Moist Formulations of the Eliassen–Palm Flux and Their Connection to the Surface Westerlies
Name
Moist formulations of the eliassen.pdf
Size
3.62 MB
Format
Adobe PDF
Checksum (MD5)
0290b48900cf3bbde99e70b408564120
Author(s)
Dwyer, John G
O'Gorman, Paul
Date Issued
January 2017
Journal
Journal of the Atmospheric Sciences
Publisher
American Meteorological Society
Citation
Dwyer, John G., and O’Gorman, Paul A. “Moist Formulations of the Eliassen–Palm Flux and Their Connection to the Surface Westerlies.” Journal of the Atmospheric Sciences 74, 2 (February 2017): 513–530 © 2017 American Meteorological Society
Version
Final published version
Abstract
The Eliassen–Palm (EP) flux is an important diagnostic for wave propagation and wave–mean flow interaction in the atmosphere. Here, two moist formulations of the EP flux are compared with the traditional dry EP flux, and their links to the surface westerlies are analyzed using reanalysis data and simulations with GCMs. The first moist formulation of the EP flux modifies only the static stability to account for latent heat release by eddies, while the second moist formulation simply replaces all potential temperatures with equivalent potential temperatures. For reanalysis data, the peak upward EP flux in the lower troposphere is farther equatorward and stronger when the moist formulations are used, with greater changes for the second moist formulation. The moist formulations have the advantage of giving a closer relationship over the seasonal cycle between the latitudes of the peak surface westerlies and the peak upward EP flux. In simulations with a comprehensive GCM, the dry and moist upward EP fluxes shift poleward by a similar amount as the climate warms. In simulations over a wider range of climates with an idealized GCM, the surface westerlies can shift both poleward and equatorward with warming, and they are influenced by an anomalous region of dry EP flux divergence near the subtropical jet. Using moist EP fluxes weakens this anomalous divergence in the idealized GCM simulations, and the shifts in the surface westerlies can then be understood through changes in the preference for equatorward or poleward wave propagation.
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
Terms of Use
Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1175/jas-d-16-0111.1
