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Guli, situated in Zhejiang Province's central region at coordinates 28.9000°N, 120.0333°E, occupies a strategic position within China's Yangtze River Delta economic powerhouse. This mid-sized city of 723,490 residents lies approximately 200 kilometers southwest of Shanghai, nestled in the transition zone between the coastal plains and the inland hills of eastern Zhejiang. The terrain slopes gently from northwest to southeast, with elevations ranging from 50 to 200 meters above sea level, creating a natural basin effect that can trap pollutants. Guli's location places it within the Jinqu Basin, surrounded by the Dapan Mountains to the west and the Kuocang Mountains to the east, which form partial barriers to atmospheric circulation. The city sits approximately 80 kilometers inland from the East China Sea, with the Ou River system flowing through the region, providing some moderating influence on local climate. Guli exists within Zhejiang's mixed industrial-agricultural belt, where light manufacturing, textile production, and electronics assembly facilities intermix with rice paddies and tea plantations in the surrounding countryside. The urban-rural gradient shows compact urban development concentrated along transportation corridors, gradually giving way to agricultural land and forested hills. This geographic configuration creates complex air quality dynamics, with local emissions from urban activities mixing with regional transport of pollutants from the Yangtze River Delta megacity cluster, while the surrounding mountains can create stagnation conditions during certain weather patterns.

Guli experiences distinct seasonal air quality patterns shaped by East Asian monsoonal circulation and local topography. During winter (December-February), cold, dry northerly winds from the Siberian High transport pollutants from northern industrial regions, while temperature inversions frequently develop in the basin, trapping emissions near the surface. This creates the year's worst air quality, particularly in January when heating demands increase and atmospheric mixing is minimal. Sensitive groups should limit prolonged outdoor exposure during these months. Spring (March-May) brings transitional conditions with increasing rainfall that helps cleanse the atmosphere, though occasional dust events from northern China can temporarily degrade air quality. The optimal period for outdoor activities arrives in late spring (May) when temperatures moderate and precipitation increases. Summer (June-August) features the East Asian summer monsoon with southeasterly winds from the ocean bringing cleaner maritime air, though high temperatures can accelerate ozone formation on sunny days. Autumn (September-November) begins with relatively good air quality as monsoon circulation weakens, but conditions gradually deteriorate through November as winter patterns establish. Fog becomes more frequent in late autumn and winter, sometimes mixing with pollution to create haze episodes. Residents with respiratory conditions should monitor daily forecasts closely during transitional months and consider indoor air purification during peak pollution periods.