The results show that there are two statistically steady regimes in the H-C parameter space. One regime is characterized by a double-jet state that resides only within the small H/large C part of parameter space. The other regime appears when H is large, and is characterized by a single-jet state. A linear theory offers an explanation for this regime behavior, and indicates that the characteristics of the state in each regime depend upon the strength of the subtropical jet. Moreover, the transition across these two regimes is often found to be abrupt. Again, this behavior is consistent with the bifurcation found in the linear theory. The implication is that the degree of climate sensitivity to heat sources/sinks depends on where the climatic state of interest resides in the parameter space.
Systematic changes are also found in the internal variability within each regime. In the single-jet regime (high H), the dominant form of internal variability represents north-south meander of the jet, known as the zonal index. On the other hand, in the double-jet regime (small H/large C), the internal variability is dominated by a remarkably periodic poleward propagation of zonal-mean flow anomalies.
We investigate the extent to which the dominant form of internal variability, within a given model run, is capable of predicting the zonal-mean climatology of other model runs with different values of H and C. It is found that this type of climate predictability is generally high in the single-jet regime, but it is low in the double-jet regime where the quasi-periodic poleward propagation dominates the internal variability.
- Indicates paper has been withdrawn from meeting
- Indicates an Award Winner