Increase in the skewness of extratropical vertical velocities with climate warming: fully nonlinear simulations versus moist baroclinic instability
Name
ogorman_qjrms_2018.pdf
Size
657.44 KB
Format
Adobe PDF
Checksum (MD5)
22c18969e2c851d07b5662e0ad9a6884
Author(s)
Merlis, Timothy M.
Singh, Martin S.
O'Gorman, Paul
Date Issued
November 2017
Journal
Quarterly Journal of the Royal Meteorological Society
Publisher
Wiley Blackwell
Citation
O’Gorman, Paul A., Timothy M. Merlis, and Martin S. Singh. “Increase in the Skewness of Extratropical Vertical Velocities with Climate Warming: Fully Nonlinear Simulations Versus Moist Baroclinic Instability.” Quarterly Journal of the Royal Meteorological Society 144, no. 710 (December 27, 2017): 208–217.
Version
Author's final manuscript
Abstract
The distribution of vertical velocities in the extratropical troposphere is skewed such that upward motions are faster than downward motions. This skewness is important for the intensity distribution of precipitation and for the effective static stability experienced by moist eddies. We show here that the skewness of the vertical velocity increases in magnitude as the climate warms in simulations with an idealized general circulation model (GCM), except in very warm climates. That the skewness increases with warming is consistent with studies of moist baroclinic instability which suggest that the area of updraughts should contract as the stratification approaches moist neutrality in warm climates. However, the increase in skewness with warming is much weaker in the fully nonlinear simulations as compared to what is found for unstable modes of moist baroclinic instability in the same GCM. Nonlinear equilibration to a macroturbulent state leads to a reduction in skewness in warm climates. Therefore, while the unstable modes may be relevant for some cases of cyclogenesis, they overestimate the effect of warming on the skewness of the overall distribution of the vertical velocity. Remarkably, the most unstable mode transitions from a quasi‐periodic wave to an isolated diabatic Rossby vortex at sufficiently high temperatures, with possible implications for fast‐growing disturbances in warm climates. Keywords: skewness, vertical velocity, non‐Gaussian,moist baroclinic instability, diabatic Rossby vortex, diabatic Rossby wave, effective static stability, climate change
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
Terms of Use
Creative Commons Attribution-Noncommercial-Share Alike
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1002/qj.3195
