INFLUX: Comparisons of modeled and observed surface energy dynamics over varying urban landscapes in Indianapolis, IN

The goal of the Indianapolis Flux Project (INFLUX) is to quantify greenhouse gas (GHG) emissions from Indianapolis using atmospheric inversions at high resolution. The mesoscale model WRF is being used to simulate the atmospheric concentrations over the area. In order to better simulate the local dynamics, four eddy-flux towers are to be deployed to optimize model parameters in the land surface and the Planetary Boundary Layer (PBL) schemes. The sites were chosen based on the land surface type located around the site, including one rural site, one dense urban site, and two light/moderate urban sites, which is the dominant land surface landscape in Indianapolis.

Preliminary results using aircraft temperature data (MADIS) suggest that the PBL depth over the city is similar to the PBL depth in the surrounding areas outside of the city, which is counterintuitive from what several urban heat island studies have found in other urban areas. This initial investigation prompted a more thorough and extended investigation into the differences between the varying land surfaces in Indianapolis, IN and what the differences in the surface energy dynamics might be between these different landscapes. We have run several WRF simulations to compare the surface energy components to observations. We investigated the differences between the modeled and observed sensible heat flux, latent heat flux, air temperature, and wind speed. Discrepancies in the timing of the transition from a stable nocturnal layer to a convective boundary layer were also investigated in this study. Finally, we present our strategy to improve both the PBL and the land surface schemes by performing data assimilation of surface and atmospheric observations over urban and vegetated areas. The optimized parameters will be evaluated in our fully coupled modeling system to assess their impact on the atmospheric dynamics.