Lu, Deser & Reichler: Cause of the widening of the tropical belt since 1958

Geophysical Research Letters, 36, L03803; doi:10.1029/2008GL036076.

Cause of the widening of the tropical belt since 1958

Cause of the widening of the tropical belt since 1958

Jian Lu (Advanced Study Program, National Center for Atmospheric Research, Boulder, CO, USA; and Center for Ocean-Land-Atmosphere Studies, Calverton, MD, USA), Clara Deser (National Center for Atmospheric Research, Boulder, CO, USA), and Thomas Reichler (Department of Meteorology, University of Utah, Salt Lake City, UT, USA)

Abstract

Previous studies have shown that the width of the tropical belt has been increasing since at least the late 1970s based on a variety of metrics. One such metric, the frequency of occurrence of a high-altitude tropopause characteristic of the tropics, is used here to show that the observed widening of the tropics can be accurately replicated by an atmospheric general circulation model forced by the observed evolution of global SST and sea ice distributions as well as the direct radiative effects from both natural and anthropogenic sources. Contrasting this simulation with one forced by the observed SST and sea ice distributions alone reveals that the widening trend can be attributed entirely to direct radiative forcing, in particular those related to greenhouse gases and stratospheric ozone depletion. SST forcing causes no significant change in the width of the tropics, and even a contraction in some seasons.

(Received 22 September 2008, accepted 30 December 2008, published 5 February 2009.)

Lu, J., C. Deser, and T. Reichler (2009), Cause of the widening of the tropical belt since 1958, Geophys. Res. Lett., 36, L03803; doi:10.1029/2008GL036076.

Link to abstract: http://www.agu.org/pubs/crossref/2009/2008GL036076.shtml