MUSICA - Modeling for Chemistry, Weather and Climate

Current chemical transport models inadequately account for the two-way coupling of atmospheric chemistry with other Earth System components over the range of urban/local to regional to global scales and from the surface up to the top of the atmosphere.  To meet future challenges, future modeling systems need to have the ability to (1) change spatial scales in a consistent manner, (2) resolve multiple spatial scales in a single simulation, (3) couple model components which represent different Earth system processes, and (4) easily mix-and-match model components. This is the motivation behind MUSICA - the Multi-Scale Infrastructure for Chemistry and Aerosols, which we develop together with the atmospheric chemistry community. MUSICA will allow simulation of large-scale atmospheric phenomena while still resolving chemistry at scales relevant for representing societal and scientific critical phenomena (e.g. urban air quality, or convection in monsoon regions) and also enable connections to other components of the earth system by fully coupling to land and ocean models. MUSICA objectives will be achieved through development of a global modeling system capable of regional refinement and the new Model Independent Chemistry Module (MICM). We will discuss the infrastructure and show preliminary results of atmospheric chemistry simulations being conducted in a global model with regional refinement: the Community Atmosphere Model with chemistry using spectral element grids that refine from one-degree resolution to ~14 km resolution over the conterminous United States. These early results confirm that model resolution does matter for representing regional air quality and that the two-way feedback between the local and global scale can play an important role.