A database and tool for boundary conditions for regional air quality modeling: description and evaluation

Abstract

Abstract. Transported air pollutants receive increasing attention as regulations tighten and global concentrations increase. The need to represent international transport in regional air quality assessments requires improved representation of boundary concentrations. Currently available observations are too sparse vertically to provide boundary information, particularly for ozone precursors, but global simulations can be used to generate spatially and temporally varying lateral boundary conditions (LBC). This study presents a public database of global simulations designed and evaluated for use as LBC for air quality models (AQMs). The database covers the contiguous United States (CONUS) for the years 2001-2010 and contains hourly varying concentrations of ozone, aerosols, and their precursors. The database is complemented by a tool for configuring the global results as inputs to regional scale models (e.g., Community Multiscale Air Quality or Comprehensive Air quality Model with extensions). This study also presents an example application based on the CONUS domain, which is evaluated against satellite retrieved ozone and carbon monoxide vertical profiles. The results show performance is largely within uncertainty estimates for ozone from the Ozone Monitoring Instrument and carbon monoxide from the Measurements Of Pollution In The Troposphere (MOPITT), but there were some notable biases compared with Tropospheric Emission Spectrometer (TES) ozone. Compared with TES, our ozone predictions are high-biased in the upper troposphere, particularly in the south during January. This publication documents the global simulation database, the tool for conversion to LBC, and the evaluation of concentrations on the boundaries. This documentation is intended to support applications that require representation of long-range transport of air pollutants.

Impacts of Different Characterizations of Large-Scale Background on Simulated Regional-Scale Ozone Over the Continental United States

“…Previous studies deriving regional-scale boundary conditions from global scale models noted the importance of maintaining sufficient 25 vertical resolution in the upper troposphere / lower stratosphere in the regional model (Lin et al, 2009) and properly mapping chemical species between the modeling systems (Henderson et al, 2014). A list of the species mapped between the global models and CMAQ is shown in Table 1 and a depiction of the vertical layers used in the global models and regional CMAQ simulations is provided in Figure 1.…”

Aerosol indirect effect on the grid-scale clouds in the two-way coupled WRF–CMAQ: model description, development, evaluation and regional analysis

“…The chemical boundary conditions (BCs) for the CMAQ model simulation over the CONUS were provided by an annual 2006 GEOS-Chem (Bey et al, 2001) simulation. A detailed description of mapping GEOS-Chem species to CMAQ species for LBCs is presented by Henderson et al (2014).…”

A framework for expanding aqueous chemistry in the Community Multiscale Air Quality (CMAQ) model version 5.1

“…Results are examined after 10 days of spinup from clean default initial conditions. Hourly lateral boundary conditions were taken from a global GEOS-Chem simulation from the same period (Henderson et al, 2014). Gas-phase and aerosol chemistry was simulated with the SAPRC07TIC chemical mechanism Lin et al, 2013) and AERO6i aerosol module, respectively (http://www.airqualitymodeling.org/index.…”