Tower-based greenhouse gas measurements and flux estimates in an urban environment

Independent verification of anthropogenic greenhouse gas emissions is an emerging need as legislation to regulate greenhouse gas emissions becomes increasingly likely. However, relatively few atmospheric measurements using towers above the surface layer have been attempted in urban environments. As part of the INFLUX project phase 1, CO ₂, CH ₄ and CO mixing ratios are measured using wavelength-scanned cavity ringdown spectroscopy (Picarro, Inc.) at two towers surrounding Indianapolis, IN. We will quantify spatial patterns in atmospheric mixing ratios of these gases within and around the large urban center at high temporal resolution for several months. We will describe the observed temporal and spatial gradients in CO ₂, CO and CH ₄. We will also describe regional modeling of GHG mixing ratios using emissions inventories and a mesoscale atmospheric transport model, and comparison of the modeled and observed mixing ratios to infer regional fluxes using atmospheric inversion methods. We will also present plans and progress to date for INFLUX phase 2, and expansion of the sampling network to 12 sensors, including ¹⁴CO ₂ measured via flasks.