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

Abstract

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. Statisticalanal ysis indicates that the 29-year mean annualrainfal l occurring with TCs within 3000 km of Korea is 658 mm, 49% of the 29-year total mean annualrainfal lof 1340 mm. About 32% of the totalmean annualamount 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 subtropicalhigh (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.© 2012 K.-Y. Byun and T.-Y. Lee.