Different Future Changes between Early and Late Summer Monsoon Precipitation in East Asia

Abstract

Future changes in East Asian summer monsoon (EASM) precipitation and the associated atmospheric circulation changes are investigated based on ensemble projections with the 60-km mesh Meteorological Research Institute atmospheric general circulation model (MRI-AGCM60). The projections at the end of the twenty-first century under the Representative Concentration Pathway 8.5 (RCP8.5) scenario indicate anoverall increase in EASM precipitation, but with large sub-seasonal and regional variations. In June, the Meiyu-Baiu rainband is projected to strengthen, with its eastern part (i.e., the Baiu rainband) shifted southward relative to its present-day position. This result is robust within the ensemble simulations. In July and August, the simulations consistently project a significant increase in precipitation over the northern East Asian continent and neighboring seas; however, there is a lack of consensus on the projection of the Meiyu-Baiu rainband in July. A small change in precipitation over the Pacific is another feature in August.Sensitivity experiments with the MRI-AGCM60 reveal that the precipitation changes in early summer are dominated by the effects of sea surface temperature (SST) warming (i.e., uniform warming and the tropical pattern change), which induce an increase in atmospheric moisture and a strengthening and southward shift of the upper-level East Asian westerly jet (EAJ), especially over the Pacific. On the other hand, the influence of land warming and successive large SST warming in the extratropics is evident in the precipitation changes in late summer. These late summer effects oppose and exceed the early summer effects through changes in the EAJ and low-level monsoon winds. These results suggest that the competition between the opposing factors makes the signal of the Meiyu-Baiu rainband response smaller in July than in June, and thus there tends to be a larger spread among simulations regarding the future tendency of the rainband in July.

Enhanced Role of Convection in Future Hourly Rainfall Extremes Over South Korea

“…It should be noted that large uncertainties can arise from inter‐GCM differences as well as internal climate variability. Changes in East Asian monsoon precipitation are uncertain due to inter‐GCM differences in dynamic effects, that is, monsoon circulation changes, more for mean precipitation (e.g., Endo et al., 2021; Ha et al., 2020). In contrast, extreme summer precipitation over East Asia is projected to increase with good inter‐model agreement, being determined by thermodynamic effects, that is, moisture increases with warming (e.g., Lee et al., 2018).…”

Historical trends in climate indices relevant to surface air temperature and precipitation in Japan for recent 120 years

“…Bar and closed circle represent numbers for 5 and 10% significance levels. The solid line represents effective number of stations due to indices that cannot be defined Baiu and Autumn rainy seasons via differences in upperlevel westerly wind changes (Endo et al, 2021). In addition, precipitation changes during mid-summer are projected to differ in sign, with a decrease in the Pacific region including the Kanto-Koushin to the Southern Kyushu regions, and an increase in the region of the Sea of Japan including the Hokuriku to North Kyushu regions (Ose, 2019).…”

“…The 51-station-mean frequencies of daily heavy precipitation greater than 100 or 200 mm and of 1-hr heavy precipitation have increased since 1901. These changes often feature some regional means of trends in indices as in Fujibe (2008), Fujibe et al (2006Fujibe et al ( , 2007, and Endo et al (2021), and the trends for each of all the 51 observation stations are not intensively examined.…”

Earlier Onset and Shortened Meiyu Season During the Last Interglacial Based on Dynamical Downscaling Simulations

“…Although there is no consensus on the long‐term trend of the onset, retreat, and duration of the Meiyu in the present day (Ding et al., 2020), investigations of the onset, retreat, and duration of the Meiyu in past climates and future scenarios generally suggest an earlier retreat and shortened duration of the Meiyu in a warmer state. Besides, the enhanced magnitude and frequency of extreme precipitation in the Meiyu season seen during the LIG was observed in the past several decades and projected at the end of the 21st century (Ding et al., 2020; Endo et al., 2021; Kitoh & Uchiyama, 2006). This points to increased extreme precipitation events during the Meiyu season in a warmer world.…”