Relative humidity changes in a warmer climate
Key climate feedback due to water vapor and clouds rest largely on how relative humidity R changes in a warmer climate, yet this has not been extensively analyzed in models. General circulation models (GCMs) from the CMIP3 archive and several higherresolution atmospheric GCMs examined here genera...
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| Format: | Article |
| Language: | en_US |
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American Geophysical Union
2011
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| Online Access: | http://hdl.handle.net/1721.1/64661 https://orcid.org/0000-0003-1748-0816 |
| _version_ | 1811075867751743488 |
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| author | Sherwood, Steven C. Ingram, William Tsushima, Yoko Satoh, Masaki Roberts, Malcolm Vidale, Pier Luigi 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 Sherwood, Steven C. Ingram, William Tsushima, Yoko Satoh, Masaki Roberts, Malcolm Vidale, Pier Luigi O'Gorman, Paul |
| author_sort | Sherwood, Steven C. |
| collection | MIT |
| description | Key climate feedback due to water vapor and clouds rest largely on how relative
humidity R changes in a warmer climate, yet this has not been extensively analyzed in
models. General circulation models (GCMs) from the CMIP3 archive and several higherresolution
atmospheric GCMs examined here generally predict a characteristic pattern
of R trend with global temperature that has been reported previously in individual models,
including increase around the tropopause, decrease in the tropical upper troposphere,
and decrease in midlatitudes. This pattern is very similar to that previously reported for
cloud cover in the same GCMs, confirming the role of R in controlling changes in
simulated cloud. Comparing different models, the trend in each part of the troposphere is
approximately proportional to the upward and/or poleward gradient of R in the present
climate. While this suggests that the changes simply reflect a shift of the R pattern upward
with the tropopause and poleward with the zonal jets, the drying trend in the subtropics is
roughly 3 times too large to be attributable to shifts of subtropical features, and the
subtropical R minima deepen in most models. R trends are correlated with horizontal
model resolution, especially outside the tropics, where they show signs of convergence and
latitudinal gradients become close to available observations for GCM resolutions near
T85 and higher. We argue that much of the systematic change in R can be explained by
the local specific humidity having been set (by condensation) in remote regions with
different temperature changes, hence the gradients and trends each depend on a model’s
ability to resolve moisture transport. Finally, subtropical drying trends predicted from the
warming alone fall well short of those observed in recent decades. While this discrepancy
supports previous reports of GCMs underestimating Hadley cell expansion, our results
imply that shifts alone are not a sufficient interpretation of changes. |
| first_indexed | 2024-09-23T10:13:03Z |
| format | Article |
| id | mit-1721.1/64661 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T10:13:03Z |
| publishDate | 2011 |
| publisher | American Geophysical Union |
| record_format | dspace |
| spelling | mit-1721.1/646612024-05-15T02:21:33Z Relative humidity changes in a warmer climate Sherwood, Steven C. Ingram, William Tsushima, Yoko Satoh, Masaki Roberts, Malcolm Vidale, Pier Luigi O'Gorman, Paul Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences O'Gorman, Paul Ambrose O'Gorman, Paul Ambrose Key climate feedback due to water vapor and clouds rest largely on how relative humidity R changes in a warmer climate, yet this has not been extensively analyzed in models. General circulation models (GCMs) from the CMIP3 archive and several higherresolution atmospheric GCMs examined here generally predict a characteristic pattern of R trend with global temperature that has been reported previously in individual models, including increase around the tropopause, decrease in the tropical upper troposphere, and decrease in midlatitudes. This pattern is very similar to that previously reported for cloud cover in the same GCMs, confirming the role of R in controlling changes in simulated cloud. Comparing different models, the trend in each part of the troposphere is approximately proportional to the upward and/or poleward gradient of R in the present climate. While this suggests that the changes simply reflect a shift of the R pattern upward with the tropopause and poleward with the zonal jets, the drying trend in the subtropics is roughly 3 times too large to be attributable to shifts of subtropical features, and the subtropical R minima deepen in most models. R trends are correlated with horizontal model resolution, especially outside the tropics, where they show signs of convergence and latitudinal gradients become close to available observations for GCM resolutions near T85 and higher. We argue that much of the systematic change in R can be explained by the local specific humidity having been set (by condensation) in remote regions with different temperature changes, hence the gradients and trends each depend on a model’s ability to resolve moisture transport. Finally, subtropical drying trends predicted from the warming alone fall well short of those observed in recent decades. While this discrepancy supports previous reports of GCMs underestimating Hadley cell expansion, our results imply that shifts alone are not a sufficient interpretation of changes. National Science Foundation (U.S.) (grant ATM-0453639) 2011-06-22T21:31:36Z 2011-06-22T21:31:36Z 2010-05 2009-06 Article http://purl.org/eprint/type/JournalArticle 0148–0227 http://hdl.handle.net/1721.1/64661 Sherwood, S. C., W. Ingram, Y. Tsushima, M. Satoh, M. Roberts, P. L. Vidale, and P. A. O'Gorman (2010), Relative humidity changes in a warmer climate, J. Geophys. Res., 115, D09104, doi:10.1029/2009JD012585 ©2010 American Geophysical Union https://orcid.org/0000-0003-1748-0816 en_US http://dx.doi.org/10.1029/2009JD012585 Journal of Geophysical Research 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 Geophysical Union Prof. O'Gorman via Chris Sherratt |
| spellingShingle | Sherwood, Steven C. Ingram, William Tsushima, Yoko Satoh, Masaki Roberts, Malcolm Vidale, Pier Luigi O'Gorman, Paul Relative humidity changes in a warmer climate |
| title | Relative humidity changes in a warmer climate |
| title_full | Relative humidity changes in a warmer climate |
| title_fullStr | Relative humidity changes in a warmer climate |
| title_full_unstemmed | Relative humidity changes in a warmer climate |
| title_short | Relative humidity changes in a warmer climate |
| title_sort | relative humidity changes in a warmer climate |
| url | http://hdl.handle.net/1721.1/64661 https://orcid.org/0000-0003-1748-0816 |
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