A Weak Temperature Gradient Framework to Quantify the Causes of Potential Intensity Variability in the Tropics
<jats:title>Abstract</jats:title><jats:p>Potential intensity (PI) has been shown to have a linear sensitivity to sea surface temperature (SST) of about 8 m s<jats:sup>−1</jats:sup> K<jats:sup>−1</jats:sup>, which is close to the sensitivity of PI in simulati...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
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American Meteorological Society
2023
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| Online Access: | https://hdl.handle.net/1721.1/147976 |
| _version_ | 1826203839807619072 |
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| author | Rousseau-Rizzi, Raphaël Emanuel, Kerry |
| 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 Rousseau-Rizzi, Raphaël Emanuel, Kerry |
| author_sort | Rousseau-Rizzi, Raphaël |
| collection | MIT |
| description | <jats:title>Abstract</jats:title><jats:p>Potential intensity (PI) has been shown to have a linear sensitivity to sea surface temperature (SST) of about 8 m s<jats:sup>−1</jats:sup> K<jats:sup>−1</jats:sup>, which is close to the sensitivity of PI in simulations subject to a weak temperature gradient (WTG) approximation. This suggests that most of the PI variance is associated with local rather than global SST variations. We verify that PI perturbations are approximately linear in SST, with slopes of 1.8 ± 0.2 m s<jats:sup>−1</jats:sup> K<jats:sup>−1</jats:sup> in radiative–convective equilibrium (RCE) and 9.1 ± 0.9 m s<jats:sup>−1</jats:sup> K<jats:sup>−1</jats:sup> in WTG. To do so, we simulate the sensitivity of both RCE and WTG states in a single-column model (SCM) perturbed by changing in turn CO<jats:sub>2</jats:sub> concentration, aerosol concentrations, prescribed SST, and surface winds speeds. While PI is much more sensitive to SST in WTG than in RCE simulations, the SST itself is much less sensitive to radiative forcing in WTG than in RCE because of the absence of strong atmospheric response. Using these results, we develop a linear model, based on SST and midlevel saturation MSE perturbations, to partition SST and PI perturbations between local components occurring under a WTG constraint and global components that are representative of an RCE state. This model explains up to 95% of the variability of PI in reanalysis. The SCM-derived linear model coefficients are statistically indistinguishable from coefficients from a linear fit of reanalysis PI to SST and midlevel saturation MSE in most ocean basins. Our model shows that North Atlantic PI variations are explained almost entirely by local forcings in recent decades.</jats:p> |
| first_indexed | 2024-09-23T12:44:02Z |
| format | Article |
| id | mit-1721.1/147976 |
| institution | Massachusetts Institute of Technology |
| language | English |
| last_indexed | 2024-09-23T12:44:02Z |
| publishDate | 2023 |
| publisher | American Meteorological Society |
| record_format | dspace |
| spelling | mit-1721.1/1479762023-02-09T03:26:45Z A Weak Temperature Gradient Framework to Quantify the Causes of Potential Intensity Variability in the Tropics Rousseau-Rizzi, Raphaël Emanuel, Kerry Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences <jats:title>Abstract</jats:title><jats:p>Potential intensity (PI) has been shown to have a linear sensitivity to sea surface temperature (SST) of about 8 m s<jats:sup>−1</jats:sup> K<jats:sup>−1</jats:sup>, which is close to the sensitivity of PI in simulations subject to a weak temperature gradient (WTG) approximation. This suggests that most of the PI variance is associated with local rather than global SST variations. We verify that PI perturbations are approximately linear in SST, with slopes of 1.8 ± 0.2 m s<jats:sup>−1</jats:sup> K<jats:sup>−1</jats:sup> in radiative–convective equilibrium (RCE) and 9.1 ± 0.9 m s<jats:sup>−1</jats:sup> K<jats:sup>−1</jats:sup> in WTG. To do so, we simulate the sensitivity of both RCE and WTG states in a single-column model (SCM) perturbed by changing in turn CO<jats:sub>2</jats:sub> concentration, aerosol concentrations, prescribed SST, and surface winds speeds. While PI is much more sensitive to SST in WTG than in RCE simulations, the SST itself is much less sensitive to radiative forcing in WTG than in RCE because of the absence of strong atmospheric response. Using these results, we develop a linear model, based on SST and midlevel saturation MSE perturbations, to partition SST and PI perturbations between local components occurring under a WTG constraint and global components that are representative of an RCE state. This model explains up to 95% of the variability of PI in reanalysis. The SCM-derived linear model coefficients are statistically indistinguishable from coefficients from a linear fit of reanalysis PI to SST and midlevel saturation MSE in most ocean basins. Our model shows that North Atlantic PI variations are explained almost entirely by local forcings in recent decades.</jats:p> 2023-02-08T17:53:16Z 2023-02-08T17:53:16Z 2021 2023-02-08T17:19:40Z Article http://purl.org/eprint/type/JournalArticle https://hdl.handle.net/1721.1/147976 Rousseau-Rizzi, Raphaël and Emanuel, Kerry. 2021. "A Weak Temperature Gradient Framework to Quantify the Causes of Potential Intensity Variability in the Tropics." Journal of Climate, 34 (21). en 10.1175/JCLI-D-21-0139.1 Journal of Climate 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. application/pdf American Meteorological Society American Meteorological Society (AMS) |
| spellingShingle | Rousseau-Rizzi, Raphaël Emanuel, Kerry A Weak Temperature Gradient Framework to Quantify the Causes of Potential Intensity Variability in the Tropics |
| title | A Weak Temperature Gradient Framework to Quantify the Causes of Potential Intensity Variability in the Tropics |
| title_full | A Weak Temperature Gradient Framework to Quantify the Causes of Potential Intensity Variability in the Tropics |
| title_fullStr | A Weak Temperature Gradient Framework to Quantify the Causes of Potential Intensity Variability in the Tropics |
| title_full_unstemmed | A Weak Temperature Gradient Framework to Quantify the Causes of Potential Intensity Variability in the Tropics |
| title_short | A Weak Temperature Gradient Framework to Quantify the Causes of Potential Intensity Variability in the Tropics |
| title_sort | weak temperature gradient framework to quantify the causes of potential intensity variability in the tropics |
| url | https://hdl.handle.net/1721.1/147976 |
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