- 著者
- Yousuke Yamashita Hideharu Akiyoshi Makoto Inoue
- 出版者
- 公益社団法人 日本気象学会
- 雑誌
- SOLA (ISSN:13496476)
- 巻号頁・発行日
- pp.19B-002, (Released:2023-10-18)
The dynamical response of the southern hemisphere stratosphere to the ocean-surface conditions in 2002 and 2019, when exceptional sudden stratospheric warming (SSW) events occurred, was examined through the chemistry–climate model and experiments with 1,000 ensemble members using the sea-surface temperature (SST) and sea-ice conditions. Planetary waves propagating from the troposphere to the stratosphere in experiments using the ocean-surface conditions in 2002 and 2019 were markedly enhanced compared to those in experiments using climatological ocean conditions, owing to the enhancement of the zonal wavenumber-2 component in August 2002 and the wavenumber-1 component from August to November 2019. The distribution function from the ensemble members of the Antarctic polar-vortex intensity shifted to a weaker side in the 2002 and 2019 experiments relative to that of the climatological ocean conditions. The planetary wave propagation to the stratosphere was more enhanced in 2019 than in 2002 from austral winter to spring. This result is consistent with the weakening of the Antarctic polar-vortex intensity in the 2019 experiment relative to the 2002 experiment. These results suggest that the SSWs in 2002 and 2019 are closely related to the ocean surface conditions in these years through wave propagation in the troposphere and stratosphere.
- 著者
- Yousuke YAMASHITA Hideharu AKIYOSHI Theodore G. SHEPHERD Masaaki TAKAHASHI
- 出版者
- Meteorological Society of Japan
- 雑誌
- 気象集誌. 第2輯 (ISSN:00261165)
- 巻号頁・発行日
- vol.93, no.6, pp.629-644, 2015 (Released:2016-01-13)
- 参考文献数
- 52
- 被引用文献数
- 7 9
The combined influences of the westerly phase of the quasi-biennial oscillation (QBO-W) and solar maximum (Smax) conditions on the Northern Hemisphere extratropical winter circulation are investigated using reanalysis data and Center for Climate System Research/National Institute for Environmental Studies chemistry climate model (CCM) simulations. The composite analysis for the reanalysis data indicates strengthened polar vortex in December followed by weakened polar vortex in February-March for QBO-W during Smax (QBO-W/Smax) conditions. This relationship need not be specific to QBO-W/Smax conditions but may just require strengthened vortex in December, which is more likely under QBO-W/Smax. Both the reanalysis data and CCM simulations suggest that dynamical processes of planetary wave propagation and meridional circulation related to QBO-W around polar vortex in December are similar in character to those related to Smax; furthermore, both processes may work in concert to maintain stronger vortex during QBO-W/Smax. In the reanalysis data, the strengthened polar vortex in December is associated with the development of north-south dipole tropospheric anomaly in the Atlantic sector similar to the North Atlantic oscillation (NAO) during December-January. The structure of the north-south dipole anomaly has zonal wavenumber 1 (WN1) component, where the longitude of anomalous ridge overlaps with that of climatological ridge in the North Atlantic in January. This implies amplification of the WN1 wave and results in the enhancement of the upward WN1 propagation from troposphere into stratosphere in January, leading to the weakened polar vortex in February-March. Although WN2 waves do not play a direct role in forcing the stratospheric vortex evolution, their tropospheric response to QBO-W/Smax conditions appears to be related to the maintenance of the NAO-like anomaly in the high-latitude troposphere in January. These results may provide a possible explanation for the mechanisms underlying the seasonal evolution of wintertime polar vortex anomalies during QBO-W/Smax conditions and the role of troposphere in this evolution.