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Tianguá, nestled in the northern region of Ceará state, Brazil, occupies a unique geographic position within the broader Sertão landscape. Situated at coordinates -3.7322, -40.9917, the city’s terrain is characterised by gently undulating hills and plateaus, typical of the Brazilian Northeast. The elevation, while not substantial, contributes to localised microclimates. Tianguá isn’t directly coastal, lying approximately 70km inland from the Atlantic Ocean, but its climate is significantly influenced by maritime air masses, moderating the extreme heat common further inland. The surrounding landscape is predominantly Caatinga, a semi-arid scrubland, interspersed with areas of small-scale agriculture, primarily subsistence farming focused on crops like beans, corn, and cassava. While Tianguá isn’t a major industrial hub, regional economic activity centres around agriculture and livestock, with associated dust emissions. The urban-rural gradient is relatively sharp; the city itself is a concentrated area of population, quickly transitioning to sparsely populated rural areas. This proximity to agricultural lands and the prevailing wind patterns can contribute to the transport of particulate matter into the urban centre, impacting local air quality. The lack of significant natural barriers to wind flow means pollutants can disperse, but also be readily carried from surrounding areas.

Tianguá experiences a distinct wet and dry season, rather than traditional four seasons. Air quality in Tianguá is most compromised during the prolonged dry season, typically from August to December. This period sees minimal rainfall, leading to increased dust resuspension from agricultural lands and unpaved roads. Lower humidity also reduces the natural scavenging of pollutants from the atmosphere. Strong, dry winds exacerbate the issue, carrying particulate matter into the city. January to April marks the wet season, bringing significant improvements in air quality as rainfall effectively washes away accumulated pollutants. However, even during the wet season, localised pollution from vehicle emissions and small-scale burning of agricultural waste can occur. May to July represents a transitional period with moderate air quality. Temperature inversions, common during cooler nights throughout the year, can trap pollutants near ground level, worsening conditions. Sensitive groups – children, the elderly, and those with respiratory conditions – should limit strenuous outdoor activity during the peak of the dry season. Monitoring wind direction is crucial; periods with winds from agricultural areas are likely to see poorer air quality. Fog, occasionally occurring during the transitional months, can also trap pollutants.