Error and energy budget analysis of a non-hydrostatic stretched-grid global atmospheric model

Abstract:

A non-hydrostatic stretched-grid (SG) model is used to analyze the large-scale errors generated by the stretching of horizontal grids and their influences to the region of interest. Simulations by a fully compressible non-hydrostatic global atmospheric model, NICAM, and its SG regional model, a Stretched-NICAM, were performed for March-April-May 2011 with various resolutions and global stretching factors. The comparison of weeklong accumulative precipitation amounts between the Tropical Rainfall Measuring Mission (TRMM) satellite data, the quasi-uniform and SG simulations have shown that a stretched run leads to better representation of storms and associated precipitation, since the errors generated in the outer regions with a coarser grid spacing do not seriously affect the inner domain centered at the focal point. For season-long simulations, in one particular set of stretched runs with the focal point located in the eastern U.S., a larger grid spacing causes the artificial suppression of baroclinic development of mid-latitude eddies in the Southern Hemisphere, weakens the eddy-driven polar-front jet (PFJ), and resulting in a cold bias at mid- to high-latitudes. However, in the Northern Hemisphere, by contrast, the aforementioned changes are less apparent, such that each hemisphere acting nearly independent of the other. Therefore, for the SG runs, the mean temperature was maintained at the region of interest and the increased number of moderate to heavy precipitations, which are also frequent in TRMM, were observed, thus the benefits of increased resolution are realized.