A new dynamically adaptive mesoscale atmospheric model

The accurate simulation and prediction of gravity waves and their breakdown into turbulent eddies depends to a large extent on the ability to resolve these waves and their orographic and other origins. After breakdown, two important turbulent scales are those affecting optical frequency transmission (“optical turbulence”) and those that affect aircraft operations (“clear air turbulence”). Neither of these turbulence scales are resolved adequately by the inner nests in standard mesoscale models with typical nest numbers and grid refinement ratios. Furthermore, standard nesting techniques are limited by the need to allow extra domain extent in each nest so that the poorly resolved nest boundary values can adjust to the finer mesh spacing.

A new dynamically adaptive model has been developed, based on the well known MM5, to address these and other resolution issues in atmospheric modeling. The non- hydrostatic equations are transformed to a general moving coordinate system. The NCSU dynamic solution adaptive grid algorithm DSAGA is installed to selectively resolve chosen properties or features of the atmosphere or topography.

The paper will include examples in 2-D an 3-D, including video animations, of the use of this technique to model gravity waves and their breakdown. As an example, the figure below depicts potential temperature contours after breakdown of gravity waves in the generic 1972 Colorado windstorm case.