Impacts of Topography on Airflow and Precipitation in the Pyeongchang Area Seen from Multiple-Doppler Radar Observations

Abstract

This study uses high-resolution radar and surface observations to investigate the finescale structural evolution of airflow and precipitation over complex terrain in the Pyeongchang area, South Korea. The Taebaek Mountain range (TMR) runs parallel to the northeastern coast of South Korea, with a perpendicular ridge known as the Pyeongchang branch (PCB). The objective of this study was to identify the mechanisms of wintertime precipitation over these topographic features during the passage of a low pressure system (LPS) through the southern Korean Peninsula. The analysis indicates that intense precipitation occurred over the southwestern and northeastern sides of the TMR during stage I but only over the northeastern side during stage II. The prevailing southwesterly winds were dominated by warm advection associated with the LPS over the PCB during stage I. These prevailing southwesterly winds locally enhanced precipitation on the southwestern end of the PCB; multiple influences of mountain waves, airflow convergence, and drifted particles are possible factors for causing precipitation on the northeastern side of the TMR. During stage II, the prevailing winds changed from easterlies to northeasterlies offshore from Gangneung. The easterly winds decelerated and were deflected locally along the mountainous coast, and this blocked zone interacted with the oncoming flow to trigger a precipitation band. Consequently, the northeasterly winds helped push the precipitation band toward the coast, causing heavy precipitation in Gangneung. The observational evidence presented shows that the interaction of temporally changing winds accompanying the movement of an LPS over topography is a critical factor for determining the distribution and intensity of precipitation.

Observational study for strong downslope wind event under fine weather condition during ICE-POP 2018

“…WISSDOM was originally developed by Liou and Chang (2009) and has been applied in the Pyeongchang area (Tsai et al, 2018). This study adopted a newly improved version, which includes more observations with more constraints compared with a previous version.…”

“…Liou et al, 2012Liou et al, , 2013Liou et al, , 2014Liou et al, , 2016Lee et al, 2017). The primary advantages and additional details of WISSDOM can be referred to Tsai et al (2018). The main improvement of the new version of WISSDOM is that all available wind observations are considered to be one of the constraints to minimize the cost function.…”

“…In mountain regions, wind is an important atmospheric phenomena as enhanced precipitation may be usually caused by the wind impinging topography (Medina et al, 2007;Yu and Cheng, 2008;Panziera and Germann, 2010;Houze, 2012;Yu and Tsai, 2017;Tsai et al, 2018).…”

“…TMR and northeastern coastal regions through the WISSDOM (WInd Synthesis System using DOppler Measurements, Liou and Chang, 2009;Tsai et al, 2018) synthesis. In particular, this study tries to recognize the mechanisms of the strong wind over the mountainous area and in the lee side areas of TMR while a LPS passing through the northern side of the Korean peninsula.…”

Decoupling between Precipitation Processes and Mountain Wave Induced Circulations Observed with a Vertically Pointing K-Band Doppler Radar

“…Using radar observations, it has been observed that the turbulence and small updraughts produced inside the shear layer enhance ice riming and raindrop coalescence that contributes to the growth of precipitation particles [5,6]. Combining radar observations and model simulations it has been found that mountain waves can modulate the precipitation patterns of the winter storms [7,8]. However, during a winter observational campaign, Kingsmill et al [9] observed a vertically propagating mountain wave forced by the Park Range (northern Colorado) using an airborne vertically pointing W-band (95GHz) Doppler radar.…”