Abstract
In the companion paper (Lee et al., 2012), it was showed that CMAQ simulation using a lateral boundary conditions (LBCs) derived from RAQMS-CMAQ linkage, compared to the CMAQ results with the default CMAQ LBCs, improved ozone simulations in the conterminous US domain. In the present paper, the study is extended to investigate the influence of LBCs on PM2.5 simulation. MM5-SMOKE-CMAQ modeling system was used for meteorological field generation, emissions preparation and air quality simulations, respectively. Realtime Air Quality Modeling System (RAQMS) model assimilated with satellite observations were used to generate the CMAQ-ready LBCs. CMAQ PM2.5 simulations with RAQMS LBCs and predefined LBCs were compared with U.S. EPA Air Quality System (AQS) measurements. Mean PM2.5 lateral boundary conditions taken from RAQMS outputs showed strong variations both in the horizontal grid and vertical layers in the northern and western boundaries and affected the results of CMAQ PM2.5 predictions. CMAQ with RAQMS LBCs could improve CMAQ PM2.5 predictions resulting in the improvement of index of agreement from 0.38 to 0.63.
Highlights
In order to understand the complex physical and chemical processes in the atmosphere, a number of urban and regional scale air quality models have been developed and applied to address various air quality issues related to aerosols, regional haze, ozone and so on (Russell and Dennis, 2000; Seigneur et al, 1999)
Community Multiscale Air Quality (CMAQ) was run for this period with two different lateral boundary conditions: (1) Predefined constant LBCs, and (2) LBCs from Realtime Air Quality Modeling System (RAQMS) outputs
CMAQ PM2.5 predictions with RAQMS LBCs were compared to CMAQ results with predefined LBCs for the three regions
Summary
Predicting aerosol concentration is more difficult than predicting trace gas (for example, ozone) concentrations (Smyth et al, 2006). This is partially due to the complexity and the limited knowledge on aerosol compositions, structure, phases, and formation mechanisms in the atmosphere. Since the current CMAQ model utilizes fixed lateral boundary condition profiles of the pollutant species, they could not consider spatial and temporal changes at the boundaries. It is, essential to create and provide appropriate boundary conditions data for CMAQ simulations
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