An investigation of the effects of meteorology on air pollution in Makkah

Abstract EN

Air pollutant concentrations are not only affected by emission sources but also by meteorological variables.

Meteorological variables play an important role in the dispersion, transport, photochemical reactions and formation of secondary air pollutants.

In this study, the effect of meteorological variables on different air pollutant concentrations has been analyzed using correlation analysis and graphical presentation in Makkah, Saudi Arabia during the month of Ramadan (20 July to 18 August, 2012), which is the busiest month of the year after the Hajj season.

PMio, had relatively weaker correlation with other air pollutants, most probably suggesting different sources of emission.

Among meteorological variables, as expected temperature showed strong positive correlation with ozone (0.74), and negative correlation with NOx, CO, S02, and PM10, whose concentrations are rather dependent on the emission sources.

Wind speed disperses local pollutants, which probably explains why it was negative correlation with NOx, S02 and CO, however it was positive correlation with ozone and PMIO, probably because higher wind speed encourages sand storms and resuspension of particles from roadsides and bared deserts and transport of ozone from the surrounding rural areas.

Relative humidity is positively correlated with PMIO and negatively correlated with the rest of the air pollutants.

The effect of rainfall was negligible because no rain occurred during the study period.

The effects of meteorological variables have also been analysed using polar plots and pollution roses, which provide further insight into the association between air pollutants and meteorology.

Factors responsible for the high concentrations during the PM10 episode from 26 to 28 July 2012 were analyzed.

Unexpectedly, atmospheric pressure and relative humidity seemed to be responsible for the episode, and not the sources of emissions, which are higher during the last 10 days of Ramadan (08 to 18 August).