Abstract
Climate models simulate a weakening of the Walker circulation in response to increased greenhouse gases, but it has not been possible to detect this weakening with observations because there are not direct measurements of atmospheric circulation strength. Indirect measurements, such as equatorial gradients in sea level pressure (SLP), exhibit trends of inconsistent sign. In this study we estimate the change in midtropospheric velocity (ω500) from observed change in cloud cover, which we argue is more closely tied to the overturning circulation than indirect measurements of SLP at the surface. Our estimates suggest a weakening and eastward shift of the Walker circulation over the last century. Because changes in cloud cover in Atmospheric Model Intercomparison Project simulations forced with increased sea surface temperature are remarkably similar in pattern, sign, and magnitude, we assert that the observed changes in cloud cover and the associated weakening of Walker circulation are at least in part externally forced.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 7758-7766 |
| Number of pages | 9 |
| Journal | Geophysical Research Letters |
| Volume | 42 |
| Issue number | 18 |
| DOIs | |
| State | Published - Sep 28 2015 |
Fingerprint
Keywords
- cloud cover
- Walker circulation
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Geophysics
Cite this
Evidence for weakening of the Walker circulation from cloud observations. / Bellomo, Katinka; Clement, Amy C.
In: Geophysical Research Letters, Vol. 42, No. 18, 28.09.2015, p. 7758-7766.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Evidence for weakening of the Walker circulation from cloud observations
AU - Bellomo, Katinka
AU - Clement, Amy C
PY - 2015/9/28
Y1 - 2015/9/28
N2 - Climate models simulate a weakening of the Walker circulation in response to increased greenhouse gases, but it has not been possible to detect this weakening with observations because there are not direct measurements of atmospheric circulation strength. Indirect measurements, such as equatorial gradients in sea level pressure (SLP), exhibit trends of inconsistent sign. In this study we estimate the change in midtropospheric velocity (ω500) from observed change in cloud cover, which we argue is more closely tied to the overturning circulation than indirect measurements of SLP at the surface. Our estimates suggest a weakening and eastward shift of the Walker circulation over the last century. Because changes in cloud cover in Atmospheric Model Intercomparison Project simulations forced with increased sea surface temperature are remarkably similar in pattern, sign, and magnitude, we assert that the observed changes in cloud cover and the associated weakening of Walker circulation are at least in part externally forced.
AB - Climate models simulate a weakening of the Walker circulation in response to increased greenhouse gases, but it has not been possible to detect this weakening with observations because there are not direct measurements of atmospheric circulation strength. Indirect measurements, such as equatorial gradients in sea level pressure (SLP), exhibit trends of inconsistent sign. In this study we estimate the change in midtropospheric velocity (ω500) from observed change in cloud cover, which we argue is more closely tied to the overturning circulation than indirect measurements of SLP at the surface. Our estimates suggest a weakening and eastward shift of the Walker circulation over the last century. Because changes in cloud cover in Atmospheric Model Intercomparison Project simulations forced with increased sea surface temperature are remarkably similar in pattern, sign, and magnitude, we assert that the observed changes in cloud cover and the associated weakening of Walker circulation are at least in part externally forced.
KW - cloud cover
KW - Walker circulation
UR - http://www.scopus.com/inward/record.url?scp=84945208046&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84945208046&partnerID=8YFLogxK
U2 - 10.1002/2015GL065463
DO - 10.1002/2015GL065463
M3 - Article
AN - SCOPUS:84945208046
VL - 42
SP - 7758
EP - 7766
JO - Geophysical Research Letters
JF - Geophysical Research Letters
SN - 0094-8276
IS - 18
ER -