著者

NAOI Moeka KAMAE Youichi UEDA Hiroaki MEI Wei

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2020-027, (Released:2020-02-10)

被引用文献数

15

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Atmospheric rivers (ARs), narrow water vapor transport bands over the mid-latitudes, often cause great socio-economic impacts over East Asia. While it has been shown that summertime AR activity over East Asia is strongly induced by preceding-winter El Niño development, it remains unclear the extent to which seasonal transitions of El Niño Southern Oscillation (ENSO) from winter to summer affect the AR activity. Here we examine the relationship between the seasonal transitions of ENSO and the summertime AR activity over East Asia using an atmospheric reanalysis and high-resolution atmospheric general circulation model (AGCM) ensemble simulations. A rapid transition from preceding-winter El Niño to summertime La Niña results in more AR occurrence over northern East Asia via northward expansion of an anomalous low-level anticyclone over the western North Pacific compared to sustained or decayed El Niño cases. The northward expansion of the anticyclone is consistent with a steady response of the atmosphere to the anomalous condensation heating over the Maritime Continent and equatorial Pacific. Meridional positions of the extratropical AR occurrence and circulation anomalies are different between the reanalysis and AGCM simulations, which is possibly contributed by a limited sample size and/or AGCM biases and suggests that seasonal prediction of AR-related natural disaster risk over East Asia on a regional scale remains a challenge.

著者

UEDA Hiroaki MIWA Kana KAMAE Youichi

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2018-044, (Released:2018-05-14)

被引用文献数

13

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The response of tropical cyclone (TC) activity to the El Niño-Southern Oscillation (ENSO) and coherent sea surface temperate (SST) anomaly in the Indian Ocean (IO) is investigated with a particular focus on the decaying phase of El Niño. The TC anomalies are obtained from the database for Policy Decision making for Future climate change (d4PDF). This dataset is based on 100-member ensemble simulations for the period of 1951-2010 by use of the state-of-the-art atmospheric general circulation model (AGCM) forced with observed SST as well as the historical radiative forcing. AGCM utilized in the d4PDF is the Meteorological Research Institute Atmospheric General Circulation Model with about 60km horizontal resolution. Our analysis reveals a prolonged decrease in TC frequency over the tropical western Pacific during the post El Niño years until the boreal fall. Dominance of anomalous anticyclone (AAC) over the western Pacific induced by the delayed warming in the tropical Indian Ocean is the main factor for the suppressed TC activity rather than the local SST change. In contrast, the TC number over the South China Sea tends to increase during the post-El Niño fall (September to November). The physical reason can be ascribed to the weakening of AAC associated with the termination of IO warming. Thus we demonstrate that the effect of the IO warming should be taken into account when the ENSO is considered as an environmental factor for predicting TC activity.

著者

Ueda Hiroaki

出版者

筑波大学出版会

巻号頁・発行日

pp.1-264, 2014-03

著者

KURAMOCHI Masaya UEDA Hiroaki

出版者

公益社団法人 日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

pp.2023-002, (Released:2022-10-07)

被引用文献数

1

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The turnabout of air temperature anomalies over East Asia between the first and second halves of winter 2020/21 was examined from a teleconnection perspective with regionally different convective heating anomalies over the Indo-western Pacific sector. In the first half of winter 2020/21, the air temperature over East Asia was lower than normal, accompanied by a pair of anticyclonic and cyclonic anomalies in the upper troposphere southeast of the Tibetan Plateau and north of Japan, respectively. This dipole pattern is newly referred to as Southeast Asia–Japan (SAJ) pattern in this study, indicating the propagation of Rossby waves caused by enhanced tropical convection over the eastern Indian Ocean toward the South China Sea. In the second half of winter 2020/21, the enhanced convection shifted eastward to the Philippine Sea. The subsequent anticyclonic anomaly changed its position to the south of Japan, which was similar to the western Pacific (WP)-like teleconnection pattern, causing warmer conditions over East Asia. The composite analysis indicated that the anomalous anticyclone over the southeastern Tibetan Plateau corresponding to the SAJ pattern emerged simultaneously with intensification of convection over the South China Sea. Half of the cases of the WP-like pattern have been accompanied by enhanced convection over the Philippine Sea. The different circulation patterns were reproduced by prescribing the heat source over the South China Sea and Philippine Sea to the linear baroclinic model. Moreover, the vorticity budget analysis suggested that the presence of upper-tropospheric convergence of winds to the southeast of the Tibetan Plateau seen in the climatology is conceivable for the in situ localized anomalous circulation constituting the SAJ pattern due to vortex stretching effects.

著者

Kawase Hiroaki Yoshikane Takao Hara Masayuki Kimura Fujio Yasunari Tetsuzo Ailikun Borjiginte Ueda Hiroaki Inoue Tomoshige

出版者

American Geophysical Union

雑誌

Journal of geophysical research: Atmospheres (ISSN:2169897X)

巻号頁・発行日

vol.114, pp.D24110, 2009-12

被引用文献数

131 24

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Changes in the Baiu rainband owing to global warming are assessed by the pseudo global warming downscaling method (PGW-DS). The PGW-DS is similar to the conventional dynamical downscaling method using a regional climate model (RCM), but the boundary conditions of the RCM are obtained by adding the difference between the future and present climates simulated by coupled general circulation models (CGCMs) into the 6-hourly reanalysis data in a control period. We conducted the multiple PGW-DS runs using the selected Coupled Model Intercomparison Project Phase 3 (CMIP3) multimodel data set, giving better performance around East Asia in June, and the PGW-DS run using the multiselected CGCM model ensemble mean (PGW-MME run). The PGW-MME and PGW-DS runs show an increase in precipitation over the Baiu rainband and the southward shift of the Baiu rainband. The PGW-MME run has good similarity to the average of all PGW-DS runs. This fact indicates that an average of the multiple PGW-DS runs can be replaced by a single PGW-DS run using the multiselected CGCM ensemble mean, reducing the significant computational expense. In comparison with the GCM projections, the PGW-DS runs reduce the intermodel variability in the Baiu rainband caused by the CGCMs themselves.