Performance of the HOMME dynamical core in the aqua-planet configuration of NCAR CAM4: Equatorial waves

For this we compared the results with two other established models in CAM4 framework, which are the finite-volume (FV) and Eulerian spectral (EUL) dynamical cores. Although the gross features seem to be comparable, important differences have been found among the three dynamical cores. The phase speed of Kelvin waves in HOMME is faster and more satisfactory than those in FV and EUL.

The higher phase speed is attributed to an increased large-scale precipitation in the upper troposphere and a more top-heavy heating structure. The variance of the n=1 equatorial Rossby waves is underestimated by all three of them, but comparatively HOMME simulations are more reasonable. For the n=0 eastward inertiogravity waves, the variances are weak and phase speeds are too slow, scaled to shallow equivalent depths.

However, the variance in HOMME is relatively more compared to the two other dynamical cores. The mixed Rossby-gravity waves are feeble in all the three cases. In summary, model simulations using HOMME are reasonably good, with some improvement relative to FV and EUL in capturing some of the important characteristics associated with equatorial waves.