Variation of ground level ozone concentrations and total column ozone concentrations over Klang Valley

Abstract

Ozone exists in the upper atmosphere (the stratosphere) and the lower atmosphere (the troposphere). Ozone impacts life on the Earth either positively or negatively depending on where it is in the atmosphere. Ozone in the upper atmosphere absorbs harmful UV rays but ozone is considered as an air pollutant in the lower atmosphere. In this study, variations of ground level ozone (GLO) and total column ozone (TCO) concentrations over Klang Valley, Malaysia in 2013 were determined. The GLO measurement data was acquired from Department of Environment (DOE) Malaysia and is measured using standard method instrument, UV Absorption Ozone Analyzer Model 400A while, TCO measurement using Ozone Monitoring Instrument (OMI) onboard the Aura satellite. The descriptive analysis shows GLO concentrations in all four stations in Klang Valley surpassed the 90 ppb recommended limit suggested in the Malaysia Ambient Air Quality Standard (NMAAQS) (2020). The diurnal variation of GLO exhibited highest maximum GLO concentration is in Shah Alam (141 ppb). Meanwhile, the highest TCO concentration was observed in Petaling Jaya with 286.4 DU. Analysis of TCO time series trend shows the existence of seasonal variation contributed by Northeast Monsoon (NEM) and Southwest Monsoon (SWM) as TCO concentration is the highest during SWM with an average 290 DU and the lowest during NEM with average 230 DU. This is due to environmental conditions such as low precipitation, low relative humidity, high temperature and long sunlight hours during SWM that favour an increase in TCO concentration. In contrast, high precipitation, high relative humidity, low temperature, and short sunlight hours lead to lowest TCO concentration during NEM. GLO trend analysis shows peaks mostly at the end of March to April and October (40 to 50 ppb). This is during transitional monsoon period which also has lower precipitation than other monsoon seasons. Conclusively, both TCO and GLO concentration in Klang Valley influences by monsoon season, where TCO show significant fluctuation between NEM and SWM, while GLO reached higher concentration in transitional monsoon period.