Estimation of Ozone Trend in Central Greece, Based on Meteorologically Adjusted Time Series

Abstract

Data referring to an approximately 8-year period (1999-2007) are analyzed in order to estimate the trend of the daily maximum hourly value of ozone concentration at the east coast of central Greece, where the summer background ozone concentration is high. A Kolmogorov-Zurbenko filter is applied to remove the short-term component from the raw time series of ozone and meteorological variables. Regression models are developed in order to produce meteorologically adjusted ozone time series, involving the noise-free temperature, relative humidity, and wind speed as independent variables. The analysis verifies that the meteorological adjustment provides better results on estimating ozone's trend, which is found to be increasing (alpha = 0.001) with an annual rate of 1.34 +/- 0.07 mu g/m(3). This trend could mainly be attributed to policy and changes in the emissions of ozone's precursors. Additionally, the short-term component of ozone concentration is also meteorologically adjusted and its impact on the trend is examined. The analysis shows that its contribution is of minor importance when the ozone trend is adjusted by temperature, relative humidity, and wind speed. Moreover, the sea breeze circulation system that is frequently developed in the area influences the short-term and seasonal ozone variation, and therefore, it should be taken into account when producing meteorologically adjusted time series. The study's conclusions could be exploited by environmental and agricultural authorities in order to develop their long-term strategies towards the air quality management.