TY - JOUR
T1 - Characteristics and causes of Taiwan's extreme rainfall in 2022 January and February
AU - Huang, Shao Chin
AU - Huang, Wan Ru
AU - Wu, Yi chao
AU - Yu, Yi Chiang
AU - Chu, Jung Lien
AU - Jou, Ben Jong Dao
N1 - Funding Information:
Fig. 9a demonstrates a positive relationship between the increase in JF rainfall in Taiwan and the southwesterly moisture flux transport at 700 hPa, which mostly extends from the western SCS to Taiwan and south of Japan. There is also a weak positive relationship over north of the BoB; however, this is located behind the India-Burma Trough and is not connected to the positive relationship over SCS (Fig. 9a). Relative to JF climate (Fig. 9a), both pre-2002 and post-2002 periods (Fig. 9b–c) show an increase in moisture transport from SCS to support the increase in JF rainfall in Taiwan. However, the area with moisture transport passed the significant test at a 90% confidence interval extended to the southeastern BoB only for the post-2002 period (Fig. 9d). These features are consistent with those inferred from SSTA changes (Fig. 8), suggesting that the enhanced moisture needed to support the increase in JF rainfall in Taiwan originates from SCS for the pre-2002 period and that the enhanced moisture source extended westward to the southeastern BoB for the post-2002 period. It is likely that the enhanced atmospheric moisture pattern extending all the way from the southeastern BoB to SCS supports the active convection zone observed in JF 2022; this is consistent with what is observed in Fig. 7. This increasing impact of SSTA changes over the southeastern BoB might be one of the possible explanations for the observed increase in the maximum JF rainfall in Taiwan over the post-2002 period.We thank the data provider of Global Precipitation Climatology Project (https://psl.noaa.gov/data/gridded/data.gpcp.html), ECMWF Reanalysis v5 (https://www.ecmwf.int/en/forecasts/dataset/ecmwf-reanalysis-v5), and the Optimum Interpolation Sea Surface Temperature dataset version 2 (https://psl.noaa.gov/data/gridded/data.noaa.oisst.v2.html). W.-R. Huang was supported by the National Science and Technology Council of Taiwan under MOST 111-2111-M-003-006.
Funding Information:
We thank the data provider of Global Precipitation Climatology Project ( https://psl.noaa.gov/data/gridded/data.gpcp.html ), ECMWF Reanalysis v5 ( https://www.ecmwf.int/en/forecasts/dataset/ecmwf-reanalysis-v5 ), and the Optimum Interpolation Sea Surface Temperature dataset version 2 ( https://psl.noaa.gov/data/gridded/data.noaa.oisst.v2.html ). W.-R. Huang was supported by the National Science and Technology Council of Taiwan under MOST 111-2111-M-003-006 .
Publisher Copyright:
© 2022 The Authors
PY - 2022/12
Y1 - 2022/12
N2 - Over the past 40 years (1982–2021), the January and February (JF) rainfall in Taiwan has shown a clear decreasing trend. However, in 2022, the JF rainfall suddenly climbed to the third-highest value ever recorded in Taiwan. This study aims to explore the characteristics and causes of this unique event. Our results show that the significant increase in JF 2022 rainfall is contributed by both an increase in rainfall occurrence frequency and an increase in rainfall intensity. Further analysis shows that most of the JF 2022 rainfall is contributed by the rainy systems propagating from South China or the north of South China Sea to Taiwan but without the frontal structure, which is different from the general concept that JF rainfall is dominated by winter monsoon circulation-induced orographic rainfall and frontal rainfall. As a result, southern Taiwan experienced more than a 130% increase in JF 2022 rainfall compared to the JF climate mean. Possible physical explanations for the increase in JF 2022 rainfall can be attributed to the enhanced winter background circulation, which featured an enhanced regional northeasterly wind at 925 hPa coupled with an enhanced southwesterly wind transporting moisture at 700 hPa covering the domain of (10°-30°N, 100°-120°E). Consequently, an active convection zone extending from the southeastern Bay of Bengal to Taiwan was revealed in JF 2022 to result in the extreme rainfall in Taiwan. Further analysis also indicates that the relationship between the Taiwan JF rainfall and the tropical sea surface temperature has changed since 2002.
AB - Over the past 40 years (1982–2021), the January and February (JF) rainfall in Taiwan has shown a clear decreasing trend. However, in 2022, the JF rainfall suddenly climbed to the third-highest value ever recorded in Taiwan. This study aims to explore the characteristics and causes of this unique event. Our results show that the significant increase in JF 2022 rainfall is contributed by both an increase in rainfall occurrence frequency and an increase in rainfall intensity. Further analysis shows that most of the JF 2022 rainfall is contributed by the rainy systems propagating from South China or the north of South China Sea to Taiwan but without the frontal structure, which is different from the general concept that JF rainfall is dominated by winter monsoon circulation-induced orographic rainfall and frontal rainfall. As a result, southern Taiwan experienced more than a 130% increase in JF 2022 rainfall compared to the JF climate mean. Possible physical explanations for the increase in JF 2022 rainfall can be attributed to the enhanced winter background circulation, which featured an enhanced regional northeasterly wind at 925 hPa coupled with an enhanced southwesterly wind transporting moisture at 700 hPa covering the domain of (10°-30°N, 100°-120°E). Consequently, an active convection zone extending from the southeastern Bay of Bengal to Taiwan was revealed in JF 2022 to result in the extreme rainfall in Taiwan. Further analysis also indicates that the relationship between the Taiwan JF rainfall and the tropical sea surface temperature has changed since 2002.
KW - East Asian monsoon region
KW - Extreme winter rainfall event
KW - Multiple timescale variations
UR - http://www.scopus.com/inward/record.url?scp=85143300297&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85143300297&partnerID=8YFLogxK
U2 - 10.1016/j.wace.2022.100532
DO - 10.1016/j.wace.2022.100532
M3 - Article
AN - SCOPUS:85143300297
SN - 2212-0947
VL - 38
JO - Weather and Climate Extremes
JF - Weather and Climate Extremes
M1 - 100532
ER -
