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Forecasting Urban Pm10 and Pm2.5 Pollution Episodes In Very Stable Nocturnal Conditions and Complex Terrain Using Wrfechem Co Tracer Model

Abstract

This study presents a system to predict high pollution events that develop in connection with enhanced subsidence due to coastal lows, particularly in winter over Santiago de Chile. An accurate forecast of these episodes is of interest since the local government is entitled by law to take actions in advance to prevent public exposure to PM10 concentrations in excess of 150 mg m3 (24 h running averages). The forecasting system is based on accurately simulating carbon monoxide (CO) as a PM10/PM2.5 surrogate, since during episodes and within the city there is a high correlation (over 0.95) among these pollutants. Thus, by accurately forecasting CO, which behaves closely to a tracer on this scale, a PM estimate can be made without involving aerosol-chemistry modeling. Nevertheless, the very stable nocturnal conditions over steep topography associated with maxima in concentrations are hard to represent in models. Here we propose a forecast system based on the WRFeChem model with optimum settings, determined through extensive testing, that best describe both meteorological and air quality available measurements. Some of the important configurations choices involve the boundary layer (PBL) scheme, model grid resolution (both vertical and horizontal), meteorological initial and boundary conditions and spatial and temporal distribution of the emissions. A forecast for the 2008 winter is performed showing that this forecasting system is able to perform similarly to the authority decision for PM10 and better than persistence when forecasting PM10 and PM2.5 high pollution episodes. Problems regarding false alarm predictions could be related to different uncertainties in the model such as day to day emission variability, inability of the model to completely resolve the complex topography and inaccuracy in meteorological initial and boundary conditions. Finally, according to our simulations, emissions from previous days dominate episode concentrations, which highlights the need for 48 h forecasts that can be achieved by the system presented here. This is in fact the largest advantage of the proposed system.

Article / Publication Data
Active/Online
YES
Volume
45
Available Metadata
Accepted On
February 01, 2011
DOI ↗
Early Online Release
February 06, 2011
Fiscal Year
Peer Reviewed
YES
Publication Name
Atmospheric Environment
Published On
May 01, 2011
Publisher Name
Science Direct
Print Volume
45
Print Number
16
Page Range
2769-2780
Issue
16
Submitted On
October 10, 2010
URL ↗

Institutions

Not available

Author

Authors who have authored or contributed to this publication.

  • Mariusz Pagowski - seventh Gsl
    Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder
    NOAA/Global Systems Laboratory