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Kurihara, Miyagi Prefecture, Japan, occupies a geographically diverse landscape nestled between the Pacific coast and the foothills of the Ou Mountains. Located at approximately 38.73°N, 141.02°E, the city’s terrain is characterized by a gradual transition from coastal plains to rolling hills and steeper slopes further inland. This varied topography significantly influences local air circulation patterns. The city sits within the Sendai Plain, a fertile agricultural region, and benefits from proximity to the Pacific Ocean, which moderates temperatures but can also introduce marine aerosols. To the west, the Ou Mountains act as a barrier, potentially trapping pollutants under certain meteorological conditions. Kurihara’s urban character is a blend of traditional Japanese settlements and modern residential areas, reflecting its history as an agricultural hub transitioning towards a more diversified economy. While not a major industrial center, the surrounding region includes agricultural zones cultivating rice and other crops, and some light industrial activity in nearby towns. The urban–rural gradient is relatively smooth, with agricultural land interspersed throughout the city limits. Elevation varies considerably, ranging from near sea level along the coast to several hundred meters in the western, mountainous areas. This elevation change impacts air quality; cooler air tends to settle in valleys, potentially concentrating pollutants, while higher elevations experience greater dispersion. The prevailing winds, generally from the east and southeast, play a crucial role in transporting air masses and influencing local air quality, often bringing in moisture from the Pacific.

Kurihara’s air quality experiences a distinct seasonal cycle dictated by its climate and prevailing weather patterns. Spring (March-May) sees a gradual improvement as temperatures rise and winds increase, dispersing accumulated winter pollutants. However, pollen season significantly impacts air quality, triggering respiratory sensitivities for many residents. Summer (June-August) is generally the cleanest period, with frequent sea breezes and occasional typhoons that effectively flush out pollutants. The monsoonal influence brings consistent winds, preventing stagnation. Autumn (September-November) marks a transition period; while winds remain relatively strong initially, the onset of cooler temperatures can lead to occasional temperature inversions, particularly in valleys, trapping pollutants closer to the ground. These inversions are more likely in October and November. Winter (December-February) presents the most challenging period for air quality. Cold, stable air masses often settle in the valleys, creating temperature inversions that trap pollutants. Reduced wind speeds and increased humidity contribute to stagnant air conditions. Fog, common during winter mornings, further exacerbates the problem by limiting dispersion. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should limit outdoor activity during prolonged periods of fog or temperature inversions, especially in the mornings. Maintaining indoor air quality through ventilation and air purification can also be beneficial. While summer offers the best conditions for outdoor recreation, spring and autumn require careful monitoring of weather forecasts and awareness of potential air quality impacts.