Possible Relationship between Korean Heat Wave and Western North Pacific Tropical Cyclone Genesis Frequency

This study conducted a correlation analysis between tropical cyclone genesis frequency (TCGF) in the western North Pacific (WNP) and heat wave days (HWD) in Korea during July and August for 46 years (1973–2018) and we found a strong positive correlation between them. This implied that the higher the TCGF in the WNP during July and August, the higher the HWD in Korea becomes. To examine the cause of the statistically significant positive correlation between the TCGF during July and August in the WNP and the HWD in Korea, 15 years with the highest frequency and the lowest frequency out of the 46 years in the TCGF time series were selected and defined as high TCGF years and low TCGF years, respectively. An analysis of the difference in 2m air temperature (Air2m) between the two groups showed that in the mid-latitude region of Asia, the Air2m was higher during the high TCGF years. Thus, it could be seen from this analysis that the increase of HWD during the high TCGF years is likely to occur in the entire mid-latitude region of East Asia as well as in Korea. According to the difference in atmospheric circulations between the two groups, in all layers of the troposphere, anomalous anticyclonic and cyclonic circulations were strengthened in the mid-latitude region of East Asia and in the WNP, respectively, which was similar to the Pacific-Japan (PJ) teleconnection pattern. Furthermore, the anomalous anticyclone strengthened in the mid-latitude region of East Asia was associated with the weakening of the East Asian summer monsoon, and the anomalous cyclone strengthened in the WNP was associated with the WNP summer monsoon. The difference in the vertical meridional circulation averaged over the longitude range where Korea is located showed that anomalous upward and downward flows were strengthened in the WNP and in the latitude where Korea is located, respectively. This implied that the local Hadley circulation was strengthened during the high TCGF years. An analysis of the difference in the mean sea surface temperature during July and August showed that the eastern Pacific (EP) La Niña was strengthened during the high TCGF years. To determine the cause of the formations of anomalous anticyclones in the mid-latitude region of East Asia and in the WNP during the high TCGF years, the 500 hPa wave activity flux was analyzed. The wave activity flux originated from the North Atlantic, passed through the Scandinavian Peninsula, the North coast of Russia, and East Siberia before reaching Korea and the WNP. This spatial distribution was similar to the Scandinavia teleconnection pattern. Therefore, we conclude that the anomalous anticyclone formed in the mid-latitude region of East Asia and the anomalous cyclone formed in the WNP during the high TCGF years are associated with the Scandinavia teleconnection pattern.