Data from: Ultrafine aerosol formation and growth in a southern California desert

Ultrafine aerosol number-size distributions were collected in the
northwestern Sonoran Desert from January 2018 to April 2019 to
assess the frequency and intensity of particle formation and
growth events in this region. Daily and seasonal patterns of
particle formation and growth events were compared with meteorology,
ozone mixing ratios, air mass back-trajectories, and modeled
boundary layer height to determine potential environmental and
anthropogenic influences. These were supplemented with
measurements of gas-phase biogenic volatile organic
compounds (BVOCs) during a period of active particle formation to
gather insights into the potential role of condensation of highly
oxidized organic molecules. Particle formation peaked in summer,
trending with dominant westerly winds crossing the
southern California megalopolis with correspondingly high ozone,
higher peak solar radiation, and greater variability in planetary
boundary layer height. The timing of the start of growth events
corresponded to abrupt increases in both modeled
planetary boundary layer height and measured solar radiation.
Formation and/or growth events occurred on 22% of days with an
average observed diameter growth rate of 5.2 ± 2.2 nm/hr.
Gas-phase measurements of BVOCs suggest a
low-isoprene, high-monoterpene environment that, when combined
with high ozone, creates ideal conditions for aerosol formation.
These observations indicate that the formation and growth of
ultrafine particles is common in this California desert atmosphere and
is likely influenced by the products of anthropogenic pollutants
and biogenic emissions.