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Dingxi occupies a strategic position in central Gansu province, situated on the eastern edge of the Loess Plateau where it transitions toward the Qinling Mountains. This city of 2.5 million people lies at approximately 1,900 meters elevation in the upper reaches of the Wei River basin, creating a distinctive urban character shaped by its semi-arid highland environment. The surrounding landscape features deeply eroded loess hills and terraced agricultural lands, with the city itself positioned in a valley that channels both air masses and human activity. Dingxi's location places it within China's 'Loess Plateau Agricultural Zone,' where extensive farming of potatoes, grains, and medicinal herbs creates seasonal dust and biomass burning emissions. The urban-rural gradient is pronounced, with the compact urban core surrounded by vast agricultural hinterlands that influence air quality through both natural and anthropogenic processes. Proximity to the Yellow River's tributaries provides some moisture but no significant bodies of water to moderate pollution dispersion. The city's position along transportation corridors connecting Lanzhou to eastern China means it experiences transit-related emissions, while its valley setting frequently traps pollutants under temperature inversion conditions, particularly during calm winter periods when heating demands peak in this cold highland climate.

Dingxi's air quality follows a distinct seasonal rhythm shaped by its highland continental climate and agricultural cycles. Winter (December-February) brings the most challenging conditions, with frequent temperature inversions trapping pollutants from residential heating (primarily coal and biomass) in the valley basin. Cold, stagnant air combines with occasional fog to create persistent haze, making these months particularly problematic for respiratory health. Spring (March-May) sees gradual improvement as temperatures rise and winds increase, though March and April experience periodic dust storms as strong winds lift loess soil from surrounding farmlands during planting preparation. Summer (June-August) offers the cleanest air, with monsoon-influenced rainfall washing pollutants from the atmosphere and consistent valley breezes providing natural ventilation. However, occasional biomass burning from agricultural residue can create short-term spikes. Autumn (September-November) begins with relatively good conditions but deteriorates in late October and November as heating season commences and atmospheric stability increases. Sensitive groups should minimize outdoor activity during winter mornings when inversions are strongest and during spring dust events. The optimal period for outdoor activities extends from June through September, when natural ventilation and precipitation combine to provide the most favorable breathing conditions in this highland city.