08 December 2017

Understanding the Sensitivity of the Mean State of the Community Atmosphere Model (CAM) to Horizontal Resolution


An explanation for the sensitivity of the large-scale circulation to resolution was developed from an analysis of aqua-planet simulations, arguing that dynamical core response to the physical parameterizations is inversely proportional to the truncation scale.


Our study focused on understanding the resolution sensitivity observed in CAM, in an effort to develop and make use of variable resolution capabilities in CAM for climate simulations that explore extreme weather impacts.


The authors analyzed regional energy and moisture budget components, and their change with increasing resolution, on a common grid. Large reductions in moisture and cloud cover with resolution were found to balance an increase in Hadley Cell overturning. Resolved vertical motion in the ascending branch of the Hadley Cell increase with resolution, and shown no indication of convergence. The authors formulated an explanation for the increase in resolved vertical motion through interpreting the hydrostatic vertical velocity scale as inversely proportional to the horizontal scale of the buoyancy forcing from the physical parameterizations. In the ascending branch of the Hadley Cell, the forcing scale is observed to reflect the truncation scale of the model, providing an explanation for the increase in vertical velocity scale with resolution.

Kevin A. Reed
Stony Brook University