Possible combined effect of El Niño–Southern Oscillation and Pacific Decadal Oscillation on Korea affecting tropical cyclone passage frequency

• Published in: Atmospheric science letters 2020-10, Vol.21 (10), p.n/a
• Main Authors: Choi, Jae‐Won, Kim, Hae‐Dong
• Format: Article
• Language: English
• Subjects: Atmospheric sciences; Circulation anomalies; Cyclones; Cyclonic circulation; El Nino; El Nino effects; El Nino phenomena; El Nino-Southern Oscillation event; El Niño Southern Oscillation; Global warming; Hurricanes; Korea; Pacific Decadal Oscillation; Runoff; Southern Oscillation; Stream discharge; Stream flow; Time series; Tropical climate; Tropical cyclones; Westerlies; Wind
• ISSN: 1530-261X; 1530-261X
• DOI: 10.1002/asl.907

This study found that the passage frequency of tropical cyclones (TCs) affecting Korea has had negative correlations with the Pacific Decadal Oscillation (PDO) and the El Niño–Southern Oscillation (ENSO) since the early 1980s. To examine the actual combined effects of PDO and ENSO on the passage frequency of TCs affecting Korea, the positive PDO and ENSO years for 9 years and the negative PDO and ENSO years for 9 years were selected during the periods of 1951–1981 (pre‐1981) and 1982–2012 (post‐1981), and then the average difference between these two phases was analyzed. An analysis of anomalous stream flows at 500 hPa showed the formation of anomalous cyclonic circulations in an east‐to‐west direction from East Asia to the North Pacific both in the pre‐1981 and post‐1981 periods in the positive PDO and ENSO years. However, the anomalous cyclones in East Asia were stronger in the pre‐1981 period, whereas the anomalous cyclones in the North Pacific were stronger in the post‐1981 period. Consequently, China, Korea and the west of Japan were affected by strong anomalous northerlies in the pre‐1981 period, and the TC passage frequency was lower in these regions as a result. In the post‐1981 period, these countries were affected by anomalous northwesterlies or anomalous westerlies. The 15‐year sliding correlations between Korea affecting TC passage frequency and (a) Pacific Decadal Oscillation (PDO) index and (b) Niño‐3.4 index (for example, the correlation coefficient of 1961 is calculated for the period from 1961 to 1975), and time series between Korea affecting TC passage frequency and (c) PDO index and (d) Niño‐3.4 index for summer (July–September). In (a) and (b), the dashed line shows the 90% significant level.