Ground-level ozone (O3) is formed by photochemical reactions between precursors and sunlight, which are controlled by climatic conditions such as relative humidity and temperature. As a result, the purpose of this research was to examine into the influence of relative humidity and temperature in the fluctuation and transformation of O3. The Department of Environment (DoE) contributed hourly monitoring data for O3, relative humidity, and temperature in Shah Alam in 2010, which then was extracted for the nighttime O3 data. Descriptive statistics, box and whisker plots, time series, and diurnal plots were used to examine the observations. Descriptive statistics, box and whisker plots, time series, and diurnal plots were used to examine the observations. During the night, the diurnal plot revealed an inverse link between O3 concentration and relative humidity. During the night, however, temperature is positively associated with O3 concentration. The diurnal trend of O3 concentration revealed that it was greater during the day than at night. As a result of the pollutant deposition process being reduced, decreased air humidity permitted higher ground level ozone concentrations in the atmosphere

• Air pollution,
• secondary air pollutant,
• precursors,
• photochemical reactions,
• temperature,
• Malaysia,

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