Troposphere-Stratosphere Dynamics in Equatorial Waves and the MJO

In theoretical models of tropical dynamics, the effects of both surface friction and upward wave radiation through interaction with the stratosphere are oft-ignored, as they greatly complicate mathematical analysis. In this talk, we introduce surface drag and relax the rigid-lid assumption in a simple linear model of tropospheric dynamics in which convection strictly determines the vertical structure. It is shown through both theoretical and numerical analysis that the presence of a stratosphere dampens small scale waves, and that surface friction can excite the barotropic mode far away from the equator. In the second part of the talk, we use the linear model to understand if modulation of upward wave radiation by the stratosphere can explain how the Quasi Biennial Oscillation, a tropical stratospheric oscillating pattern of winds, can modulate the Madden Julian Oscillation (MJO), a large-scale oscillation of winds and precipitation in the tropics. It is shown that under linear dynamics, loss of energy to the stratosphere via upward wave radiation leads to dampened MJO growth rates under easterly winds, opposite of what is observed. Caveats and brief comments on cloud-radiative feedbacks are also discussed.

About this Series

The Atmosphere, Ocean and Climate Sack Lunch Seminar Series is an informal seminar series within PAOC that focuses on more specialized topics than the PAOC Colloquium. Seminar topics include all research concerning the science of atmosphere, ocean and climate. The seminars usually take place on Wednesdays from 12-1pm in 54-915. The presentations are either given by an invited speaker or by a member of PAOC and can focus on new research or discussion of a paper of particular interest.

Contact: sacklunch-committee@mit.edu for Zoom information