Observations show that the tropics has widened by about 2 to 5 degree latitudes since 1979 (Fu et al. 2006; Seidel et al. 2008). This widening and the concomitant poleward displacement of the subtropical dry zones may be accompanied by large-scale drying near 30oNand 30oS. It is found that the observed widening of the tropics in last three decades is significantly larger than the GCM simulated widening rates in the late twentieth century and the 21st century (e.g., Johanson and Fu 2009). In this talk, we will review recent progresses in the observational, modeling, and theoretical studies on the tropical expansion associated with the global climate change. New analyses of satellite observations and the comparison with model simulations will be presented to understand the discrepancy between the observed and simulated widening of the tropics. The implications of tropical expansion to regional climate change, hydrological cycles, and climate feedback will also be discussed.

Fu, Q., C.M. Johanson, J.M. Wallace, and T. Reichler, 2006: Enhanced mid-latitude tropospheric warming in satellite measurements. Science, 312, 1179.

Seidel, D.J., Q. Fu, W.J. Randel, T.J. Reichler, 2008: Widening of the tropical belt in a changing climate. Nature Geoscience, 1, 21-24.

Johanson, C.M., and Q. Fu, 2009: Hadley cell expansion: Model simulations versus observations. J. Clim., 22, 2713-2725.