Monsoons and Their Response to Climate Change in Idealized GCM Experiments

Thursday, 18 December 2014
Anne Laraia and Simona Bordoni, California Institute of Technology, Pasadena, CA, United States
Monsoons are prominent features of the tropical and subtropical atmospheric circulation, affecting 60% of the world’s population (Wang 2006) and sustaining rapidly growing economies. Understanding how monsoons will change with changing climate is of pressing societal importance, and yet remains a challenge: Numerous studies have explored the impact of global warming on monsoons, but many questions remain unanswered.

In this study, we perform experiments with an idealized General Circulation Model (GCM) to investigate the response of an idealized monsoon to climate change. We focus on two idealized continental geometries, an Africa-like continent stretching from pole to pole with a fixed longitudinal width, and an Asia-like continent that spans all longitudes north of 10°N. The climate is varied by perturbing the atmospheric longwave absorber, in analogy to changes in greenhouse gas concentrations. We use the moist static energy, moisture and zonal momentum budgets (e.g., Chou et al. 2001, Bordoni and Schneider 2008) to interpret the simulated changes in monsoon onset, circulation strength and precipitation. Each budget is decomposed into mean, stationary and transient eddy fluxes, to explore the relative role of these circulations in the maintenance of the monsoonal precipitation. We specifically focus on how the distribution, both spatially and temporally, of precipitation changes as the climate is varied in the two different continental configurations.