Evaluation of the Potential for Detecting MCS Causing Heavy Rainfall in the Korean Peninsula Based on Rawinsonde Data-Derived Instability Indices

Recent studies have shown an increase in frequency and intensity of heavy rainfall (Hev_Ran) events in the Korean Peninsula, located along the eastern coast of the Asian continent, due to global warming. Additionally, several studies have shown that the atmospheric environment and MCS(Mesoscale Convective Systems) causing Hev_Ran in East Asia differs from those in North America and Europe. Therefore, this study aims to reevaluate the possibility of detecting MCS causing Hev_Ran in Korea using 8 instability indices (Inst_Ind) (CAPE, KI, LI, SSI, SRH, SWEAT, TTI, and TPW) derived from rawinsonde data provided by the KMA(Korea Meteorological Administration). Considering the regional, seasonal, and temporal variations of Hev_Ran events in Korea, this study also conducts a detailed investigation on the detection capability of each instability index and optimize thresholds. For the recent ten years (2013~2022) during the rainy season (May~Sep), hourly accumulated precipitation data from the KMA and upper-air observation data from 8 rawinsonde stations in Korea were used for this purpose. While AWS measures precipitation every minute, rawinsonde observes the upper atmosphere twice (00 and 12UTC) or four times (00, 06, 12, and 18UTC) a day depending on the station. Thus, this study defines the collocated data as those AWS data within -2h~+2h temporally and 100km spatially based on Rawinsonde observations. Comparing the Inst_Ind during climate average (Cli_Ave) and Hev_Ran, significant differences were noted for KI, SWEAT, and TPW, with more than 20% differences between Cli_Ave and Hev_Ran for exceeding 30mm/h. However, CAPE, LI, SSI, SRH, and TTI did not show significant differences between Cli_Ave and Hev_Ran. POD and FAR were used to reevaluate the Hev_Ran detection level of the Inst_Ind, and the Hev_Ran detection level of the Inst_Ind was evaluated for various Hev_Ran intensity (30, 40, and 50 mm/h). Thresholds for Inst_Ind were used from the marginally instability levels suggested by KMA or the NOAA. The analysis has indicated usefulness in detecting Hev_Ran using SSI, KI, and TPW showing high POD(0.92~0.98) and FAR(0.91~0.99). However, detection levels using CAPE, LI, SWEAT, SRH were less effective regardless of Hev_Ran intensity, showing low POD (0.32~0.48) and high FAR (0.90~0.98). It was noted that while POD increases with higher Hev_Ran intensity, FAR also increases simultaneously.

This presentation will further detail the optimization of thresholds for Inst_Ind and provide a more detailed presentation of the detection capability of Hev_Ran systems and MCS, segmented by station and time.

This work was funded by the Korea Meteorological Administration Research and Development Program under Grant (RS-2023-00239653)