Urban and land surface effects on the 30 July 2003 mesoscale convective system event observed in the southern Great Plains

The urban canopy of excess heat, water vapor, and roughness can affect the evolution of weather systems, as can land vegetative processes. High-resolution simulations were conducted using the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS(R)) to investigate the impact of urban and land vegetation processes on the prediction of the mesoscale convective system (MCS) observed on 30 July 2003 in the vicinity of Oklahoma City (OKC), Oklahoma. The control COAMPS model (hereinafter CONTROL) used the Noah land surface model (LSM) initialized with the Eta Data Assimilation System and incorporates an urban canopy parameterization (UCP). Experiments assessed the impact of land vegetative processes by (1) adding a canopy resistance scheme including photosynthesis (GEM) to the Noah LSM and (2) replacing the UCP with a simpler urban surface characterization of roughness, albedo, and moisture availability (NOUCP). The three sets of simulations showed different behaviors for the storm event. The CONTROL simulation propagated two storm cells through the OKC urban region. The NOUCP also resulted in two cells, although the convective intensity was weaker. The GEM simulation produced one storm cell west of the downtown region, whose intensity and timing were closer to the observed. To understand the relative roles of the urban and vegetation interaction processes, a factor separation experiment was performed. The urban model improved the ability to represent the MCS, and the enhanced representation of vegetation further improved the model performance. The enhanced performance may be attributed to better representation of the urban-rural heterogeneities and improved simulation of the moisture fluxes and upstream inflow boundaries.