Characteristics of rainfall simulation over South Korea by summertime weather patterns according to the use of cumulus parameterization

The characteristics of summertime extreme rainfall events (ERE) according to the weather patterns in South Korea and compares the extreme rainfall model simulation skills depending on the use of cumulus parameterization has been studied. The WRF simulations with and without the a cumulus parameterization scheme (Kain–Fritsch cumulus scheme in this study) (CU_ON and CU_OFF experiment, respectively) are conducted over a 3 km high-resolution domain. The ERE-occurring days are clustered into four representative weather patterns (northern cyclonic circulation, frontal pattern between low and high, southwestern extratropical cyclone, and dominant positive geopotential height patterns) according to the 850 hPa geopotential height anomaly. As the occurrence dates of observed Clusters 1 and 2 overlap with a significant portion of the Korean summer monsoon season (Changma period), their rainfall is characterized by continuous low-intensity rainfall. In contrast, relatively high-intensity, short-duration rainfall occurs mainly in Clusters 3 and 4. The WRF experiments generally describe the clustered weather patterns well. For CU_ON, the spatial distribution of the daily rainfall anomaly composite in Clusters 1 and 2 is well depicted, but the overall rainfall intensity is underestimated. CU_ON better reproduces the Clusters 1 and 2 type rainfall characterized by long-duration rainfall than CU_OFF. The observed rainfall events exceeding 20 mm h⁻¹ intensity with a short-duration are reproduced better in CU_OFF than in CU_ON, showing reasonable performance for sub-daily time-scale rainfall in Clusters 3 and 4. Hence, the CU_ON well depicts the continuous low-intensity ERE type, while CU_OFF captures the ERE type where high-intensity rainfall with a short duration occurs relatively frequently.