The Use of Vertical Cross Sections in Physics Development for Convection-Allowing Scale NAM Nests

The NCEP NAM suite was upgraded in August of 2014 to include the new Ferrier-Aligo microphysics scheme aimed at providing realistic forecasts of deep convection from the convection-allowing scale 4 km NAM nest. It was through an exhaustive analysis of 3D cloud fields, processes and radar reflectivity that more realistically looking storm structures were realized.

The mesoscale group at EMC now generates vertical cross sections internally on a nearly daily basis of meteorological fields for various locations across CONUS and Alaska in order to monitor performance and to identify possible areas for physics improvement for future model upgrades. The cross sections are designed for monitoring fields considered important to the various NCEP centers such as AWC, SPC and WPC. The vertical cross sections include the more traditional fields such as vertical velocities, temperature, horizontal winds in addition to microphysics cloud species and processes, cloud bases and tops, horizontal visibility, cloud ceiling heights, PBL height as well as TKE.

EMC is now running experimental NAM runs with CONUS nests increased to 3-km resolution as a candidate for the next NAM upgrade in late 2015. Evaluations on almost a daily basis use cross sections to help EMC physics developers better understand the processes and responses associated with physics changes. An example of the parallel 3-km NAM nest capturing moistening of the low-levels better than the operational 4-km NAM nest in a recent winter case over DC will be shown. Examples of additional insights gained from these cross sections will also be shown.