ENSO-Related Southern Hemisphere Blocking Dynamics

Zhang, Bo1; Dong, Li1,2; Ding, Hairu1,3; Xie, Zhiang1

2023-08-27

10.1029/2022JD038087

JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES   影响因子和分区

2169-897X

2169-8996

This study establishes a new blocking climatology in the Southern Hemisphere (SH) by using the improved detection method with the reanalysis data from 1979 to 2016. Furthermore, it investigates the dynamical linkage between SH blocking and ENSO phases. It is found that the ENSO warm phase is more conducive to the blocking formation than the cold phase while the blocking intensity is not affected by the ENSO phases. In addition, blocking in ENSO warm phase is characterized with upper-level divergence anomaly and the cold phase with convergence anomaly equatorward of blocking onset region. Through the diagnostic analysis of tropopause divergence for the composite blocking events via an improved divergence tendency equation, the study shows that the ageostrophic effect exhibits dual effects, namely, it induces anticyclonic ageostrophic vorticity favoring the formation of blocking whereas it results in convergence anomaly close to the blocking onset region thus inhibiting blocking locally. In addition, the nonlinear term in the divergence tendency equation is found to be a dominant forcing for favoring blocking onset. Nevertheless, despite the primary contributions from the ageostrophic effect and nonlinear term to blocking formation, they could barely explain the SH blocking onset preference in ENSO warm phase. Finally, through the localized Eliassen-Palm flux this study reveals that in ENSO warm phase the composite blocking onset region and the immediate upstream region are characterized by more localized EP flux convergence, thereby leading to more effective westerly wind weakening and favoring the blocking formation.

SCI

英语

第一 ; 通讯

National Natural Science Foundation of China[41975060] ; Shenzhen Science and Technology Program["JCYJ20190809163007701","JCY20200925160922002"]

Meteorology & Atmospheric Sciences

Meteorology & Atmospheric Sciences

WOS:001057469600001

AMER GEOPHYSICAL UNION

GEOSCIENCES

Web of Science

1.Southern Univ Sci & Technol, Dept Earth & Space Sci, Shenzhen, Peoples R China
2.Southern Univ Sci & Technol, Acad Adv Interdisciplinary Studies, Shenzhen, Peoples R China
3.Max Planck Inst Meteorol, Hamburg, Germany

Zhang, Bo,Dong, Li,Ding, Hairu,et al. ENSO-Related Southern Hemisphere Blocking Dynamics[J]. JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES,2023,128(16).

Zhang, Bo,Dong, Li,Ding, Hairu,&Xie, Zhiang.(2023).ENSO-Related Southern Hemisphere Blocking Dynamics.JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES,128(16).

Zhang, Bo,et al."ENSO-Related Southern Hemisphere Blocking Dynamics".JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 128.16(2023).