Sud, Y. C., D. M. Mocko, and S.-J. Lin, 2006: Performance of two cloud-radiation parameterization schemes in the fvGCM for anomalously wet May and June 2003 over the continental United States and Amazonia. J. Geophys. Res. Atmos., 111(D6), 6201, doi:10.1029/2005JD006246.
An objective assessment of the impact of a new cloud-scheme, called McRAS (together with its radiation modules) on the finite volume GCM was made with a set of ensemble forecasts that invoke performance evaluation over both weather and climate time-scales. The performance of McRAS (and its radiation modules) was compared with that of the NCAR-CCM3 cloud scheme (with its NCAR physics radiation). We specifically chose the boreal summer months of May and June 2003 that were characterized by an anomalously wet eastern half of the continental United States as well as the northern regions of Amazonia. The evaluation employed an ensemble of seventy daily 10-day forecasts covering the 61 days of the study period. Each forecast was started from the analyzed initial state of the atmosphere and spun-up soil-moisture from the first-day forecasts with the model. Monthly statistics of these forecasts with up to 10-day lead-time provided a robust estimate of the behavior of the simulated monthly rainfall anomalies. Patterns of simulated versus observed rainfall, 500-hPa heights, and top-of-the-atmosphere net radiation were recast into regional anomaly correlations. The correlations were compared among the simulations with each of the schemes. The results show that fvGCM with McRAS and its radiation package performed discernibly better than the original fvGCM with CCM3 cloud physics plus its radiation package. The McRAS cloud scheme also showed a reasonable positive response to the observed SST on mean monthly rainfall fields at different time-leads. This analysis represents a method of helpful systematic evaluation prior to selection of new scheme in a global model.
