Analysis for Onset of Changma Using Ieodo Ocean Research Station Data

et al. 2023

Journal of Climate

Marine heatwaves (MHWs) are among the most severe climatic events under global warming conditions; they damage marine ecosystems and result in socio-economic losses. In East Asia, the sea surface temperature (SST) has increased significantly and is projected to increase further. Considering such increases in SST over East Asia, studies on MHWs are needed to minimize the damage caused. In this study, we classified the spatiotemporal characteristics of East Asian MHWs during boreal summer with a self-organizing map for 39 years (1982–2020) and determined their unexplored possible mechanisms. Four dominant modes of MHWs across East Asia were identified: the (1) Subtropical Gyre, (2) East China Sea, (3) East Sea/Japan Sea, and (4) Yellow Sea modes. The total annual number of MHW days has increased by about 1.23 days/year. The significant trend is mainly determined by the Subtropical Gyre mode, whereas other modes do not exhibit significant trends. As the East China Sea mode could be linked to a strong East Asian summer monsoon (EASM), the resultant low-salinity water from the Yangtze (Changjiang) River could stratify the ocean and increase the water temperature. The East Sea/Japan Sea and Yellow Sea modes could be linked to remote forcings over the subtropics, leading to persistent anticyclonic circulation over East Asia. The anomalous anticyclone contributed to the MHWs occurrences by enhancing downward shortwave radiation and reducing entrainment cooling caused by Ekman downwelling. These findings have important implications for distinguishing the characteristics of East Asian MHWs and reveal the possibility of predicting them by identifying their precursors.

Section: A Reanalysis Datasets and Korea Ocean Research Stationsmentioning

confidence: 99%

Classification and Causes of East Asian Marine Heatwaves during Boreal Summer

et al. 2023

Journal of Climate

“…The observational data collected at the Ieodo Ocean Research Station (I-ORS), located within the northern basin of the ECS (32.12 • N, 125.18 • E), were used. The I-ORS platform is used to monitor atmospheric and oceanic variability across multiple timescales [27,28], such as TCs [29,30], MHWs [14], the EASM [31], and CDW [32]. We utilized daily water temperature and salinity, measured at 4.2, 20.5, and 38 m, by taking an average from 10 min interval from June to September for 19 years (2004-2022).…”

Section: Datamentioning

confidence: 99%

The record-breaking 2022 long-lasting marine heatwaves in the East China Sea

Chu

et al. 2023

Environ. Res. Lett.

Self Cite

In 2022, record-breaking long-lasting marine heatwaves (MHWs) occurred in the East China Sea (ECS), which persisted for 62 days during boreal summer. This exceeded the average MHWs duration of 10 days by a factor of 6. In addition, 2022 was also recorded as a year of many extreme events throughout Asia, such as summer floods in China and Pakistan, droughts and extreme heat in Europe, raising the question of whether they were caused by a “triple-dip” La Niña, which has persisted since September 2020. Here we examine the key local and remote processes that led to the 2022 MHWs in the ECS using mixed-layer heat budget analysis. During the onset of the MHWs, a salinity-stratified shallow mixed-layer due to the large river discharge from the Yangtze-Huaihe River floods in June enhanced warm ocean temperature in the ECS. Simultaneously, an anomalous anticyclone maintained by the stationary Rossby wave, which is generated by vorticity forcings in mid-latitudes and thermal forcing in Pakistan, settled in the corresponding region and led to the long-lasting MHWs until Typhoon Hinnamnor began to dissipate the wave in early September. This study improves our understanding of the physical mechanism of flood-related MHWs that have increased with recent climate change.

“…The peak rainy season (Changma) was also defined to look into the precipitation change during the peak season. Because the onset date of rainy season varies each year (Ha et al, 2005; KMA, 2011; Oh et al, 2014; Seo et al, 2011), climatologically defined peak rainy season was used to conduct the analyses. The Changma season is fixed as climatological rainy period when the 27‐day running average precipitation is the largest in the daily precipitation climatology (Figure 1).…”

Section: Data and Definition Of Rainy Seasonmentioning

confidence: 99%

Long‐term change of summer mean and extreme precipitations in Korea and East Asia

Intl Journal of Climatology

Cha

et al. 2023

The change of the precipitation characteristics over South Korea is investigated using long‐term (60 years) hourly precipitation records from surface stations focusing on extended summer (June–September) and rainy season (Changma). The precipitation characteristics including extreme events (>30 mm·h−1 or >100 mm·day−1) are also compared for the past (1961–1990) and recent (1991–2020) climatology. The amount of summer precipitation shows a notable increase over South Korea (2.6 mm·day−1·century−1) during the last 60 years (1961–2020) although it is smaller than recent 48‐year trend measured in North Korea (9.7 mm·day−1·century−1). Precipitation amounts are significantly increased than past climatology particularly in 70–100 and 200 mm·day−1 intensity ranges. The frequency of extreme precipitation also exhibits an increasing trend (1.0 frequency·century−1) during the last 60 years over South Korea. The frequency of extreme precipitation has been doubled in the recent climatology compared to the past climatology. Daily precipitations in top 1 percentile present clear increasing trends during the extended summer and Changma season in South Korea. Further investigation using gridded precipitation reveals that the similar mean and extreme precipitation increases are observed over the wider regions in East Asia, including central China and southern Japan. This result implies that the long‐term precipitation change over South Korea is related to a large‐scale circulation change in the East Asian summer monsoon.