Vertical Distribution Shapes of Dust Aerosol and the Relation with Atmospheric Condition

Vertical distribution of aerosols under different atmospheric conditions in the free troposphere is directly observed using surface micro-pulse lidar and microwave radiometer TP/WVP-3000 at the Semi-Arid Climate & Environment Observatory of Lanzhou University (SACOL, 35.95°N, 104.1°E) in the west of the Loess Plateau, China in Spring of 2008. The study shows that the aerosol vertical distribution with altitude increasing has three shapes: a single peak under stable atmospheric conditions and free sand effects, an exponential decrease under unstable atmospheric conditions and sand storm stages, and slight change in the mixed layer and at the first and last stage of sand storm process. Due to the impact of the top atmospheric boundary, diurnal variation of aerosol extinction coefficient shows a single peak, which is higher in the afternoon and lower in the morning. Observations from SACOL show that aerosol extinction coefficient in the layers with altitude below and above 1 km is positively and negatively correlated to the relative atmospheric humidity, respectively, suggesting that water soluble chemicals are mixed with aerosol in the altitude below but not above 1 km during sandstorm process.