Abstract
Record-breaking rainfall occurred over East Asia during the summer of 2020. However, in which aspect the summer of 2020 can be differentiated from the other years remains to be quantified. To this end, this study employs Markov chain analysis to quantify summer rainfall variability over East Asia using three Markov descriptors for heavy precipitation events of over 10 mm day−1: frequency, persistence, and entropy (i.e., irregularity). It is found that the heavy rainfall during the summer of 2020 can be attributed to an anomalously high frequency of rainfall in the central China and Japan and greater rainfall persistence over eastern China and Korea. Empirical orthogonal functions (EOFs) are used to analyze interannual variation in the descriptors using a few primary modes. For the summer 2020 period, the first and second modes for frequency account for the enhanced frequency over central China, and this is linked to sea surface temperature anomalies over the North Pacific, the equatorial eastern Pacific, and tropical Indian Ocean. For persistence, the first mode dominates the anomalous rainfall persistence observed during the summer of 2020. Similar but weak behavior can be also seen by the modes for entropy.
Highlights
Summer rainfall over East Asia (20°N–50°N, 100°E–150°E) is strongly linked with the East Asian summer monsoon (EASM; Wang and Linho 2002; Wang et al 2007) and is responsible for most of the annual mean rainfall for eastern and southern China, Korea, and Japan (Endo and Kitoh 2016)
The summer rainfall over East Asia has been considered a subsystem of the EASM and can be explained by the movement of a stationary front that leads to Meiyu in China, Changma in Korea, and Baiu in Japan
It is well known that the EASM is associated with various climate patterns such as the El Niño–Southern Oscillation (ENSO), global teleconnections, the Arctic Oscillation, the western North Pacific summer monsoon, and sea surface temperature (SST) variability
Summary
Summer rainfall over East Asia (20°N–50°N, 100°E–150°E) is strongly linked with the East Asian summer monsoon (EASM; Wang and Linho 2002; Wang et al 2007) and is responsible for most of the annual mean rainfall for eastern and southern China, Korea, and Japan (Endo and Kitoh 2016). The summer rainfall over East Asia has been considered a subsystem of the EASM and can be explained by the movement of a stationary front that leads to Meiyu in China, Changma in Korea, and Baiu in Japan. Complex changes in the front over East Asia that forms Meiyu, Changma, and Baiu should be investigated by multilateral factors using the frequency, persistence, and regularity of precipitation events, rather than the amount. We conduct Markov chain analysis to investigate the frequency, persistence, and entropy (i.e., irregularity) of summer rainfall over East Asia. This method was originally applied to ecological communities (Hill et al 2004) and was first adapted for meteorology by Mireruch et al (2010).
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