2 research outputs found
Parameterized Yields of Semivolatile Products from Isoprene Oxidation under Different NO<sub><i>x</i></sub> Levels: Impacts of Chemical Aging and Wall-Loss of Reactive Gases
We
developed a parametrizable box model to empirically derive the
yields of semivolatile products from VOC oxidation using chamber measurements,
while explicitly accounting for the multigenerational chemical aging
processes (such as the gas-phase fragmentation and functionalization
and aerosol-phase oligomerization and photolysis) under different
NO<sub><i>x</i></sub> levels and the loss of particles and
gases to chamber walls. Using the oxidation of isoprene as an example,
we showed that the assumptions regarding the NO<sub><i>x</i></sub>-sensitive, multigenerational aging processes of VOC oxidation
products have large impacts on the parametrized product yields and
SOA formation. We derived sets of semivolatile product yields from
isoprene oxidation under different NO<sub><i>x</i></sub> levels. However, we stress that these product yields must be used
in conjunction with the corresponding multigenerational aging schemes
in chemical transport models. As more mechanistic insights regarding
SOA formation from VOC oxidation emerge, our box model can be expanded
to include more explicit chemical aging processes and help ultimately
bridge the gap between the process-based understanding of SOA formation
from VOC oxidation and the bulk-yield parametrizations used in chemical
transport models
Convolutional Neural Networks Facilitate Process Understanding of Megacity Ozone Temporal Variability
Ozone pollution is profoundly modulated
by meteorological
features
such as temperature, air pressure, wind, and humidity. While many
studies have developed empirical models to elucidate the effects of
meteorology on ozone variability, they predominantly focus on local
weather conditions, overlooking the influences from high-altitude
and broader regional meteorological patterns. Here, we employ convolutional
neural networks (CNNs), a technique typically applied to image recognition,
to investigate the influence of three-dimensional spatial variations
in meteorological fields on the daily, seasonal, and interannual dynamics
of ozone in Shenzhen, a major coastal urban center in China. Our optimized
CNNs model, covering a 13° × 13° spatial domain, effectively
explains over 70% of daily ozone variability, outperforming alternative
empirical approaches by 7 to 62%. Model interpretations reveal the
crucial roles of 2-m temperature and humidity as primary drivers,
contributing 16% and 15% to daily ozone fluctuations, respectively.
Regional wind fields account for up to 40% of ozone changes during
the episodes. CNNs successfully replicate observed ozone temporal
patterns, attributing −5–6 μg·m–3 of interannual ozone variability to weather anomalies. Our interpretable
CNNs framework enables quantitative attribution of historical ozone
fluctuations to nonlinear meteorological effects across spatiotemporal
scales, offering vital process-based insights for managing megacity
air quality amidst changing climate regimes