Long-lasting Midlatitude Response to Short-lived Tropical Heating Events

Abstract:

The midlatitude response to localized equatorial heating events that last 2 days is examined through experimentation with an atmospheric general circulation model. Such responses are argued to be important because many tropical rainfall events only last a short time and because the responses to such pulses serve as building blocks with which to study the impacts of more general heating fluctuations. The experiments indicate that pulse heating produces responses in midlatitude locations that are far from the source and these responses persist much longer than the heating pulses that drive them. Moreover the responses have little or no phase propagation. Consequently the upper tropospheric structure of the responses is remarkably similar to the reaction to steady tropical heating, including being composed of similar recurring patterns and being especially pronounced at special locations. The impact of short-lived tropical heating also produces persistent responses in midlatitude surface fields and in the statistics of synoptic eddies.

These results imply a) there is potential for improving subseasonal prediction through improved assimilation and short range forecasts of tropical precipitation and b) attributing subseasonal midlatitude events to tropical heating is more difficult than it may at first appear to be.