the increased surface roughness but is accelerated in the afternoon after passing through the urban area as a result of the landward-convergent flow induced by urban heat islands in the inland urban areas. In the valley region, the cross-valley circulation prevails in the morning and the urban-breeze circulation prevails in the afternoon. The mountainside urban-breeze circulation weakens because of the cross-valley circulation in the opposite direction. On the other hand, the plainside urban-breeze circulation away from the mountain increases in strength as a result of the combined effect of heating from the urban surface and subsidence heating associated with the cross-valley circulation. This strengthened urban breeze acts to inhibit penetration of the sea breeze farther inland, causing the sea breeze to stagnate in Seoul. In the vicinity of the Han River, convergence zones with strong updrafts are formed as a result of the interaction between the urban breeze and the river breeze. When the sea-breeze front encounters the strong updrafts, the vertical velocity of the front at the intersection points increases.

High-resolution urban observation network for user-specific meteorological information service in the Seoul Metropolitan Area, South Korea

“…The surface thermal conductivity, heat capacity, and emissivity are estimated and verified by comparison with the surface temperature determined based on the EB and heat transfer models with observed surface temperature (Monteith and Unsworth, 1990;Santillan-Soto et al, 2015). The surface roughness and displacement lengths are obtained by a micrometeorological method and verified with those obtained from urban morphology data such as mean building height, frontal area density, and plane area density from the geographical information system (Macdonald et al, 1998;Kwon et al, 2014).…”

“…The urban area shows higher temperatures than the surrounding region throughout this period, which is mainly due to the heat capacity difference between the urban and rural regions and anthropogenic heat release. The temperature difference between the two land covers, that is, the urban heat island effect, becomes stronger during the night (Khan and Simpson, 2001;Freitas et al, 2007;Ryu and Baik, 2013). These temperature differences imply the possibility of local circulation such as land-sea breeze and urban-rural circulation.…”

The effect of urban geometry on mean radiant temperature under future climate change: a study of three European cities

“…For example, using sea breezes to improve outdoor thermal comfort in coastal areas has been widely discussed Papanastasiou et al 2010). However, the effect of sea breezes is rather limited in the study areas since the selected city centres are situated inland and the urban settlements reduce the inland penetration of sea breezes due to the increased surface roughness (Khan and Simpson 2001;Ryu and Baik 2013). Although reducing radiant heat load is the concern in the present study, the importance of wind components should be respected, especially in places where coastal sea breezes are abundant.…”

Surface Micro-Climate Analysis Based on Urban Morphological Characteristics: Temperature Deviation Estimation and Evaluation

“…Ryu and Baik (2012)은 WRF-UCM (Weather Research and Forecasting-Urban Canopy Model) (Masson, 2000;Kusaka et al, 2001;Martilli et al, 2002 관측을 통한 도시미기후 공간분포 산출방법은 관측 높이와 대상에 따라, 옥상 위 AWS 기온(air temperature)자료를 활용한 Canopy UHI 연구와 열적외선 (thermal infrared, TIR) 위성영상 기반 지표면온도(land surface temperature) 추정을 이용한 Surface UHI 연구 로 나눌 수 있다 (Bhang and Park, 2009;Jee et al, 2014;. 그러나 위성영상 자료는 시간해상도가 수 시간~수 일 사이로 매우 낮고 기상조건에 따라 관측 의 품질이 불균질 하다는 단점이 있다.…”