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Trend Analyses
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Table of Contents
Objectives and Trend Analysis
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One of the PAMS objectives is to provide data to assess trends in ozone and ozone precursor concentrations over time and reconcile these data with trends in precursor emissions.
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Examples for annual summary statistics include the following: Ozone
Hydrocarbons
Useful Initial Information
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METEOROLOGICAL VARIABLES POTENTIALLY ASSOCIATED WITH OZONE FORMATION Insolation Sky cover, integrated clear or cloudy sky photolysis rate, ceiling height, number of daylight hours Ventilation Vector and scalar average wind speeds, wind fluctuation ratio (ratio of scalar to vector average wind speed), mixing height, ventilation coefficient (mixing height times wind speed) Transport Wind direction, recirculation index Indirect Measures Previous day's daily maximum ozone concentration, temperature (daily maximum, range), humidity indicators, surface pressure and range, precipitation, temperature at 500 and 850 mb, synoptic weather pattern type [Workbook Table of Contents] [Top of Trend Analyses] [Previous Section] [Next Section]
High ozone is likely to occur with wind patterns that bring, keep, or return high background concentrations to the region; elevated temperature; intense solar radiation (i.e., no cloud cover); and shallow mixing depth. VOC concentrations are most affected by wind speed, wind direction when there is inhomogeneity in the spatial distribution of sources, and temperature (e.g., for isoprene). Examples
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EPA
METEOROLOGICAL TREND ADJUSTMENT METHOD The Cox and Chu Method is a regression model that can be used to predict the probability distribution of daily maximum ozone concentrations in a metropolitan area given the values of several meteorological parameters including: Surface temperature
The model includes a term to account for the long-term trends in ozone air quality.
Plot of the actual and Cox and Chu model-predicted 95th percentile of
the ozone daily maximum
Figure 12
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SUNYA
TREND ANALYSIS METHOD The Rao and Zurbenko method is a statistical method of moderating the influence of meteorology on surface ozone concentrations. Surface temperature is used as a surrogate for all meteorological parameters assumed to affect ozone. Time series of the log of the daily maximum ozone (O) and daily maximum temperature (T) are represented by X(t) = e(t) + S(t) + W(t) = Baseline(t) + W(t) e(t) = Long-term trend component S(t) = Seasonal variation W(t) = Short-term variation (white noise) The baseline is separated from the short-term variation using the Kolmogorov-Zurbenko (KZm,p) filter. Filtered Ozone-Temperature Correlation Om,p(t) = aTm,p(t+lag) +b + e (t) e (t) reveal changes in ozone concentrations which cannot be attributed to temperature fluctuation. e (t) = e m,p(t) + d (t) e m,p(t) = Long-term emission effects unexplained by temperature d (t) = Ozone seasonal variation induced by meteorological variables other than temperature
Geographical map depicting trends, significant at the 95% confidence
level, in the temperature-independent
Linear Model Use simple linear regression on annual summary statistics or to logged statistics (if lognormal); perform analysis of variance. Nonparametric Methods To test for and estimate a trend without making distributional assumptions (e.g., Spearman's rho test of trend, Kendall's tau test of trend). Time Series Models Statistical modeling of ozone concentrations taking into account their serial dependence (e.g., auto-regressive integrated moving average - ARIMA). Extreme Value Theory To estimate distributions of annual maximum hourly concentrations, estimate distributions of the number of days exceeding the standard (e.g., Chi-square test, Poisson process approximation).
Summary of average expected changes in emissions of several hydrocarbons and ambient data values using species weight fractions at Los Angeles North Main (0600-0900 PDT, summer 1992 and 1993, screened data). Indicator usefulness is expressed as Yes, No, or Possible. A "Possible" indicates the estimated emission change is equal to about one standard deviation or at the edge of the interquartile range. (Stoeckenius et al., 1995)
a Standard deviation
of the daily mean values in the 1992 and 1993 CARB 3-hr hydrocarbon data.
