Variations in weekday and weekend surface ozone levels: An analysis of observed and model forecast frends

The performance of the Eta-CMAQ air quality model forecast system for surface level O3 concentrations in the northeast U.S. was examined for the May-September, 2004 period and found to vary between the weekdays and weekends. Model estimates of 1-hr and 8-hr maximum daily ozone concentrations were compared to comparable observations from surface monitoring networks. The forecast system tends to perform better on weekends than weekdays with smaller errors and biases on weekends. Both the observed and model forecast surface O3 levels on weekdays and weekends will be examined to see if the forecast system can capture the observed signals. The influence of cloud cover on the results will be explored to assess if the performance variations are related to the cloud cover fractions. The reasons for these variations will be investigated. When the 2005 ozone forecast data are available, additional analysis will be conducted to determine if similar variations still exist for the 2005 forecast. The weekday and weekend variation pattern over space will also be investigated.

Disclaimer The research presented here was performed under the Memorandum of Understanding between the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Commerce's National Oceanic and Atmospheric Administration (NOAA) and under agreement number DW13921548. Although it has been reviewed by EPA and NOAA and approved for publication, it does not necessarily reflect their policies or views.