A theoretical study of diurnal variations of NO2 concentrations in the air is conducted to verify the observations at the Manila Observatory inside the Ateneo de Manila Campus (Quezon City, Philippines) in June and August 2002. The analysis of the observations shows that the average concentration in August is greater than in June. The average time variation is semi-diurnal with a major maximum in the evening and a slight maximum in the morning. The daily variations may be classified into four types of diurnal variations according to the occurrence of maxima in the concentrations. A simple fluid dynamical model is formulated in order to explain the occurrence of these types. Integrations of the model indicate that the types can be explained primarily in terms of the horizontal transport of pollutants due to local winds.
[Presented at the Samahang Pisika ng Pilipinas (SPP) Congress, 2004.]