Abstract
The intertropical convergence zone (ITCZ) exports energy and imports
moisture in a way that has been well-understood for decades. By
analyzing a set of uniform, non-rotating aquaplanet simulations we show
that energy export and moisture convergence are general characteristics
of warm humid regions, and not just of the ITCZ. Using an analysis
method based on the column relative humidity, we find that the
absorption of longwave radiation by clouds provides the necessary energy
source to balance the horizontal energy export out of humid regions. The
longwave absorption also induces a thermally direct circulation which
lifts water vapor and leads to low-level moisture convergence into
regions that are already quite humid. This feedback is similar to other
cloud-longwave feedbacks which have been previously studied.