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Simulation of Particulate Matter Distribution over Iowa

Abstract

This paper discusses a Weather Research and Forecast Model with chemical processes (WRF-CHEM) that was used to simulate the transport of particulate matter with diameter less than 2.5 micrometers (PM 2.5) over Iowa. These forecasts were compared to surface monitor measurements of PM 2.5 concentration and measurements of aerosol optical depth from the MODIS (Moderate Resolution Imaging Spectradiometer) sensor. Several episodes of high PM 2.5 concentrations during the years 2000 – 2003 were examined. A Box Model was used to estimate the relative size of transport processes to emissions and particulate mass tendency.

Simulations of atmospheric conditions demonstrated overall satisfactory agreement with observed data, suggesting that WRF-CHEM could be used to simulate pollution movement and mixing. The average linear correlation coefficients between simulated and measured PM 2.5 concentrations for three cases examined more closely were found to be greater than those reported in the literature. Satellite and surface observations appeared to be in reasonable agreement with model predictions. Nevertheless, various uncertainties in PM simulation have been identified. Substantial underforecasting of surface PM 2.5 concentration was found. The Box Model budgets for particulate matter revealed relatively large residual components. Results of the present research may serve as a basis for further work with WRF- CHEM on the dispersion of other pollutants (e.g., nitrogen compounds) and the contribution from adjacent states in the environmental engineering.

1. Introduction

Numerous air pollution episodes are characterized by particulate matter (PM) suspended in the troposphere. Though human activities have emitted particles into the atmosphere since pre-industrial times, emissions have increased notably since the 1950s1). The increased aerosol concentration not only changes the environment (for example, alters visibility), but also influences the earth-atmosphere energy budget. Aerosols directly absorb and backscatter incoming solar radiation and, by serving as cloud condensation nuclei, indirectly modify the optical properties and lifetimes of clouds. This has an impact on global and regional climate. Moreover, fine particulate matter can lead to adverse health effects. For these reasons, aerosol studies are highly important2, 3.

The goal of this study is to evaluate a budget for fine particulate matter with diameter less than 2.5 micrometer (hereafter, PM 2.5) over Iowa. A Box Model is used to examine the relative size of transport processes to emissions and particulate mass tendency. The study of particulate matter dispersion is a complicated problem, involving both meteorological factors (such as wind speed and direction, turbulence, radiation, clouds, and precipitation) and chemical processes (such as deposition and transformation). Correspondingly, the physical consistency of numerical simulations can be the most appropriate way to examine the complex interactions of the meteorology and chemistry involved in air quality issues. The source of data for this study is the Weather Research and Forecast Model with Chemical processes (WRF-CHEM Model). The paper examines aerosol episodes (instances when concentrations of PM 2.5 are close to or higher than the National Ambient Air Quality Standards) during the years 2000 – 2003, and compares the WRF-CHEM simulations to satellite and surface data. Results

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Korotkova, S., & Czarnetzki, A., & McCready, K. (2006, June), Simulation Of Particulate Matter Distribution Over Iowa Paper presented at 2006 Annual Conference & Exposition, Chicago, Illinois. 10.18260/1-2--1426