Numerical Exploration of the Stable Atmospheric Boundary-Layer

Simulating the stable atmospheric boundary-layer (SABL) presents a significant challenge to numerical models due to the interactions of several processes with widely varying scales. The goal of this Challenge Project is to more clearly define the role of gravity waveturbulence interactions as a mechanism for localized destabilization in the SABL. The numerical scheme employed is a fully prognostic second-order closure (SOC) scheme implemented in the National Taiwan University/Purdue University Nonhydrostatic model (NTU/P). Use of second-order closure is more complex and resource intensive than eddy-viscosity (EV) schemes; however, we find the SOC scheme adds significant detail. Growth rates for the primary and secondary instabilities were greater, even when compared to EV model runs with doubled resolution. The enhanced detail includes the excitation of gravity waves via non-linear interaction between Kelvin-Helmholtz modes, which is much more evident when the SOC scheme is used. As part of the verification efforts, just now commencing, we are employing observational data from the Meteor Crater Experiment in 2006 to study boundary layer evolution as well as transient features generated by wind flow over the crater.