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Algiers, the capital of Algeria, occupies a dramatic coastal position on the Mediterranean Sea's southern shore, nestled between the Sahel Hills to the west and the rugged Tell Atlas mountains to the east and south. This strategic location at 36.7325°N, 3.0872°E places it at the heart of North Africa's Maghreb region, with the city sprawling across steep slopes that rise from sea level to elevations exceeding 400 meters in the Casbah district, creating a distinctive urban topography. The Mediterranean coastline provides a natural harbour, but the surrounding mountainous terrain acts as a partial barrier to inland air circulation, potentially trapping pollutants in the urban basin. Algiers functions as Algeria's primary economic and administrative hub, with industrial zones concentrated in the eastern suburbs like Rouïba and Réghaïa, while agricultural belts lie further inland in the Mitidja Plain. The urban-rural gradient is sharp, with dense, historic neighbourhoods giving way to modern developments and peri-urban sprawl. This geography influences air quality through sea breezes that can disperse emissions but also through temperature inversions in the cooler months, where cold air gets trapped by the hills, exacerbating pollution from vehicles, industry, and residential heating. The city's proximity to the Sahara Desert, though buffered by the Atlas range, means occasional dust intrusions add particulate matter, blending urban and natural pollutants in a complex atmospheric mix.

In Algiers, air quality follows a distinct seasonal rhythm shaped by Mediterranean climate patterns. Winter, from December to February, sees the worst pollution due to temperature inversions—cold, stagnant air gets trapped in the city's basin by surrounding hills, concentrating emissions from heating systems and traffic. Sensitive groups like asthmatics should limit outdoor exertion on calm, foggy mornings. Spring, from March to May, brings improvement as rising temperatures and increased winds, including the southerly Sirocco from the Sahara, disperse pollutants, though dust storms can spike particulate levels; this is a favourable time for outdoor activities. Summer, from June to August, offers the cleanest air overall, with consistent sea breezes and low humidity flushing out contaminants, but high ozone levels may form on hot, sunny days from vehicle emissions, posing risks for children and the elderly during peak afternoon hours. Autumn, from September to November, sees a gradual decline as winds weaken and rainfall increases, washing away some pollutants but also leading to occasional stagnation; by late autumn, pollution begins to build again. Throughout the year, avoid outdoor exercise during peak traffic hours, especially in winter, and monitor local advisories for dust events or industrial emissions.