A radiative-convective equilibrium perspective of weakening of the tropical walker circulation in response to global warming

Xianglei Huang, Hui Wen Chuang, Andrew Dessler, Xiuhong Chen, Kenneth Minschwaner, Yi Ming, V. Ramaswamy

Research output: Contribution to journalArticle

4 Scopus citations

Abstract

Both observational analysis andGCMsimulations indicate that the tropical Walker circulation is becoming weaker and may continue to weaken as a consequence of climate change. Here, the authors use a conceptual radiative-convective equilibrium (RCE) framework to interpret the weakening of the Walker circulation as simulated by the GFDL coupled GCM. Based on the modeled lapse rate and clear-sky cooling rate profiles, the RCE framework can directly compute the change of vertical velocity in the descending branch of the Walker circulation, which agrees with the counterpart simulated by the GFDL model. The results show that the vertical structure of clear-sky radiative cooling rate QR will change in response to the increased water vapor as the globe warms. The authors explain why the change of QR is positive in the uppermost part of the troposphere (<300 hPa) and is negative for the rest of the troposphere. As a result, both the change of clearsky cooling rate and the change of tropospheric lapse rate contribute to the weakening of circulation. The vertical velocity changes due to the two factors are comparable to each other from the top of the planetary boundary layer to 600 hPa. From 600 to 300 hPa lapse rate changes are the dominant cause of the weakening circulation. Above 300 hPa, the change due to QR is opposite to the change due to lapse rate, which forces a slight increase in vertical velocity that is seen in the model simulation.

Original languageEnglish (US)
Pages (from-to)1643-1653
Number of pages11
JournalJournal of Climate
Volume26
Issue number5
DOIs
StatePublished - Mar 1 2013
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Atmospheric Science

Keywords

  • Climate change
  • Climate models
  • Longwave radiation
  • Radiative-convective equilibrium
  • Walker circulation

Fingerprint Dive into the research topics of 'A radiative-convective equilibrium perspective of weakening of the tropical walker circulation in response to global warming'. Together they form a unique fingerprint.

Cite this