GF Testing

Hierarchical Testbed Overview

This test was conducted using a hierarchical testbed, consisting of a Single Column Model (SCM) and three-dimensional global model.

SCMs have long been a staple of parameterization evaluation in the research community since they are the simplest way to test a physics suite as an entity. They provide an opportunity to examine complex atmospheric phenomena on a physics suite level while eliminating any bias from a dynamical core. Further, they offer a simple way to pinpoint errors due to a particular parameterization type. SCMs must be initialized and driven with observational or idealized datasets, and for this test the ARM Tropical Warm Pool - International Field Experiment was used. Additional details on the SCM configuration used for this test can be found here.

For the next level of complexity, the test employed the Global Forecast System (GFS), which was configured with lower-than-operational resolution and was run in free-forecast mode (that is, no cycled data assimilation was performed). This simple setup allowed examining the correctness of integration of the experimental parameterization with the dynamic core, and permitted a preliminary evaluation of the forecast skill. Three months of forecasts were conducted as a way to obtain a robust evaluation. Additional details on the global model configuration used for this test can be found here.

Figure 1. Diagram illustrating the testing hierarchy plan to support physics development for NGGPS. LR indicates low resolution, MR medium resolution, and HR high resolution. Color shading indicates where the different groups are anticipated to focus their efforts (red - physics developers, blue - GMTB task within the DTC, and green - EMC). PP stands for physics parameterization.