Cable-car measurements of vertical aerosol profiles impacted by mountain-valley breezes in Lushan Mountain, East China

Abstract In-situ field observations of vertical aerosol profiles for one month in complex terrain (Lushan Mountain, China) were carried out using a cable car, which resolved detailed vertical distributions of mountain aerosols with low-cost operation. Cable-car observations were conducted during the early morning and late afternoon, when mountain and valley winds dominated, respectively. The diurnal aerosol variations at the top and foot of Lushan Mountain were analyzed based on environmental and meteorological stations. The observations indicated that the mountain-valley breezes notably impacted the mountain-area aerosol distribution under weak weather conditions. More uniform aerosol profiles for the afternoon than the morning, with their decreasing rates of PM2.5 (particles with diameters less than 2.5 μm) were 2.28 and 1.64 μg m−3/100 m, respectively. The PM2.5/PM10 ratio at the mountain top increased from 0.69 to 0.81, and that at the mountain base decreased from 0.75 to 0.70 from morning to afternoon. The PM2.5 concentration decreased in and around Lushan Mountain from daytime to nighttime, with the impacted diameter of the 300-m topography line being smaller than ~5 km, while the concentration increased in Jiujiang City. The relative decreasing rate of PM2.5 was higher at the mountain top site (~20%) than at the base site (~2%) from daytime to nighttime. Moreover, uniform aerosol profiles could have been caused by regional transport through a relatively strong low-level synoptic flow (~5 m s-1) and the mountain's dynamic lifting effect.