Tropospheric ozone (O₃) and peroxyacetyl nitrate (PAN) are both photochemical pollutants harmful to the ecological environment and human health, especially in the Tibetan Plateau (TP). However, the factors determining their variations in the TP have not been comprehensively investigated. Results from field measurements and observation-based models revealed that day-to-day variations in O₃ and PAN were in fact controlled by distinct physiochemical processes.