Observations on changes in Korean Changma rain associated with climate warming in 2017 and 2018
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The period of prolonged summer rain in Korea called Changma was studied. Changma, also known as Meiyu in China and Baiu in Japan, is an integral part of the East Asian Summer Monsoon System. Until the 1980s, the Changma rainy season in Korea occurred from late June and July for 30 to 40 days or approximately 4 to 5 weeks. This study investigated whether changes have been observed in the timing and amounts of precipitation associated with Changma. From the analysis of meteorological data obtained in 2017 and 2018, it is observed that the length of the rainy season has shortened to 2 to 3 weeks in agreement with the earlier studies. Furthermore, during the rainy season, there were many days of no rain and partly cloudy days. Although an active elongated-linear Changma front was common in the past, it was found that an inactive Changma front with a large meridional amplitude has caused intermittent rain showers for several hours from linear convective cloud streaks. In recent years, this has produced large variations in rainfall amounts among regional measuring stations in Korea. Climate warming in the north side of the Changma front has resulted in less contrast with the warm-moist air in the south side of it from the Pacific Ocean. This has resulted in a weaker and inactive quasi-stationary front which has caused a discontinuous broken Changma front and sporadic showery days. It is also observed that maritime polar air mass, mP, over the Okhotsk Sea of far eastern Russia has not affected the Changma front over the Korean Peninsula. Overall, this study found that the characteristics of past Changma fronts have changed significantly in recent years. The present observations imply the need of further studies on climate change and summer rainfall including water management.
KeywordsChanges of Changma rain in Korea Shortened Changma season with climate change Changma-Meiyu-Baiu rain Torrential rain showers with a Changma front Regional bias in summer rainfall amounts
We thank the KMA for providing science subvention of the Project (KMI2017-7020). Also, Ms. Cho JH has drawn a figure.
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