Using "Heat Tagging" to Understand the Remote Influence of Atmospheric Diabatic Heating through Long-Range Transport

In the circulating atmosphere, diabatic heating influences the potential temperature content of air masses far from where the heating occurs. Budgets that balance local diabatic sources with local heat divergence and storage do not retain information about this remote influence, which requires airmass tracking. In this study, a process-based, passive-tracer diagnostic, called heat tagging, is introduced. Heat tagging locally decomposes the potential temperature into contributions from the distinctive diabatic processes that generate them, wherever they occur. The distribution, variability, and transport of atmospheric heat tags are studied in the relatively simple setting of an idealized aquaplanet model. Heat tags from latent heating are generated in the deep tropics and the midlatitude storm track and then transported throughout the troposphere. By contrast, dry sensible heat tags are enhanced near the surface, and radiative tags are mainly confined to the stratosphere. As a result, local heat transport, variability of potential temperature, and global poleward heat transport are dominated by heat tags related to latent heating, with heat tags from sensible and radiative heating only making contributions in the polar near-surface and the stratosphere, respectively. Heat tagging thus quantifies how water vapor and latent heating link the structural characteristics of the atmosphere and illustrates the importance of the hydrological cycle in poleward energy transport.