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Wake, Okayama Prefecture, Japan, occupies a geographically significant position within the Seto Inland Sea region. Situated at approximately 34.8028° N, 134.1575° E, the city’s terrain is characterized by gentle slopes rising from the plains towards the foothills of the Chūgoku Mountains to the north. This topography influences local air circulation patterns, potentially trapping pollutants under certain meteorological conditions. Wake lies within a predominantly agricultural landscape, surrounded by rice paddies and orchards, a typical feature of Okayama’s rural character. The proximity to the Seto Inland Sea, a relatively shallow body of water, moderates temperatures and introduces a maritime influence, though it can also contribute to humidity and fog formation, impacting pollutant dispersion. While not directly adjacent to major industrial belts, Wake benefits from its location within a broader regional economic zone, with connections to industrial areas further inland. The urban–rural gradient is gradual, with the city seamlessly blending into the surrounding agricultural areas, minimizing sharp boundaries. Elevation varies slightly within Wake, generally ranging from around 10 to 50 meters above sea level. The surrounding landscape is dominated by cultivated fields and scattered woodlands, contributing to a relatively low background level of particulate matter compared to more heavily industrialized areas. The prevailing winds, generally southwesterly, play a crucial role in transporting air masses and influencing the city’s air quality, often bringing in cleaner air from the sea.

Wake’s air quality experiences a distinct seasonal cycle dictated by Japan’s monsoon climate. Spring (March-May) sees a gradual improvement as temperatures rise and the East Asian monsoon begins to shift, bringing cleaner, drier air from the Pacific. However, early spring can still experience lingering fog, particularly in the mornings, which can trap pollutants close to the ground. Summer (June-August) is generally the cleanest period, with strong southwesterly winds dispersing any accumulated pollutants. The humid conditions, however, can exacerbate respiratory issues for sensitive individuals. Autumn (September-November) marks a transition period, with the weakening of the monsoon and the potential for temperature inversions, especially during calmer periods. These inversions trap cooler air near the surface, preventing vertical mixing and leading to pollutant accumulation. This is often the period with the highest potential for reduced air quality. Winter (December-February) is characterized by cold, stable air and frequent fog, particularly in the early morning hours. These conditions can significantly reduce visibility and trap pollutants, creating localized air quality concerns. Sensitive groups, including children, the elderly, and those with respiratory conditions, should exercise caution during autumn and winter mornings, limiting outdoor activity during periods of fog or stagnant air. The agricultural practices in the surrounding areas, such as burning of rice straw after harvest, can also contribute to localized pollution events, particularly in autumn.