UV polarization lidar for remote sensing new particles formation in the atmosphere
Spotlight summary: Atmospheric aerosol particles worsen the air quality and reduce atmospheric visibility. According to WHO, air pollution is the biggest environmental health risk. On the other hand, aerosol particles have a net cooling effect on the climate, thus counteracting the increase in greenhouse gases. Secondary particle formation from precursor vapors, often called 'new particle formation', is a major source of ultrafine particles (<100 nm) and cloud condensation nuclei. New particle formation seems to occur all around the world in many different kinds of environments, both in the planetary boundary layer and in the free troposphere. It involves a complicated chain of reactions and processes, which are not yet understood in detail.
Detecting new particle formation is technically challenging, mainly due to the small size of the newly formed particles and low concentrations of the relevant precursor vapors. A range of in-situ measurement techniques have been developed in recent years, but observing new particle formation with remote sensing technology is still work in progress. Thus observations of new particle formation in the free troposphere have been limited to sporadic measurements at mountain locations or airplane campaigns.
David et al. present a step towards remote measurement of new particle formation. They tested by numerical simulations the optical requirements for a lidar to remotely detect new particle formation events. Lidars are backscattering instruments generally used to study the vertical profile of larger aerosol particles. They conclude that the lidar should operate in the UV spectral range and be polarization-resolved. Two case studies are analyzed, where the small spherical particles formed by new particle formation can be clearly distinguished from the larger non-spherical particles. However, in this study only new particle formation promoted by large non-spherical particles (e.g. desert dust or volcanic ash) is considered. For wider applicability, the work should be extended to all kinds of new particle formation events. Still, the proposed methodology shows promise for studying the vertical extent of new particle formation.
Technical Division: Information Acquisition, Processing, and Display
ToC Category: Remote Sensing and Sensors
|OCIS Codes:||(010.1110) Atmospheric and oceanic optics : Aerosols|
|(010.1290) Atmospheric and oceanic optics : Atmospheric optics|
|(010.3640) Atmospheric and oceanic optics : Lidar|
|(290.1310) Scattering : Atmospheric scattering|
|(290.1350) Scattering : Backscattering|
|(290.5855) Scattering : Scattering, polarization|
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