Australia: The Land Where Time Began

A biography of the Australian continent 

Southern Hemisphere Hadley Cell, Expansion in Response to Forcing by Greenhouse Gas

In this paper Nguyen et al. investigated changes to the Southern Hemisphere Hadley Cell over the 20^th century by using the Twentieth Century Reanalysis (20CR) and coupled model simulations from phase 5 of the Coupled Model Intercomparison Project (SMIP5). Trends computed on a 30-yr sliding window on the 20CR dataset revealed that there was a statistically significant expansion of the Hadley cell from 1968, which was forced by an increasing surface global warming. There is a strong association between this expansion and the intensification and shift of the subtropical dry zone towards the pole, and these 2 factors potentially explain the trends of droughts in the subtropical regions such as southern Australia, South America and Africa. The observed amount of Hadley expansion is not adequately simulated by the coupled models from the CMIP5, which show only about ¼ of the expansion as determined by the 20CR, and it is only when greenhouse gas forcings are included in simulations, as opposed to simulations that include natural forcings only.

Sources & Further reading

1. Nguyen, H., C. Lucas, A. Evans, B. Timbal and L. Hanson (2015). "Expansion of the Southern Hemisphere Hadley Cell in Response to Greenhouse Gas Forcing." Journal of Climate 28(20): 8067-8077.