Abstract
We examined the sea-breeze-initiated rainfall in the Seoul Metropolitan area (SMA) on 6 July 2017 using the weather research and forecasting (WRF) model. The model captures the arrival of the sea breeze front (SBF), the development of afternoon rainfall in the SMA, and the location of the sea-breeze-initiated maximum rainfall in the northeastern SMA reasonably well but overestimates the subsequent rainfall. We conducted sensitivity tests to better understand the urban effect on the sea-breeze-initiated rainfall event. Through factor separation analysis, we first examined the explicit role of sea and urban effect on sea-breeze-initiated rainfall. The results show that the interaction of sea and urban effects cause rainfall in the northwest and northeast of the SMA, indicating that both urban heat island circulation (UHIC) and sea breeze play an important role in the study case’s rainfall. We further examined the relative role of urban roughness and anthropogenic heat on the sea-breeze-initiated rainfall through factor separation analysis. Both anthropogenic heat and urban roughness play a role in increasing precipitation in the northeastern area of the SMA, with a larger contribution of anthropogenic heat than urban roughness. The relationship between low-level convergence at the SBF and urban factors is discussed.
Highlights
We further examined the relative role of urban roughness and anthropogenic heat on the sea-breezeinitiated rainfall through factor separation analysis
We evaluated the performance of the weather research and forecasting (WRF) model in simulating the sea-breeze-initiated precipitation in the Seoul Metropolitan area (SMA) against observations taken from automated weather station (AWS) and wind lidar on 6 July 2017
The location of sea-breeze-initiated maximum precipitation is associated with hot spots in the northeastern valley, which form as a result of topography as well as urban effects [12]
Summary
The sea-breeze-initiated rainfall at coastal areas has been investigated in many studies [2,4,5,6]. Shepherd et al [5] investigated the urban impact on coastal precipitation in Houston and found that two urban-induced features, convergence zones, and an urban low-pressure perturbation appear to be important factors leading to enhanced rain clouds in conjunction with the sea breeze. The interaction of local winds such as sea breeze, urban breeze, and valley breeze on a clear day in the SMA has been studied by Ryu and Baik [12] They reported that the sea breeze inland penetration speed slows due to rough roughness at a coastal city, Incheon, but it accelerates at an inland city, Seoul, due to urban heat island circulation (UHIC). We examined the urban effect on sea-breeze-initiated rainfall in the SMA. Factor separation was performed to examine the relative role of sea breeze and urban effect on the rainfall amount and distribution
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