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Daisen, Tottori Prefecture, Japan, occupies a unique and geographically significant position on the Sea of Japan coast. Situated at approximately 35.5°N, 133.5°E, the city’s landscape is dominated by Mount Daisen, an inactive stratovolcano and the highest peak in the San’in region. This imposing mountain range profoundly shapes Daisen’s microclimate and influences its air quality patterns. The city itself is nestled within a relatively narrow coastal plain, transitioning rapidly to steeper slopes as one moves inland. The Sea of Japan provides a moderating influence on temperatures, though it also contributes to high humidity and frequent fog, particularly during the autumn and winter months. Surrounding Daisen is a mosaic of agricultural land, primarily rice paddies and orchards, interspersed with small villages and forested areas. While Daisen isn't directly adjacent to major industrial belts, it lies within a region experiencing gradual urbanization, with nearby cities like Matsue exhibiting moderate industrial activity. The urban–rural gradient is relatively sharp, with Daisen retaining a distinctly rural character despite its status as a regional hub. The prevailing winds generally blow from the Sea of Japan towards the inland areas, carrying moisture and potentially pollutants from coastal industrial zones. The elevation, ranging from sea level to the peaks of Mount Daisen, creates complex terrain that can trap pollutants and influence local air circulation patterns, leading to localized variations in air quality. The surrounding landscape, a blend of agricultural fields, forests, and the imposing mountain, plays a crucial role in the city's overall environmental health.

Daisen’s air quality experiences a distinct seasonal cycle heavily influenced by its coastal location and mountainous terrain. Spring (March-May) generally sees improved air quality as temperatures rise and winds become more frequent, dispersing any accumulated pollutants. However, pollen levels from surrounding orchards can trigger respiratory sensitivities. Summer (June-August) is typically the cleanest period, with consistent sea breezes and occasional rainfall helping to scrub the atmosphere. The monsoon season brings periods of heavy rain, further reducing particulate matter. Autumn (September-November) presents a more complex picture. As temperatures cool, the likelihood of temperature inversions increases, particularly in the valleys surrounding Mount Daisen. These inversions trap pollutants near the ground, leading to periods of reduced visibility and potentially elevated levels of certain pollutants. Frequent fog, a characteristic feature of the Sea of Japan coast during autumn, exacerbates this issue by limiting atmospheric mixing. Winter (December-February) is often the most challenging season. Cold, stable air masses combined with frequent fog and temperature inversions create conditions conducive to pollutant accumulation. While industrial activity is relatively low, residential heating contributes to localized pollution. Sensitive groups, such as children, the elderly, and individuals with respiratory conditions, should limit prolonged outdoor exposure during these periods, especially in the mornings when inversions are most prevalent. Outdoor activities are generally best enjoyed during the summer months, taking advantage of the prevailing sea breezes and frequent rainfall. Careful monitoring of local weather conditions is advisable throughout the year, particularly during autumn and winter.