The tropical intraseasonal oscillation in SAMIL coupled and uncoupled general circulation models |
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| Authors: | YANG Jing BAO Qing WANG Xiaocong ZHOU Tianjun |
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| Institution: | State Key Laboratory of Earth Surface Processes and Resource Ecology,
Beijing Normal University, Beijing 100875;State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics,
Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029;State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics,
Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029;State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics,
Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029 |
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| Abstract: | Simulations of tropical intraseasonal oscillation (TISO) in SAMIL, the
Spectral Atmospheric Model from the Institute of Atmospheric Physics (IAP)
State Key Laboratory of Numerical Modeling for Atmospheric Sciences and
Geophysical Fluid Dynamics (LASG) coupled and uncoupled general circulation
models were comprehensively evaluated in this study. Compared to the
uncoupled model, the atmosphere--ocean coupled model improved the TISO
simulation in the following aspects: (1) the spectral intensity for the
30--80-day peak eastward periods was more realistic; (2) the eastward
propagation signals over western Pacific were stronger; and (3) the variance
distribution and stronger signals of Kelvin waves and mixed Rossby gravity
waves were more realistic. Better performance in the coupled run was assumed
to be associated with a better mean state and a more realistic relationship
between precipitation and SST. In both the coupled and uncoupled runs, the
unrealistic simulation of the eastward propagation over the equatorial
Indian Ocean might have been associated with the biases of the precipitation
mean state over the Indian Ocean, and the unrealistic split of maximum TISO
precipitation variance over the Pacific might have corresponded to the
exaggeration of the double Intertropical Convergence Zone (ITCZ) structure
in precipitation mean state. However, whether a better mean state leads to
better TISO activity remains questionable. Notably, the northward
propagation over the Indian Ocean during summer was not improved in the mean
lead--lag correlation analysis, but case studies have shown some strong
cases to yield remarkably realistic northward propagation in coupled runs. |
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| Keywords: | tropical intraseasonal oscillation atmosphere-ocean
interaction mean state northward propagation simulation |
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