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

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 consider as pollutant gas at the lower atmosphere. It is necessary to monitor both ground level ozone (GLO) and total column ozone (TCO). In this study, variations of ground level ozone (GLO) and total column ozone (TCO) concentrations over Klang Valley, Malaysia 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 concentrations is in Shah Alam (141 ppb). Meanwhile, Shah Alam observed the highest TCO (296 DU) followed by Petaling Jaya (294.20 DU), Klang (293.80 DU) and Nilai (290.50 DU). Analysis of TCO 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 average 290 DU and the lowest during NEM with average 230 DU. This is due to environmental condition such as low precipitation, low relative humidity, high temperature and long sunlight hours during SWM that favour towards 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 in the end of March to April and October (40 to 50 ppb). This is during transitional monsoon period which also have lower precipitation than normal. The correlation between TCO and GLO shows weak positive relation in between 0.03 to 0.30, thus, an increase in GLO concentration not greatly influence the TCO concentration.