As Earth’s climate changes, the weather changes along with it. Recent research suggests that rising temperatures will drive an increase in severe storms, including tropical cyclones, monsoons, and flash floods. These events can be devastating for communities in the region, but tropical weather prediction remains a challenge for scientists. Computer models need to assess a range of physical processes across a wide range of scales in order to simulate wind shifts in the cumulonimbus cloud systems that make up the backbone of tropical weather phenomena. Here Bretherton and Khairoutdinov analyze the processes behind tropical storm formation to better understand how these processes may behave in a warming world.
Tropical cyclones form through a process known as convective self-aggregation, which takes place when the atmosphere develops bifurcated “patches” of air: a motionless dry patch and a moist patch that circulates because of density differences in the air. Moist patches are distinguished by higher rain fall and more high clouds. Past models of cumulonimbus convection systems have simulated convective self-aggregation over large regions and indicate that in uniformly warm ocean atmospheric and oceanic conditions, this process happens spontaneously—and these patches can grow, gain strength, and potentially turn into cyclones. However, this phenomenon also interacts with larger-scale processes, like the interaction between the warm tropics and the cool midlatitudes.
To examine these interactions, the researchers modeled tropical atmospheric changes over a 30-day period. They found that humid, moist patches were boosted by radiative feedback or heat lost through thermal radiation. However, the exchange of heat between the ocean surface and the atmosphere—known as heat flux—actually prevented moist patches from forming. These results indicate that both feedbacks influence the formation of large, slow-forming weather systems, like the Madden-Julian Oscillation.
This new type of model may also be suitable for assessing other tropical weather factors, like the impact of increasing atmospheric carbon dioxide on sea surface temperatures. (Journal of Advances in Modeling Earth Systems (JAMES), doi:10.1002/2015MS000499, 2015)
—Lily Strelich, Freelance Writer
Citation: Strelich, L. (2016), Climate change influences the dynamics behind tropical cyclones, Eos, 97, doi:10.1029/2016EO051301. Published on 27 April 2016.