|Last modified date：2021.06.08
Post-doctoral Fellow / Division of Earth Environment Dynamics / Research Institute for Applied Mechanics
|Last modified date：2021.06.08
|Masahiro Shiozaki, Takeshi Enomoto, Two Types of Mid-Latitudes Responses during La Niña, SOLA, 10.2151/sola.2021-016, 17, 0, 103-108, 2021.05.
|Shiozaki Masahrio, Enomoto Takeshi, Comparison of the 2015/16 El Niño with the two previous strongest events, SOLA, 10.2151/sola.2020-003, 2020.01,
The 2015/16 El Niño is compared with the two previous strongest events, the 1982/83 and 1997/98 El Niño. The 2015/16 winter features a basin warming in the Indian Ocean, a negative sea surface temperature (SST) anomaly shifted to the north in the western Pacific Ocean in addition to a positive SST anomaly shifted to the west in the eastern Pacific Ocean. These SST distributions lead to suppressed convection in the Maritime Continent, and to a weakened Hadley circulation in the western Pacific Ocean. The eastern Asian monsoon in the 2015/16 winter was also weakened due to the dominance of the western Pacific (WP) pattern. On the other hand, the third and fourth centers of action of Pacific/North American (PNA) pattern in the 2015/16 case are obscure. This may be due to weak divergence in the eastern Pacific Ocean..
|Masahiro Shiozaki, Takeshi Enomoto, Koutarou Takaya, Disparate Midlatitude Responses to the Eastern Pacific El Niño, Journal of Climate, 10.1175/jcli-d-20-0246.1, 34, 2, 773-786, 2021.01,
To investigate the disparate influences of the eastern Pacific (EP) El Niño on the winter climate in the Far East, we conducted composite analyses using long-term reanalysis datasets. Our analysis shows that the western Pacific (WP) pattern dominates in the warm winter (typical) composite and the Pacific–North American (PNA) pattern dominates in the non-warm winter (atypical) composite. In the warm winter case, the amplitudes of the negative sea surface temperature (SST) anomalies in the western Pacific Ocean are large whereas in the non-warm winter case, these amplitudes are small. In addition, the Indian Ocean basin warming occurs following the Indian Ocean dipole mode, as seen in the warm winter composite. We investigated the dynamical mechanisms responsible for the disparate midlatitude responses to the EP El Niño by focusing on Rossby wave sources and propagation. These SST anomalies modulate the Walker and Hadley circulations and the convective activity in the western Pacific Ocean. Upper-tropospheric divergences at the midlatitudes due to the anomalous Hadley circulation result in different teleconnection patterns. In the warm winter composite, the anticyclonic anomaly in the southern part of the WP pattern is created by the upstream negative Rossby wave source, while the other cyclonic anomaly is reinforced by the northward Rossby wave propagation. The cyclonic second and fourth centers of action of the PNA pattern are created by the positive Rossby wave sources. Furthermore, the equatorial SST gradient near the date line is found be a good precursor of the winter climate in the Far East..