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Shulan is a county-level city in central Jilin Province, situated approximately 120 kilometers northeast of Changchun, the provincial capital, within the Songliao Plain region of Northeast China. The city occupies a strategic position at the confluence of the Songhua River basin and the Changbai Mountain foothills, creating a distinctive urban-rural gradient where agricultural lands transition into modest urban development. At an elevation of around 200 meters above sea level, Shulan's terrain is predominantly flat with gentle undulations, characteristic of the Songnen Plain, though it slopes gradually toward the eastern mountainous areas. This location places Shulan within Jilin's agricultural heartland, surrounded by extensive corn and soybean fields that contribute to seasonal biomass burning emissions. The city lies near several smaller rivers, including the Shulan River, but lacks major water bodies that might significantly influence local air circulation patterns. Proximity to industrial zones in nearby cities like Jilin City and Changchun means Shulan experiences transported pollution, particularly during prevailing northwesterly winds. The urban fabric itself features typical medium-density development with some light manufacturing, creating localized emissions that combine with regional agricultural and industrial sources. This geographic positioning in a basin-like plain, flanked by mountains to the east, occasionally traps pollutants under stable atmospheric conditions, particularly during winter temperature inversions, while summer monsoon flows from the southeast provide some cleansing effects.

Shulan's air quality follows a distinct seasonal pattern shaped by Northeast China's continental monsoon climate. Winter (December-February) brings the worst pollution as coal-fired heating systems operate at full capacity, combining with frequent temperature inversions that trap emissions near the surface. Cold, stagnant air masses create persistent haze, making January particularly problematic for outdoor activities. Sensitive groups should limit exposure during these months and use air purifiers indoors. Spring (March-May) sees gradual improvement as heating demand decreases, though March and April can experience dust storms from Mongolia and local agricultural burning, causing sporadic spikes. Windy conditions help disperse pollutants but bring particulate matter. Summer (June-August) offers the cleanest air with the East Asian monsoon bringing southeasterly winds and precipitation that scrub the atmosphere. July and August are optimal for outdoor activities, though occasional high humidity can trap ozone precursors. Autumn (September-November) begins with relatively good conditions in September but deteriorates in October as heating season commences and agricultural residue burning peaks after harvest. Temperature inversions return in November, creating a transition to winter haze. Throughout the year, sensitive individuals should monitor daily conditions, avoid morning outdoor exercise during pollution episodes, and plan major outdoor activities for summer months when dispersion is most favorable.