Uniformly rotating global radiative‐convective equilibrium in the Community Atmosphere Model, version 5. (7th December 2015)

• Record Type: Journal Article
• Authors: Reed, Kevin A.; Chavas, Daniel R.
• Is Part Of: Journal of advances in modeling earth systems. Volume 7:Number 4(2015:Dec.)
• Page Start: 1938
• Page End: 1955
• Publication Date: 2015-12-07
• Subjects: radiative‐convective equilibrium -- tropical cyclones -- idealized model -- atmospheric general circulation model; Geological modeling -- Periodicals; Climatology -- Periodicals; Geochemical modeling -- Periodicals; 551.5011
• DOI: 10.1002/2015MS000519
• Languages: English
• ISSNs: 1942-2466

Abstract

Abstract: A standard atmospheric general circulation model is run in a uniformly rotating global radiative‐convective equilibrium configuration to explore the equilibrium state, including the statistics of its constituent tropical cyclones, and its sensitivity to horizontal resolution. The Community Atmosphere Model 5 (CAM5) is run at the conventional resolution of approximately 100 km grid spacing and a high resolution of 25 km grid spacing globally. The setup uses an aqua‐planet configuration with spatially uniform, diurnally varying insolation, uniform fixed sea surface temperatures, and a uniform rotation rate equal to that at 10°N. The resulting state is one in which tropical cyclones fill the global domain, such that storm count and outer storm size covary strongly. At higher resolution, the storm inner core is more intense and compact but the size of the outer circulation decreases only marginally, and storm count increases in a manner consistent with this decrease in size. Furthermore, the size of the wind field and precipitation fields are highly correlated. A simple analytical model is found to robustly reproduce the radial structure of the broad outer storm circulation. Finally, the minimum central pressure is demonstrated to be an exclusive function of peak azimuthal‐mean wind speed and outer storm size. Despite significant changes in the statistics of storm count, intensity, and structure, the mean environment, including the potential intensity, is nearly identical for both simulations. Results are compared with the nonrotating case from a prior study, and a generalized conceptual framework for the interpretation of aggregation with or without rotation is proposed. Key Points: A uniformly rotating RCE CAM5 framework offers insight into the physics of tropical cyclones The mean state is shown to be rather insensitive to horizontal resolution Fundamental role of rotation in aggregation is discussed