Tropical Cyclogenesis Sensitivity to Environmental Parameters in Radiative-Convective Equilibrium
In this study, the relationship between the likelihood of tropical cyclogenesis and external environmental forcings is explored in the simplest idealized modelling framework possible: radiative-convective equilibrium on a doubly periodic f-plane. In such an environment, control of the equilibrium en...
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| Format: | Article |
| Language: | en_US |
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Wiley Blackwell
2012
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| Online Access: | http://hdl.handle.net/1721.1/75765 https://orcid.org/0000-0002-2066-2082 |
| _version_ | 1826198672823549952 |
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| author | Nolan, David S. Rappin, Eric D. Emanuel, Kerry Andrew |
| 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 Nolan, David S. Rappin, Eric D. Emanuel, Kerry Andrew |
| author_sort | Nolan, David S. |
| collection | MIT |
| description | In this study, the relationship between the likelihood of tropical cyclogenesis and external environmental forcings is explored in the simplest idealized modelling framework possible: radiative-convective equilibrium on a doubly periodic f-plane. In such an environment, control of the equilibrium environmental sounding is reduced to three parameters: the sea-surface temperature, the Coriolis parameter, and the imposed background surface wind speed. Cloud-resolving mesoscale model simulations are used to generate environments of radiative-convective equilibrium determined by these three factors. The favourability of these environments for tropical cyclogenesis is measured in three ways: in terms of the maximum potential intensity (MPI) of the sounding, based on the thermodynamic theory of Emanuel; in terms of the ‘genesis potential’ determined by an empirical genesis parameter; and in terms of the propensity of weak initial vortices in these environments to form into tropical cyclones.
The simulated environments of radiative—convective equilibrium with no vertical wind shear are found to be very favourable for tropical cyclogenesis. Weak initial vortices always transition to a tropical cyclone, even for rather low sea-surface temperatures. However, the time required for these vortices to make the transition from a weak, mid-level vortex to a rapidly developing tropical cyclone decreases as the MPI increases, indicating the importance of MPI in enhancing the frequency of cyclogenesis. The relationship between this ‘time to genesis’ and the thermodynamic parameters is explored. The time to genesis is found to be very highly (negatively) correlated to MPI, with little or no relationship to convective instability, Coriolis parameter, mid-level humidity, or the empirical genesis parameter.
In some cases, tropical cyclones are found to form spontaneously from random convection. This formation is due to a cooperative interaction between large-scale moisture, long-wave radiation, and locally enhanced sea-surface fluxes, similar to the ‘aggregation’ of convection found in previous studies. |
| first_indexed | 2024-09-23T11:08:02Z |
| format | Article |
| id | mit-1721.1/75765 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T11:08:02Z |
| publishDate | 2012 |
| publisher | Wiley Blackwell |
| record_format | dspace |
| spelling | mit-1721.1/757652022-09-27T17:22:02Z Tropical Cyclogenesis Sensitivity to Environmental Parameters in Radiative-Convective Equilibrium Nolan, David S. Rappin, Eric D. Emanuel, Kerry Andrew Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Massachusetts Institute of Technology. Program in Atmospheres, Oceans, and Climate Emanuel, Kerry Emanuel, Kerry Andrew In this study, the relationship between the likelihood of tropical cyclogenesis and external environmental forcings is explored in the simplest idealized modelling framework possible: radiative-convective equilibrium on a doubly periodic f-plane. In such an environment, control of the equilibrium environmental sounding is reduced to three parameters: the sea-surface temperature, the Coriolis parameter, and the imposed background surface wind speed. Cloud-resolving mesoscale model simulations are used to generate environments of radiative-convective equilibrium determined by these three factors. The favourability of these environments for tropical cyclogenesis is measured in three ways: in terms of the maximum potential intensity (MPI) of the sounding, based on the thermodynamic theory of Emanuel; in terms of the ‘genesis potential’ determined by an empirical genesis parameter; and in terms of the propensity of weak initial vortices in these environments to form into tropical cyclones. The simulated environments of radiative—convective equilibrium with no vertical wind shear are found to be very favourable for tropical cyclogenesis. Weak initial vortices always transition to a tropical cyclone, even for rather low sea-surface temperatures. However, the time required for these vortices to make the transition from a weak, mid-level vortex to a rapidly developing tropical cyclone decreases as the MPI increases, indicating the importance of MPI in enhancing the frequency of cyclogenesis. The relationship between this ‘time to genesis’ and the thermodynamic parameters is explored. The time to genesis is found to be very highly (negatively) correlated to MPI, with little or no relationship to convective instability, Coriolis parameter, mid-level humidity, or the empirical genesis parameter. In some cases, tropical cyclones are found to form spontaneously from random convection. This formation is due to a cooperative interaction between large-scale moisture, long-wave radiation, and locally enhanced sea-surface fluxes, similar to the ‘aggregation’ of convection found in previous studies. National Science Foundation (U.S.) (Grant ATM-0432067) 2012-12-18T16:18:15Z 2012-12-18T16:18:15Z 2007-12 Article http://purl.org/eprint/type/JournalArticle 0035-9009 1477-870X http://hdl.handle.net/1721.1/75765 Nolan, David S., Eric D. Rappin, and Kerry A. Emanuel. “Tropical Cyclogenesis Sensitivity to Environmental Parameters in Radiative-convective Equilibrium.” Quarterly Journal of the Royal Meteorological Society 133.629 (2007): 2085–2107. https://orcid.org/0000-0002-2066-2082 en_US http://dx.doi.org/10.1002/qj.170 Quarterly Journal of the Royal Meteorological Society 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 Wiley Blackwell Prof. Emanuel via Chris Sherratt |
| spellingShingle | Nolan, David S. Rappin, Eric D. Emanuel, Kerry Andrew Tropical Cyclogenesis Sensitivity to Environmental Parameters in Radiative-Convective Equilibrium |
| title | Tropical Cyclogenesis Sensitivity to Environmental Parameters in Radiative-Convective Equilibrium |
| title_full | Tropical Cyclogenesis Sensitivity to Environmental Parameters in Radiative-Convective Equilibrium |
| title_fullStr | Tropical Cyclogenesis Sensitivity to Environmental Parameters in Radiative-Convective Equilibrium |
| title_full_unstemmed | Tropical Cyclogenesis Sensitivity to Environmental Parameters in Radiative-Convective Equilibrium |
| title_short | Tropical Cyclogenesis Sensitivity to Environmental Parameters in Radiative-Convective Equilibrium |
| title_sort | tropical cyclogenesis sensitivity to environmental parameters in radiative convective equilibrium |
| url | http://hdl.handle.net/1721.1/75765 https://orcid.org/0000-0002-2066-2082 |
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