How tropical humidity self-organizes into moist and dry regions



Numerical simulations have shown that the moisture in the tropical troposphere has a tendency to spontaneously aggregate, forming separate wet and dry regions. To learn more about how this self-organization occurs, Craig and Mack introduced a simple equation for the tropical troposphere moisture budget and conducted numerical simulations that included convective moistening and horizontal mixing. Based on their simulations, the authors propose that a feedback process in the troposphere causes moisture to aggregate, beginning on small scales and then coarsening to larger scales. Wet regions become wetter and dry regions become drier as the self-organization continues.