[Eoas-seminar] EOAS Colloquiuqm Speaker Fri Nov 8 3:30 Car 101

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Mon Nov 4 09:09:01 EST 2019

This week's EOAS Colloquium seminar on Friday at 3:30 in CAR 101 will be given by:

Dr. Alyssa Atwood  of EOAS at FSU

Is the concept of a zonally-averaged tropical precipitation change useful?

The response of the tropical atmosphere to forcing has been extensively studied through the lens of an energetic theory relating the zonal mean Hadley circulation to atmospheric energy transport across the equator. While this framework is useful for developing a conceptual understanding of the tropical atmosphere’s response to natural and anthropogenic forcing, by construction it averages out the rich zonal nature of atmospheric circulation and rainfall patterns, which reflect the distinct processes that govern large-scale precipitation in different regions of the tropics. In this talk, I will draw upon a large suite of future and paleoclimate model simulations to show that the zonal mean framework is generally not useful for characterizing shifts of the tropical rain belt at regional scales—regardless of the characteristics of the climate forcing. Under forcings with strong hemispheric asymmetry, the zonal mean shift is robust across models but the direction and magnitude of the shift varies strongly as a function of longitude. Under forcings with weak hemispheric asymmetry, zonal mean shifts are small or absent, but large regional shifts can occur that have important dynamical consequences. In addition, the precipitation response is highly sensitive to tropical mean state biases in models, highlighting an important caveat to interpreting rainfall changes from model simulations with poor representation of tropical rainfall climatology. I will discuss the implications of these findings for interpreting changes in the tropical rain belt from paleoclimate proxy records.

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