Increase in the skewness of extratropical vertical velocities with climate warming: fully nonlinear simulations versus moist baroclinic instability
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 th...
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| Format: | Article |
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Wiley Blackwell
2019
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| Online Access: | http://hdl.handle.net/1721.1/119853 https://orcid.org/0000-0003-1748-0816 |
| _version_ | 1826206457297633280 |
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| author | Merlis, Timothy M. Singh, Martin S. O'Gorman, Paul |
| author2 | Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences |
| author_facet | Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Merlis, Timothy M. Singh, Martin S. O'Gorman, Paul |
| author_sort | Merlis, Timothy M. |
| collection | MIT |
| description | 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 |
| first_indexed | 2024-09-23T13:31:03Z |
| format | Article |
| id | mit-1721.1/119853 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T13:31:03Z |
| publishDate | 2019 |
| publisher | Wiley Blackwell |
| record_format | dspace |
| spelling | mit-1721.1/1198532022-10-01T15:38:33Z Increase in the skewness of extratropical vertical velocities with climate warming: fully nonlinear simulations versus moist baroclinic instability Merlis, Timothy M. Singh, Martin S. O'Gorman, Paul Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences O'Gorman, Paul O'Gorman, Paul 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 National Science Foundation (U.S.) (Grant AGS 1148594) 2019-01-04T16:00:57Z 2019-01-04T16:00:57Z 2017-11 2017-09 Article http://purl.org/eprint/type/JournalArticle 0035-9009 http://hdl.handle.net/1721.1/119853 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. https://orcid.org/0000-0003-1748-0816 en_US https://doi.org/10.1002/qj.3195 Quarterly Journal of the Royal Meteorological Society Creative Commons Attribution-Noncommercial-Share Alike http://creativecommons.org/licenses/by-nc-sa/4.0/ application/pdf Wiley Blackwell Prof. O'Gorman via Chris Sherrstt |
| spellingShingle | Merlis, Timothy M. Singh, Martin S. O'Gorman, Paul Increase in the skewness of extratropical vertical velocities with climate warming: fully nonlinear simulations versus moist baroclinic instability |
| title | Increase in the skewness of extratropical vertical velocities with climate warming: fully nonlinear simulations versus moist baroclinic instability |
| title_full | Increase in the skewness of extratropical vertical velocities with climate warming: fully nonlinear simulations versus moist baroclinic instability |
| title_fullStr | Increase in the skewness of extratropical vertical velocities with climate warming: fully nonlinear simulations versus moist baroclinic instability |
| title_full_unstemmed | Increase in the skewness of extratropical vertical velocities with climate warming: fully nonlinear simulations versus moist baroclinic instability |
| title_short | Increase in the skewness of extratropical vertical velocities with climate warming: fully nonlinear simulations versus moist baroclinic instability |
| title_sort | increase in the skewness of extratropical vertical velocities with climate warming fully nonlinear simulations versus moist baroclinic instability |
| url | http://hdl.handle.net/1721.1/119853 https://orcid.org/0000-0003-1748-0816 |
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