|Title||Robustness and sensitivities of central US summer convection in the super-parameterized CAM: Multi-model intercomparison with a new regional EOF index|
|Publication Type||Journal Article|
|Year of Publication||2013|
|Authors||Kooperman G.J, Pritchard M.S, Somerville R.CJ|
|Journal||Geophysical Research Letters|
|Type of Article||Article|
|Keywords||atmosphere; Central; community atmosphere model; diurnal cycle; empirical orthogonal function; episodes; mesoscale convective system; model; multiscale modeling framework; precipitation; super-parameterization; surface; systems; United States; united-states; warm-season|
Mesoscale convective systems (MCSs) can bring up to 60% of summer rainfall to the central United States but are not simulated by most global climate models. In this study, a new empirical orthogonal function based index is developed to isolate the MCS activity, similar to that developed by Wheeler and Hendon (2004) for the Madden-Julian Oscillation. The index is applied to compactly compare three conventional- and super-parameterized (SP) versions (3.0, 3.5, and 5.0) of the National Center for Atmospheric Research Community Atmosphere Model (CAM). Results show that nocturnal, eastward propagating convection is a robust effect of super-parameterization but is sensitive to its specific implementation. MCS composites based on the index show that in SP-CAM3.5, convective MCS anomalies are unrealistically large scale and concentrated, while surface precipitation is too weak. These aspects of the MCS signal are improved in the latest version (SP-CAM5.0), which uses high-order microphysics.