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Bloomfield P., Royle J.A., Steinberg L.J., and Yang Q. (1996) Accounting for meteorological effects in measuring urban ozone levels and trends. Atmos. Environ. 30, 3067-3077. Chinkin L.R., Reiss R., Eisinger D.S., Dye T.S., Jones C.M. (1996a) Ozone exceedance data analysis: representativeness of 1995, Phase I. Final report prepared for the American Petroleum Institute by Sonoma Technology, Inc., Santa Rosa, CA. STI-996031-1574-FR, August. Chinkin L.R., Reiss R., and Eisinger D.S. (1996b) Ozone exceedance data analysis: representativeness of 1995, Phase II. Final report prepared for the American Petroleum Institute by Sonoma Technology, Inc., Santa Rosa, CA. STI-996032-1586-FR, October. Cox W.M. and Chu S.H. (1992) Meteorologically adjusted ozone trends in urban areas: a probability approach. In Transactions of the Tropospheric Ozone and the Environment II International Specialty Conference, Air & Waste Management Association, Pittsburgh, PA, pp. 342-353. Cox W.M. and Chu S.H. (1993) Meteorological adjusted ozone trends in urban areas: a probabilistic approach. Atmos. Environ., 27B, 425-434. Cox W.M. and Chu S.H. (1996) Assessment of interannual ozone variations in urban areas from a climatological perspective, submitted to Atmos. Environ. Fairley D. and Blanchard C.L. (1991) Rethinking the ozone standard. J. Air & Waste Manag. Assoc. 41, 928-936. Flaum J.B., Rao S.T., and Zurbenko I.G. (1996) Moderating the influence of meteorological conditions on ambient ozone concentrations. J. Air & Waste Manage. Assoc., 46, 35-46. Hammond D. (1996) Ambient trends of benzene in California from 1990 through 1995. Paper presented at the U.S. Environmental Protection Agency and Air & Waste Management Association International Symposium on Measurement of Toxic and Related Air Pollutants, Research Triangle Park, NC, May 7-9. Kolaz D.J. and Swinford R.L. (1990) How to remove the influence of meteorology from the Chicago area ozone trend. Presented at the Air & Waste Management Association 83rd Annual Meeting, Pittsburgh, PA, June 24-29. LADCO (1995) Lake Michigan Ozone Study. 1994 data analysis report, version 1.1. Report prepared by Lake Michigan Air Directors Consortium, Des Plaines, IL, May. LADCO (1996) Lake Michigan Ozone Study: 1995 data analysis report, version 1.1. Report prepared by Lake Michigan Air Directors Consortium, Des Plaines, MI, April. Porter P.S., Rao S.T., Zurbenko I., Zalewsky E., Henry R.F., and Ku J.Y. (1996) Statistical characteristics of spectrally-decomposed ambient ozone time series data. Final report prepared for the Ozone Transport Assessment Group by the University of Idaho, the State University of New York at Albany and the New York Department of Environmental Conservation, August. Rao S.T. and Zurbenko I.G. (1994) Detecting and tracking changes in ozone air quality. J. Air & Waste Manage. Assoc., 44, 1089-1092. Rao, S.T., Zalewsky E., and Zurbenko I.G. (1995) Determining spatial and temporal variations in ozone air quality, J. Air & Waste Manage. Assoc., 45, 57-61. Roberts P.T., Main H.H., and Yocke M.A. (1996) Operating plan for ozone modeling data collection in El Paso-Ciudad Juarez-Sunland Park. Draft final report prepared for U.S. Environmental Protection Agency, Research Triangle Park, NC under subcontract to SAIC, McLean, VA by Sonoma Technology, Inc., Santa Rosa, CA, STI-95370-1573-DFR, EPA Contract No. 68-D3-0030, Option Year II, Work Assignment No. 11-77, SAIC Project No. 01-1030-07-3823-xxx, March. Sabo E.J. and Hawes J.T. (1990) User's guide and program documentation for the transported ozone design value model. Report prepared for U.S. Environmental Protection Agency, Research Triangle Park, NC, EPA Contract No. 68-02-4393. Schmidt, M. (1997) Personal communication. Smith B.E. and Adamski W.J. (1996) Long term ozone trends in the Lake Michigan airshed. Paper No. 97-A112 presented at the Air & Waste Management Association 90th Annual Meeting & Exhibition, Toronto, Ontario, Canada, June 8-13. Stoeckenius T.E., Ligocki M.P., Cohen B.L., Rosenbaum A.S., and Douglas S.G. (1994b) Recommendations for analysis of PAMS data. Final report prepared by Systems Applications International, San Rafael, CA, SYSAPP94-94/011r1, February. Stoeckenius T.E., Yarwood G., Ligocki M.P., Cohen J.P., Shepard S.B., Looker R.E.,Fujita E.M., Main H.H., and Roberts P.T. (1995) Feasibility study for a 1995-1996 Southern California air quality monitoring program. Final report prepared for Coordinating Research Council, Atlanta, GA by Systems Applications International, San Rafael, CA, Desert Research Institute, Reno, NV, and Sonoma Technology, Inc., Santa Rosa, CA, SYSAPP94-94/065, January. U.S. Environmental Protection Agency (1994a) Clean air act ozone design value study: a report to Congress. Final report prepared by OAQPS, U.S. Environmental Protection Agency, Research Triangle Park, NC, EPA-454/R-94-035, December. U.S. Environmental Protection Agency (1994b) Air pollutant emission trends: 1900-1994. Prepared by the Office of Air and Radiation , U.S. Environmental Protection Agency, Research Triangle Park, NC. Zurbenko I.G., Rao S.T., and Henry R.F. (1995) Mapping ozone in the eastern United States, Environmental Manager, 1, 24-30. [Workbook Table of Contents] [Top of Trend Analyses] [Previous Section] [Next Section] |
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