Four-dimensional structures and physical process of the decadal abrupt changes of the northern extratropical ocean–atmosphere system in the 1980s

Authors

  • Dong Xiao,

    1. Chinese Academy of Meteorological Sciences, Beijing 100081, China
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  • Jianping Li,

    Corresponding author
    1. National Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Science, Beijing 100029, China
    • National Key Laboratory of Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences (CAS), Beijing 100029, China.
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  • Ping Zhao

    1. National Meteorological Information Centre, Beijing 100081, China
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Abstract

The four-dimensional structures and possible physical process of the decadal abrupt changes (DACs) of the northern extratropical ocean–atmosphere system in 1983–1988 are investigated by using ERSST.v2 and NCEP/NCAR reanalysis data. The DACs of sea surface temperature (SST) appeared over the southern tropical Atlantic, middle Pacific, and northern midlatitude oceans in 1983–1988. The atmospheric DACs in 1983–1988 were characterized with lower and higher geopotential height and air temperature anomalies over the Arctic and northern midlatitude, respectively. The above atmospheric distributions are attributed by the mass removal between the Arctic and middle latitudes. The decadal anomalies of the Ferrel cells and meridional atmospheric mass exchanges between the northern midlatitude and Arctic were suggestive of the DAC of the Northern Hemisphere annular mode (NAM).

Basing on the disclosed facts above, the possible physical process of the DACs in the 1980s is proposed as follows. The DACs of the northern midlatitude SST heated the lower tropospheric atmosphere and it made the meridional gradient of air temperature anomalies increase between the middle and high latitudes. Decadal anomalous Ferrel cell was triggered, which presented a meridional vertical current over the northern extratropics. The results of the meridional mass exchanges induced the lower geopotential height and air temperature over the Arctic, and higher ones over the northern midlatitude. In conclusion, the warming of the northern midlatitude SST may be responsible for the northern extratropical atmospheric DACs and associated climate change events in the 1980s. Copyright © 2011 Royal Meteorological Society

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