GATOR-GCMM: A global- through urban-scale air pollution and weather forecast model 1. Model design and treatment of subgrid soil, vegetation, roads, rooftops, water, sea ice, and snow

A model that treats nesting of gas, size- and composition-resolved aerosol, radiative, and meteorological parameters from the global through urban sca les (<5-km grid spacing) was developed. The model treats multiple one-way-n ested layers and multiple air quality and meteorological domains in each la yer between the global and the urban scales. This latter feature allows for ecast of air pollution and weather at several urban or regional sites durin g the same simulation. Regardless of the number of domains used during a si ngle continuous simulation, the central memory required never exceeds 1.5 t imes and 2.1 times that of the largest domain for gas and gas/aerosol simul ations, respectively. A submodule was developed for all domains to treat gr ound temperatures, latent heat fluxes, and sensible heat fluxes over subgri d soil types (with and without vegetation), water, sea ice, and urban areas . Urban areas are divided into road surfaces, rooftops, vegetation, and bar e soil. Snow is treated over all surface types. The global-through-urban mo del is applied in a companion paper to study elevated ozone, ozone in natio nal parks, and weather during a field campaign in northern and central Cali fornia.