Effective Isentropic Diffusivity of Tropospheric Transport
Tropospheric transport can be described qualitatively by the slow mean diabatic circulation and rapid isentropic mixing, yet a quantitative understanding of the transport circulation is complicated, as nearly half of the isentropic surfaces in the troposphere frequently intersect the ground. A theor...
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| Format: | Article |
| Language: | en_US |
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American Meteorological Society
2015
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| Online Access: | http://hdl.handle.net/1721.1/96339 https://orcid.org/0000-0002-6716-1576 |
| _version_ | 1811089633046429696 |
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| author | Chen, Gang Plumb, R. Alan |
| 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 Chen, Gang Plumb, R. Alan |
| author_sort | Chen, Gang |
| collection | MIT |
| description | Tropospheric transport can be described qualitatively by the slow mean diabatic circulation and rapid isentropic mixing, yet a quantitative understanding of the transport circulation is complicated, as nearly half of the isentropic surfaces in the troposphere frequently intersect the ground. A theoretical framework for the effective isentropic diffusivity of tropospheric transport is presented. Compared with previous isentropic analysis of effective diffusivity, a new diagnostic is introduced to quantify the eddy diffusivity of the near-surface isentropic flow. This diagnostic also links the effective eddy diffusivity directly to a diffusive closure of eddy fluxes through a finite-amplitude wave activity equation.
The theory is examined in a dry primitive equation model on the sphere. It is found that the upper troposphere is characterized by a diffusivity minimum at the jet’s center with enhanced mixing at the jet’s flanks and that the lower troposphere is dominated by stronger mixing throughout the baroclinic zone. This structure of isentropic diffusivity is generally consistent with the diffusivity obtained from the geostrophic component of the flow. Furthermore, the isentropic diffusivity agrees broadly with the tracer equivalent length obtained from either a spectral diffusion scheme or a semi-Lagrangian advection scheme, indicating that the effective diffusivity of tropospheric transport is largely dictated by large-scale stirring rather than details of the small-scale diffusion acting on the tracers. |
| first_indexed | 2024-09-23T14:22:18Z |
| format | Article |
| id | mit-1721.1/96339 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T14:22:18Z |
| publishDate | 2015 |
| publisher | American Meteorological Society |
| record_format | dspace |
| spelling | mit-1721.1/963392022-10-01T20:51:54Z Effective Isentropic Diffusivity of Tropospheric Transport Chen, Gang Plumb, R. Alan Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Massachusetts Institute of Technology. Program in Atmospheres, Oceans, and Climate Plumb, R. Alan Tropospheric transport can be described qualitatively by the slow mean diabatic circulation and rapid isentropic mixing, yet a quantitative understanding of the transport circulation is complicated, as nearly half of the isentropic surfaces in the troposphere frequently intersect the ground. A theoretical framework for the effective isentropic diffusivity of tropospheric transport is presented. Compared with previous isentropic analysis of effective diffusivity, a new diagnostic is introduced to quantify the eddy diffusivity of the near-surface isentropic flow. This diagnostic also links the effective eddy diffusivity directly to a diffusive closure of eddy fluxes through a finite-amplitude wave activity equation. The theory is examined in a dry primitive equation model on the sphere. It is found that the upper troposphere is characterized by a diffusivity minimum at the jet’s center with enhanced mixing at the jet’s flanks and that the lower troposphere is dominated by stronger mixing throughout the baroclinic zone. This structure of isentropic diffusivity is generally consistent with the diffusivity obtained from the geostrophic component of the flow. Furthermore, the isentropic diffusivity agrees broadly with the tracer equivalent length obtained from either a spectral diffusion scheme or a semi-Lagrangian advection scheme, indicating that the effective diffusivity of tropospheric transport is largely dictated by large-scale stirring rather than details of the small-scale diffusion acting on the tracers. 2015-04-02T17:18:06Z 2015-04-02T17:18:06Z 2014-09 2014-05 Article http://purl.org/eprint/type/JournalArticle 0022-4928 1520-0469 http://hdl.handle.net/1721.1/96339 Chen, Gang, and Alan Plumb. “Effective Isentropic Diffusivity of Tropospheric Transport.” J. Atmos. Sci. 71, no. 9 (September 2014): 3499–3520. © 2014 American Meteorological Society https://orcid.org/0000-0002-6716-1576 en_US http://dx.doi.org/10.1175/jas-d-13-0333.1 Journal of the Atmospheric Sciences 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 |
| spellingShingle | Chen, Gang Plumb, R. Alan Effective Isentropic Diffusivity of Tropospheric Transport |
| title | Effective Isentropic Diffusivity of Tropospheric Transport |
| title_full | Effective Isentropic Diffusivity of Tropospheric Transport |
| title_fullStr | Effective Isentropic Diffusivity of Tropospheric Transport |
| title_full_unstemmed | Effective Isentropic Diffusivity of Tropospheric Transport |
| title_short | Effective Isentropic Diffusivity of Tropospheric Transport |
| title_sort | effective isentropic diffusivity of tropospheric transport |
| url | http://hdl.handle.net/1721.1/96339 https://orcid.org/0000-0002-6716-1576 |
| work_keys_str_mv | AT chengang effectiveisentropicdiffusivityoftropospherictransport AT plumbralan effectiveisentropicdiffusivityoftropospherictransport |