Fig. 1. Schematic of LP-DOAS structure and measurement process

Fig. 2. Comparison of NO₂, O₃, and SO₂ concentration measured by LP-DOAS and at the station. (a) NO₂; (b) O₃; (c) SO₂; (d) relative deviation

Fig. 3. Diurnal variation of concentration of NO₂, O₃, and SO₂. (a) NO₂; (b) O₃; (c) SO₂

Fig. 4. Weekly variation of NO₂ concentration and the relationship with the traffic flow during morning rush hour

Fig. 5. Monthly variation of concentration of three gases. (a) NO₂; (b) O₃; (c) SO₂

Fig. 6. Relationship among the traffic flow and the NO₂, O₃, and SO₂ concentrations