Characterizing the North American monsoon in the Community Atmosphere Model: Sensitivity to resolution and topography

Observations are used to evaluate the fidelity of the representation of the monsoon in simulations from the Community Atmosphere Model version 5 (CAM5) with a standard 1.0 degrees grid spacing and a high-resolution 0.25 degrees grid spacing. The simulated monsoon has some realistic features, but both configurations also show precipitation biases.

The default 1.0 degrees grid spacing configuration simulates a monsoon with an annual cycle and intensity of precipitation within the observational range, but the monsoon begins and ends too gradually and does not reach far enough north. This study shows that the improved representation of topography in the high-resolution (0.25 degrees grid spacing) configuration improves the regional circulation and therefore some aspects of the simulated monsoon compared to the 1.0 degrees counterpart.