Abstract
High ground-level ozone (GLO) concentrations will adversely affect human health, vegetations as well as the ecosystem. Therefore, continuous monitoring for GLO trends is a good practice to address issues related to air quality based on high concentrations of GLO. The purpose of this study is to introduce stationary and non-stationary model of extreme GLO. The method is applied to 25 selected stations in Peninsular Malaysia. The maximum daily GLO concentration data over 8 hours from year 2000 to 2016 are used. The factors of this distribution are anticipated using maximum likelihood estimation. A comparison between stationary (constant model) and non-stationary (linear and cyclic model) is performed using the likelihood ratio test (LRT). The LRT is based on the larger value of deviance statistics compared to a chi-square distribution providing the significance evidence to non-stationary model either there is linear trend or cyclic trend. The best fit model between selected models is tested by Akaike's Information Criterion. The results show that 25 stations conform to the non-stationary model either linear or cyclic model, with 14 stations showing significant improvement over the linear model in location parameter while 11 stations follow the cyclic model. This study is important to identify the trends of ozone phenomenon for better quality risk management.
Highlights
Extreme ground-level ozone (GLO) in this study refers to the maximum value of GLO concentration in a specific period of time such as yearly, monthly, biweekly or weekly
Continuous monitoring for GLO trends is important to ensure that the level of ozone concentration does not exceed the standard recommendation stated by the National Ambient Air Quality Standard (NAAQS) and Malaysia Ambient Air Quality Standard (MAAQS)
In 25 stations operated by a private firm known as Alam Sekitar Malaysia Sdn Bhd (ASMA) employed by the Department of Environment (DOE) Malaysia, this datum was measured at the monitoring site
Summary
Extreme ground-level ozone (GLO) in this study refers to the maximum value of GLO concentration in a specific period of time such as yearly, monthly, biweekly or weekly. Continuous monitoring for GLO trends is important to ensure that the level of ozone concentration does not exceed the standard recommendation stated by the National Ambient Air Quality Standard (NAAQS) and Malaysia Ambient Air Quality Standard (MAAQS). Most of the studies found that there are seasonal variations in GLO according to locations which are influenced by the interchange of the two monsoons, namely the Northeast Monsoon and the Southeast Monsoon. Most literatures such as in [8]–[11] are focused on the centre of distribution rather than the tail distribution which may contain extreme values. As for non-stationary model, linear and cyclic trends for the location parameter that is dependent on time were considered
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