The mountain that makes its weather
Lushan Mountain, a massif rising to 1,474 meters at its highest peak, is an isolated barrier in the humid subtropical climate of Jiangxi province. Its position south of the Yangtze River and west of Poyang Lake—China's largest freshwater lake—provides a constant source of moisture. As warm, moist air from the plains is forced upwards by the mountain's steep slopes, it cools and condenses, a process known as orographic lift. This effect generates a persistent "sea of clouds" and a remarkable microclimate where fog occurs on an average of 196 days per year.
The Lushan Meteorological Bureau, established in 1954, sits on the mountain and is a national reference climatological station. For decades, scientists here have studied the unique atmospheric conditions. The mountain is one of six observation sites for a cloud-fog testing station run by the Chinese Academy of Meteorological Sciences, providing a natural laboratory for understanding cloud physics. Researchers have collected vast amounts of data on cloud microphysics, including over 2,400 samples and more than 5,000 measurements of raindrop size distribution. These studies help explain the formation of the mountain's frequent drizzles and the specific properties of its dense fogs.
A forest sustained by fog
The frequent fog is a scenic feature and a direct water source for the mountain's ecosystem. The process, called horizontal precipitation or fog deposition, allows vegetation to "comb" moisture directly from the air. Conifers and other trees with high leaf surface area are particularly efficient at this, capturing tiny cloud droplets that then drip to the forest floor, supplementing rainfall. This is an important water input for the mixed evergreen and deciduous broadleaf forests found at elevations between 700 and 1,000 meters.
The Lushan Botanical Garden, founded in 1934, is China's first subtropical mountain botanical garden and is central to this research. Within its 300-hectare area, scientists study how different plant species utilize various water sources. Isotope analysis of xylem water in local pine (Pinus massoniana and Pinus taiwanensis) and oak species (Quercus variabilis and Quercus serrata) reveals how they shift their water uptake between rainfall, soil moisture, and fog. The garden itself has over 5,000 plant taxa, including a major collection of over 200 species of gymnosperms and 96 rare or endangered species.