The Effects of Weather on Surface Ozone Formation

By M. Pulikesi¹, P. Baskaralingam², D. Elango³, V.N. Rayudu 4, V. Ramamurthi 5 and S. Sivanesan 6
July 2005

Authors Designation
1, 2 = Research Scholar, Department of Chemical Engineering - A.C. College of Technology, Anna University, in Chennai - India
3 = Senior Lecturer, Hindustan College of Engineering
4 = Officer, Tamil Nadu Pollution Control Board
5 = Professor and Head, Department of Chemical Engineering
6 = Assistant Professor, Department of Chemical Engineering

The effects of Meteorological parameters on Tropospheric ozone were studied during October 2004 for the period of one week in the southern part of the Indian peninsula, Chennai. As per the Air quality Index the present surface ozone level was moderate to the public health.

Key words: Surface ozone, Metrological Parameters, High-pressure system

Introduction

Ozone in the troposphere is a pollutant, a constituent of Smog. Much highly energetic reaction produces ozone, ranging from combustion to photochemistry. Weather patterns play a major role in terminating episodes of high ozone concentrations. Meteorological processes directly determine whether ozone precursor´s species are contained locally or transported downwind with the resulting ozone. Wind speed also plays a major role in the formation of ozone. Ozone formation is most conducive during warm, dry, and cloudless days with low wind speeds; these conditions most often occur during high-pressure systems (National academy press, Washington, D.C. 1991).

Objective of this study is to study how weather processes affect tropospheric ozone distribution in Chennai.

Material and Methods

Continuous measurement of Surface ozone is made by UV-absorption based analyzer, at the roof of the Alagappa College of Technology building, Anna University, Chennai.

An analyzer from Environment S.A, (Module O342M) France has been used for the measurement of ozone at this site. This O342M monitor is specially equipped with a software function called "automatic response time" (TR11) which enables filtration of measurements depending on evolution of concentrations. Instrument calibration was performed using an in-built ozone generator. More description of the system used in this includes its calibration, Zero checking, maintenance and other details have been given elsewhere (Naja and Lal, 1996; Naja; 1997, Lal et al 1998, 2000.

The meteorological parameters such as wind direction, Wind speed and Pressure were collected with the help of Indian Meteorological Department, Meenambakam, Chennai.

Results and Discussions

Figure 1 shows the variation of average ozone concentrations with average meteorological parameters in the month of October 2004 for the period of one week in Chennai. An increase in surface ozone concentration during mid morning to early evening (8.00AM-17.00AM) was recorded. This is due to the greatest amount of solar radiation was most direct and air temperatures become quite high. We also found from the graph ozone and Relative humidity was strongly anticorrelated. Newell et al [1996, 1999], and Browell et al [1996] also found similar trend at MOZIAC and PEM data sets. The maximum temperature has 30°C during the monitoring period.

Figure 1 - Variation of surface ozone and meteorological parameter at Chennai

Figure 1

Figure 2 shows that the Ozone concentration increases slightly with increasing wind speed. During the monitoring period the wind direction was mostly NE and N.

Figure 2 - Variation of surface ozone with wind speed at Chennai

Figure 2

Conclusions

The relationship between Surface ozone and various meteorological parameters, like relative humidity, temperature, wind direction and wind speed was examined for Chennai. Following are the conclusions drawn from the present study.

Acknowledgements

We are very grateful to thank the Department of Science and Technology, New Delhi, for financially supporting this research. We also thank Indian Meteorological Department, Meenambakam, Chennai for providing Meteorological data.

References

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