Winter season stratospheric circulation in the SAMIL/LASG general circulation model |
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Authors: | Rongcai Ren Guoxiong Wu Ming Cai Jingjing Yu |
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Affiliation: | 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;Department of Meteorology, Florida State University, Tallahassee, Florida 32306, USA;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: | In this paper, we examine the performance of the 26-level version of the SAMIL/LASG GCM
(R42/L26) in simulating the seasonal cycle and perpetual winter mean stratospheric circulation as
well as its variability by comparing them with the NCEP/NCAR reanalysis. The results show that the
model is capable of reproducing many key features of the climatology and seasonal variation of the
stratospheric circulation despite that the model's mean polar vortex is stronger and more zonally
symmetric compared to the observation. Further diagnosis of the results from a perpetual-January-run
of the SAMIL/LASG GCM indicates that the dominant winter-season oscillation mode in the model's
stratosphere exhibits a similar inter-seasonal timescale with similar spatial patterns as those
inferred from the NCEP/NCAR reanalysis. In particular, the simulated polar vortex oscillation mode
exhibits a dominant inter-seasonal timescale of about 120 days, and is accompanied with the simultaneous
poleward and downward propagation of temperature anomalies in the stratosphere and the equatorward
propagation of temperature anomalies in the troposphere. More encouragingly, the 26-layer version
of the SAMIL/LASG GCM is able to produce three strong Stratospheric Sudden Warming events during
the 1825 days of perpetual-January integration, with the polar westerly jet completely reversed
for a few weeks without imposing any prescribed anomalous forcing at the lower boundary. |
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Keywords: | SAMIL/LASG GCM (R42/L26) winter stratospheric circulation |
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