Physicochemical properties of atmospheric particles at different altitude via tethered balloon system

Abstract:

The radiative forcing of the ambient aerosol is strongly influenced by the vertical distribution of aerosols. The estimation of the indirect effect of aerosol also has a significant uncertainty due to the spatial variation of the aerosol, especially at the cloud base. The unmanned systems have gained significant interest in atmospheric science, which could minimize the error, risk and cost in environmental research. Deployment of an unmanned aerial system such as ARM’s tethered balloon system can provide important information about the vertical profile of aerosol with longer temporal coverage. In this study, the tethered balloon system was deployed at the Southern Great Plains (SGP; DOE ARM mega site), Oklahoma, and Oliktok Point, Alaska (OLI site) collecting aerosol particles at different boundary layers. Particle samples were collected using a 4-stage cascade impactor. Particle samples were collected from different air-masses, from clean condition to polluted biomass burning plume. The morphology and chemical composition of individual particles were analyzed via multi-modal micro-spectroscopy techniques such as computer-controlled scanning electron microscopy with energy dispersive X-ray spectroscopy, transmission electron microscopy, scanning transmission X-ray microscopy, time-of-flight secondary ion mass spectrometry and Raman spectroscopy. Single particle composition results show the clear difference in aerosol compositions at various altitudes. Our analysis shows a considerably increase in sulfates at higher altitude than ground level. In general, we observed substantial amount of dust particles at higher altitude, suggesting the importance of supermicron size particles and their potential to influence atmospheric ice nucleation in mixed-phase clouds. We also observed super micron size carbonaceous particles at 800m altitude during a biomass burning event. The research can benefit in understanding the short-range, long-range transportation of atmospheric particles and vertical profile of atmospheric particle composition. The experiments performed via unmanned system could provide a long-term observation in atmospheric science efficiently and economically.