Persistent influence of dust on aerosol properties in summer over the northeast Tibetan Plateau explored by surface and tethered balloon-borne observations

Abstract

Aerosol properties over the Tibetan Plateau exert important impacts on weather and climate in this area and downstream regions. The influence of dust on aerosol properties over this region has been demonstrated by previous studies based on remote sensing. However, there is still a lack of knowledge regarding how aerosol properties were influenced by dust and the evolution of dust events, especially in a temporally and vertically resolved way. In this study, aerosol microphysical and optical properties in summer were investigated by in-situ surface and tethered-balloon borne observations, which were also utilized to explore dust events with a joint analysis of the MERRA-2 reanalysis data and HYSPLIT backward trajectories. The PM₁/PM₁₀ ratios and scattering Ångström exponents were found to be quite low at most of the time during the campaign even in the absence of dust events, evidently suggesting that surface aerosol properties were persistently influenced by dust. Particle mass size distributions in the free troposphere also clearly revealed fingerprints of dust. An examination on individual dust event indicated that dust particles could be of local origins or long-range transported from deserts to the north of the plateau. This study helps improve our understanding on the influence of dust on aerosol properties, possible sources of observed dust particles and the evolution of dust events over this region. A future effort is worth undertaking to address potential impacts of dust-influenced aerosol properties on atmospheric processes of climatic importance by integrating various observations and model simulations.