Remote Effects of Tropical Cyclones on Heavy Rainfall over the Korean Peninsula

Remote effects of TCs on heavy rainfall over the Korean peninsula have been investigated through statistical, composite, and trajectory analyses and case studies. This study used the observed precipitation data from manned stations of the KMA, TC best track data archived by the RSMC, and JRA-25 data. The HYSPLIT model and the WRF model are utilized for trajectory analysis and case studies, respectively. Statistical analysis indicates that the 29-year (1981-2009) mean annual rainfall occurring with TCs within 3000 km distance is 658 mm, amounting to 49% of the 29-year mean annual total rainfall of 1340 mm. About 32% of the mean annual total amount occurs with TCs in the distance range of 1200-2800 km. The probability of heavy rainfall over the peninsula is higher with TCs that make landfall on southern and eastern China compared to other regions. In the heavy rainfall (HR) composite, the synoptic-scale pressure pattern during the remote TC events is characterized by a synoptic-scale trough to the northwest, a western Pacific subtropical high 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 entrance region, concurrent with a region of convective instability enhanced by strong moisture transport and quasi-geostrophic forcing for ascent by warm-air advection. The composite analysis shows that remote TCs can influence heavy rainfall over the peninsula by helping establish a convectively unstable environment and a large-scale convergence of air. Numerical simulation confirms the environment related to heavy rainfall over the Korean peninsula occurring with remote TCs. These results represents the moisture of remote TC's outer circulation affects the environment over the Korean peninsula, and induces convective instability. In trajectory analysis, air parcel's origin is associated with remote TC's circulation for heavy rainfall cases occurring with remote TCs. Moisture source region analysis presents the moisture transport into the Korean peninsula by remote TC's outer circulation affects heavy rainfall over the peninsula.