The effect of transient eddy on interannual meridional displacement of summer East Asian subtropical jet |
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| Authors: | XIANG Yang YANG Xiuqun |
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| Institution: | Institute for Climate and Global Change Research, School of Atmospheric Sciences,
Nanjing University, Nanjing 210093;Institute for Climate and Global Change Research, School of Atmospheric Sciences,
Nanjing University, Nanjing 210093 |
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| Abstract: | Using ERA-40 reanalysis daily data for the period 1958--2002, this study investigated
the effect of transient eddy (TE) on the interannual meridional displacement of summer
East Asian subtropical jet (EASJ) by conducting a detailed dynamical diagnosis.
The summer EASJ axis features a significant interannual coherent meridional displacement.
Associated with such a meridional displacement, the TE vorticity forcing anomalies are
characterized by a meridional dipole pattern asymmetric about the climatological EASJ axis.
The TE vorticity forcing anomalies yield barotropic zonal wind tendencies with a phase meridionally
leading the zonal wind anomalies, suggesting that they act to reinforce further meridional
displacement of the EASJ and favor a positive feedback in the TE and time-mean flow interaction.
However, The TE thermal forcing anomalies induce baroclinic zonal wind tendencies that
reduce the vertical shear of zonal wind and atmospheric baroclinicity and eventually suppress the TE activity,
favoring a negative feedback in the TE and time-mean flow interaction. Although the two types of TE
forcing tend to have opposite feedback roles, the TE vorticity forcing appears to be dominant in the
TE effect on the time-mean flow. |
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| Keywords: | East Asian subtropical jet transient eddy vorticity forcing transient eddy thermal forcing |
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