Extreme value theory; Gumbel distribution; Time series; Statistical modelling; Air quality standards
Extreme value theory (EVT) has been used for making predictions of the expected number of violations of the National Ambient Air Quality Standards (NAAQS) as prescribed by the Central Pollution Control
Board (CPCB), India, for hourly- and eight-hourly average carbon monoxide(CO) concentration for an Air Quality Control Region (AQCR) comprising of an urban road intersection. Almost 100% contribution to
the CO pollution in the region is due to vehicular traffic. The parameters of the extreme value distribution (EVD) have been estimated by four methods viz. method of moments, maximum likelihood, least square fit and Gumbel's fitting method. Least square fit and Gumbel's method gave the best fit and predictions. A comparison of the predicted violations of NAAQS and the exceedence of the maximum pollution concentration with that of the observed data suggests that the theory performs satisfactorily for the extreme air pollution events.