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Gomīshān, nestled within the Golestān Province of northern Iran, occupies a geographically complex and strategically important position. Located at approximately 37.07° N, 54.07° E, the city sits within the broader Caspian Hyrcanian mixed forests ecoregion, a unique temperate rainforest extending along the southern coast of the Caspian Sea. The terrain is characterized by rolling hills and valleys, transitioning from the coastal plains to the foothills of the Alborz Mountains. Gomīshān’s elevation, while moderate, contributes to localized microclimates and influences air circulation patterns. The proximity to the Caspian Sea is a defining feature, impacting humidity levels and prevailing winds, often bringing moisture-laden air inland. The surrounding landscape is predominantly agricultural, with extensive rice paddies and orchards dominating the rural areas. This agricultural activity, while vital to the regional economy, can contribute to seasonal particulate matter emissions, particularly during harvest periods. To the east, the landscape gradually rises towards the Alborz range, creating a barrier that can trap pollutants under certain meteorological conditions. The urban–rural gradient is relatively sharp, with Gomīshān acting as a regional hub for agricultural processing and trade, drawing in rural populations and generating associated industrial activity. The city’s location within a fertile river valley, coupled with its position as a transportation node, makes it susceptible to both natural and anthropogenic influences on air quality, demanding careful environmental management.

Gomīshān’s air quality experiences a distinct seasonal cycle heavily influenced by its Caspian Sea proximity and surrounding topography. Winters (December-February) are typically characterized by cooler temperatures and increased humidity, frequently accompanied by dense fog. This fog, combined with temperature inversions – where a layer of warm air traps cooler air near the ground – significantly exacerbates air pollution, trapping emissions from agricultural burning and limited industrial activity. The lack of strong winds during this period further compounds the issue. Spring (March-May) brings a gradual improvement as temperatures rise and winds increase, dispersing pollutants. However, agricultural activities, including the burning of crop residues after the rice harvest, can still contribute to elevated particulate matter levels in early spring. Summers (June-August) generally offer the best air quality, with warmer temperatures promoting atmospheric mixing and frequent sea breezes that help to ventilate the region. However, occasional heatwaves can lead to stagnant air conditions. Autumn (September-November) sees a return to more challenging conditions. As temperatures cool, the potential for temperature inversions increases, and agricultural burning resumes, leading to a noticeable decline in air quality. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during winter and autumn months, limiting outdoor exertion and monitoring local air quality information. Maintaining indoor air quality through ventilation and air purification can also be beneficial during periods of elevated pollution.