Tropical drying trends in global warming models and observations

J. David Neelin, Matthias Munnich, Hui Su, Joyce E. Meyerson, and Christopher E. Holloway, 2006:
Proc. Nat. Acd. Sci., 103, 6110-6115.
·Paper (PDF 1.6 MB)
·Supporting Information (PDF 564 KB)
© Copyright 2006 by the National Academy of Sciences.

Abstract. Anthropogenic changes in tropical rainfall are evaluated in a multi-model ensemble of global warming simulations. Major discrepancies on the spatial distribution of these precipitation changes remain in the latest generation models analyzed here. Despite this, we find a number of measures, both global and local, on which reasonable agreement is obtained, notably for the regions of drying trend (negative precipitation anomalies). Models agree on the overall amplitude of the precipitation decreases that occur at the margins of the convective zones, with percent error bars of magnitude similar to those for the tropical warming. Similar agreement is found on a precipitation climate sensitivity defined here, and on differential moisture increase inside and outside convection zones, a step in a hypothesized causal path leading to precipitation changes. A measure of local inter-model agreement on significant trends indicates consistent predictions for particular regions. Observed rainfall trends in several data sets show a significant summer drying trend in a main region of inter-model agreement: the Caribbean/Central-American region.

Research Highlight Page

Acknowledgments. This work was supported under National Science Foundation grant ATM-0082529 and National Oceanic and Atmospheric Administration grants NA04OAR4310013 and NA05OAR4310007. We acknowledge the modeling groups for providing their data, PCMDI at Lawrence Livermore National Laboratories for collecting the model data, the JSC/CLIVAR Working Group on Coupled Modelling (WGCM) for organizing the model analysis activity, and the IPCC WG1 TSU for technical support. The IPCC Data Archive at Lawrence Livermore National Laboratory is supported by the Office of Science, U.S. Department of Energy. The observed precipitation data sets are supported by the National Oceanographic and Atmospheric Administration and by a joint project of the German Weather Service (Global Precipitation Climatology Centre) and the Johann Wolfgang Goethe-University Frankfurt (Institute for Atmosphere and Environment Working Group for Climatology).