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Meishan, nestled in the Chiayi County of Taiwan, occupies a geographically significant position within the island's central mountain range. Located at approximately 23.56°N, 120.63°E and an elevation averaging around 830 meters (2723 feet), the city enjoys a unique microclimate shaped by its mountainous terrain. The surrounding landscape is dominated by lush, subtropical forests and terraced farmlands, a testament to the region's agricultural heritage. Meishan sits on the western slopes of Mount Nanhua, the highest peak in Chiayi County, influencing local wind patterns and precipitation. The city’s proximity to the Taiwan Strait, though not directly coastal, still experiences maritime influences, particularly regarding humidity and occasional sea breezes. The urban fabric of Meishan is relatively compact, characterized by a blend of traditional Taiwanese architecture and modern developments, reflecting its evolving role as a regional agricultural hub and tourist destination. The surrounding area exhibits a clear urban-rural gradient, transitioning from the built environment of Meishan to extensive tea plantations and fruit orchards. Downstream, towards the coastal plains, lies a broader agricultural belt. This topography and surrounding land use significantly impact air quality; the mountains can trap pollutants, while agricultural activities contribute to particulate matter and volatile organic compounds, especially during harvest seasons. The elevation also influences temperature inversions, a key factor in air pollution episodes.

Meishan’s air quality follows a distinct seasonal pattern dictated by Taiwan’s subtropical climate and monsoon influences. The wet season, typically spanning May to September, generally sees improved air quality due to frequent rainfall that washes away pollutants and increased wind speeds dispersing them. However, typhoons can occasionally bring dust and debris from the mainland. October to March constitutes the drier season, and this period often presents the greatest air quality challenges. During these months, temperature inversions are more prevalent, particularly in November and December, trapping pollutants close to the ground. These inversions occur when a layer of warm air sits above cooler air, preventing vertical mixing. Agricultural burning, a common practice in surrounding rural areas to clear fields for the next planting season, significantly contributes to particulate matter pollution during this time. Fog, common in the cooler months, further exacerbates the issue by reducing visibility and trapping pollutants. Spring (March-April) sees a gradual improvement as temperatures rise and winds increase. Summer (June-August) is generally the cleanest period, although typhoon season introduces its own set of air quality concerns. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the drier months, particularly when agricultural burning is occurring. Outdoor activities are best planned for the wetter months or early mornings when winds are typically stronger.