Abstract
We performed numerical experiments using an atmospheric general circulation model to assess the effect of convections associated with various tropical sea surface temperature (SST) fields on the tropical tropopause (TT). Three experiments were designed with different patterns of tropical SST: increasing and decreasing mean tropical SST, enhanced and weakened longitudinal gradient of tropical SST, and observed SST corresponding to strong El Niño–Southern Oscillation (ENSO) events. The results reveal that vertical advection plays an important role in controlling seasonal variation in TT temperature. In the case of a large (small) longitudinal gradient of tropical SST, the vertical eddy heat flux () diverges strongly (weakly) around the TT, resulting in cooling (warming) of the TT. Divergence of the vertical eddy heat flux is a primary controlling factor of variations in interannual TT temperature, especially during the peak of El Niño events. Analysis of ERA‐Interim and ERA‐40 data supports our results regarding the influence of vertical eddy heat flux on TT temperature. Divergence of vertical eddy heat flux at the TT layer is sensitive to the “strength” of the Matsuno‐Gill–type tropical stationary wave response; this divergence appears to explain variations in the observed TT temperature associated with ENSO.
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