Remote effects of tropical cyclones on heavy rainfall over the Korean peninsula - statistical and composite analysis

This study investigates the remote effects of tropical cyclones (TCs) on heavy rainfall (HR) over the Korean peninsula through statistical and composite analyses for 1981-2009. Statistical analysis indicates that the 29-year mean annual rainfall occurring with TCs within 3000 km of Korea is 658 mm, 49% of the 29-year total mean annual rainfall of 1340 mm. About 32% of the total mean annual amount occurs with TCs within the range of 1200-2800 km. The probability of HR over the peninsula is higher with TCs that make landfall on southern and eastern China compared to other regions. In the HR composite, the synoptic-scale pressure pattern during the remote TC events is characterised by a synoptic-scale trough to the northwest, a western Pacific subtropical high (WPSH) to the southeast and a TC to the southwest of the Korean peninsula. This pattern results in a region of strong rising motion located beneath the upper-level jet (ULJ) entrance region, concurrent with a region of convective instability enhanced by strong moisture transport and quasi-geostrophic (QG) forcing for ascent by warm-air advection. The composite analysis shows that remote TCs can influence HR over the peninsula by helping to establish a convectively unstable environment and a large-scale convergence of air.