We thank Simona Bordoni, Isaac Held, Yohai Kaspi, Xavier Levine, and Paul O’Gorman for helpful discussions and technical assistance. The comments of two anonymous reviewers helped clarify the presentation of our work. This work was supported by a National Defense Science and Engineering Graduate Fellowship, a National Science Foundation Graduate Research Fellowship, and a David and Lucile Packard Fellowship. The GCM simulations were performed on Caltech’s Division of Geological and Planetary Sciences Dell cluster. The program code for the simulations, based on the Flexible Modeling System of the Geophysical Fluid Dynamics Laboratory, as well as the simulation results themselves are available from the authors upon request.
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We are not suggesting that this scaling holds in general [see, e.g., O’Gorman and Schneider (2008b) and our Fig. 6 for a counterexample in the global mean] but only for the zonal difference in the tropics.
All figures show psDσ/Dt, which differs only slightly (~0.1% in the region of interest) from Dp/Dt as σDps/Dt is small.