Fast time response measurements of particle size distributions in the 3–60 nm size range with the nucleation mode aerosol size spectrometer
<p>Earth's radiation budget is affected by new particle formation (NPF) and the growth of these nanometre-scale particles to larger sizes where they can directly scatter light or act as cloud condensation nuclei (CCN). Large uncertainties remain in the magnitude and spatiotemporal dis...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-06-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/11/3491/2018/amt-11-3491-2018.pdf |
| Summary: | <p>Earth's radiation budget is affected by new particle
formation (NPF) and the growth of these nanometre-scale particles to larger
sizes where they can directly scatter light or act as cloud condensation
nuclei (CCN). Large uncertainties remain in the magnitude and spatiotemporal
distribution of nucleation (less than 10 nm diameter) and Aitken (10–60 nm
diameter) mode particles. Acquiring size-distribution measurements of these
particles over large regions of the free troposphere is most easily
accomplished with research aircraft.</p><p>We report on the design and performance of an airborne instrument, the
nucleation mode aerosol size spectrometer (NMASS), which provides
size-selected aerosol concentration measurements that can be differenced to
identify aerosol properties and processes or inverted to obtain a full size
distribution between 3 and 60 nm. By maintaining constant downstream
pressure the instrument operates reliably over a large range of ambient
pressures and during rapid changes in altitude, making it ideal for aircraft
measurements from the boundary layer to the stratosphere.</p><p>We describe the modifications, operating principles, extensive calibrations,
and laboratory and in-flight performance of two NMASS instruments operated
in parallel as a 10-channel battery of condensation particle counters (CPCs)
in the NASA Atmospheric Tomography Mission (ATom) to investigate NPF and
growth to cloud-active sizes in the remote free troposphere. An inversion
technique to obtain size distributions from the discrete concentrations of
each NMASS channel is described and evaluated.</p><p>Concentrations measured by the two NMASS instruments flying in parallel are
self-consistent and also consistent with measurements made with an optical
particle counter. Extensive laboratory calibrations with a range of particle
sizes and compositions show repeatability of the response function of the
instrument to within 5–8 % and no sensitivity in sizing performance to
particle composition. Particle number, surface area, and volume
concentrations from the data inversion are determined to better than 20 %
for typical particle size distributions. The excellent performance of the
NMASS systems provides a strong analytical foundation to explore NPF around
the globe in the ATom dataset.</p> |
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| ISSN: | 1867-1381 1867-8548 |