Environmental Engineering Reference
In-Depth Information
4. Summary
Wavelet analysis provides frequency specific information about observations and
model outputs that can be useful in model evaluation. Differences in the strength
(amplitude) between observations and model were illustrated for low-frequency
(trend) and intra-day variation, while differences in both strength and timing
(phase) were illustrated for seasonal, weekly and diurnal processes. Modulation of
seasonal and diurnal ozone occurs at low frequencies (3-5 years for seasonal and
1 year for diurnal processes) and can be tied to low frequency variation in
meteorological variables. Wavelet analysis of weekly variation can be used to
identify spatial/temporal variation in weekday/weekend ozone air quality.
Acknowledgments and Disclaimer
Christian Hogrefe gratefully acknowledges partial support
for this work through a research fellowship from the Oak Ridge Institute for Science and
Education (ORISE). The model simulations in this paper were supported by National Oceanic
and Atmospheric Administration award NAO40AR4310185185, but the paper has not been
subjected to its required peer and policy review. Therefore, the statements, findings, conclusions,
and recommendations are those of the authors and do not necessarily reflect the views of the
sponsoring agency and no official endorsement should be inferred. This work constitutes a
contribution to EPA's Air Quality Program. Although it has been reviewed by EPA and
approved for publication, it does not necessarily reflect their policies or views.
References
Bloomfield, P. 2000. Fourier Analysis of Time Series: An Introduction. Wiley-Interscience; 2nd ed.
CASTNET. 2006. Annual Report. prepared by MACTEC Engineering and Consulting, Inc. for
the USEPA Clean Air Markets Division, Washington, D.C.
Hogrefe, C., Lynn, B., Goldberg, R., Rosenzweig, C., Zalewsky, E., Hao, W., Doraiswamy, P.,
Civerolo K., Ku, J., Sistla, G., and P.L. Kinney. 2009. A combined model-observation
approach to estimate historic gridded fields of PM2.5 mass and species concentrations.
Atmospheric Environment 43: 2561-2570
