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Antsahavaribe, nestled within the Antsiranana (Diego Suarez) region of northern Madagascar, presents a unique geographic context influencing its air quality. The city sits at a relatively low elevation, approximately 20 meters above sea level, close to the Indian Ocean and the expansive Bay of Antsiranana. This coastal proximity introduces significant humidity and salt spray, impacting particulate matter composition. The surrounding landscape is characterised by a transition from coastal plains to rolling hills and the Tsaratanana Massif further inland. While not heavily industrialised, Antsiranana is a crucial port city, handling significant cargo traffic, including fuels and minerals, which contributes to localised emissions. Agriculture, particularly vanilla and ylang-ylang cultivation, dominates the rural areas surrounding Antsaharibe, with potential for seasonal burning impacting air quality. The urban-rural gradient is relatively sharp, with a quick transition from densely populated areas to agricultural land. The prevailing winds, influenced by the southeast trade winds, play a crucial role in dispersing or concentrating pollutants. Topography channels winds through the bay, potentially creating localised stagnation points. The city’s location within a tropical climate means consistent warmth and high humidity, affecting pollutant dispersion and chemical reactions in the atmosphere. This combination of factors creates a complex air quality profile.

Antsahavaribe experiences a distinct wet and dry season, heavily influencing air quality. The dry season, roughly from May to October, sees a peak in particulate matter due to increased dust from unpaved roads and agricultural activities. Lower humidity allows for greater suspension of these particles. The southeast trade winds, while generally dispersing pollutants, can also carry dust from inland areas. November marks the transition, with sporadic rainfall beginning to settle dust. The wet season, from November to April, generally brings improved air quality as rainfall effectively washes away pollutants. However, increased humidity can promote the formation of mould and other biological pollutants indoors. January and February, the peak of the rainy season, typically offer the freshest air. Temperature inversions, though less frequent than in temperate climates, can occur during calmer periods, trapping pollutants near the ground. The port activity remains consistent throughout the year, contributing a baseline level of emissions. Sensitive individuals, such as those with respiratory conditions, should be particularly cautious during the dry season and monitor their health. Avoiding strenuous outdoor activity during peak dust periods is advisable. The consistent warmth means pollutants react differently than in colder climates, potentially forming secondary pollutants.