Abstract. Surface solar radiation (SSR) observations have indicated an increasing trend
in Europe since the mid-1980s, referred to as solar “brightening”. In this
study, we used the regional air quality model, CAMx (Comprehensive Air
Quality Model with Extensions) to simulate and quantify, with various
sensitivity runs (where the year 2010 served as the base case), the effects
of increased radiation between 1990 and 2010 on photolysis rates (with the
PHOT1, PHOT2 and PHOT3 scenarios, which represented the radiation in 1990)
and biogenic volatile organic compound (BVOC) emissions (with the BIO
scenario, which represented the biogenic emissions in 1990), and their
consequent impacts on summer surface ozone concentrations over Europe between
1990 and 2010. The PHOT1 and PHOT2 scenarios examined the effect of doubling
and tripling the anthropogenic PM2.5 concentrations, respectively, while
the PHOT3 investigated the impact of an increase in just the sulfate
concentrations by a factor of 3.4 (as in 1990), applied only to the
calculation of photolysis rates. In the BIO scenario, we reduced the 2010 SSR
by 3 % (keeping plant cover and temperature the same), recalculated the
biogenic emissions and repeated the base case simulations with the new
biogenic emissions. The impact on photolysis rates for all three scenarios
was an increase (in 2010 compared to 1990) of 3–6 % which resulted in
daytime (10:00–18:00 Local Mean Time – LMT) mean surface ozone differences
of 0.2–0.7 ppb (0.5–1.5 %), with the largest hourly difference rising
as high as 4–8 ppb (10–16 %). The effect of changes in BVOC emissions
on daytime mean surface ozone was much smaller (up to 0.08 ppb,
∼ 0.2 %), as isoprene and terpene (monoterpene and sesquiterpene)
emissions increased only by 2.5–3 and 0.7 %, respectively. Overall, the
impact of the SSR changes on surface ozone was greater via the effects on
photolysis rates compared to the effects on BVOC emissions, and the
sensitivity test of their combined impact (the combination of PHOT3 and BIO
is denoted as the COMBO scenario) showed nearly additive effects. In addition, all
the sensitivity runs were repeated on a second base case with increased
NOx emissions to account for any potential underestimation
of modeled ozone production; the results did not change significantly in
magnitude, but the spatial coverage of the effects was profoundly extended.
Finally, the role of the aerosol–radiation interaction (ARI) changes in the
European summer surface ozone trends was suggested to be more important when
comparing to the order of magnitude of the ozone trends instead of the total
ozone concentrations, indicating a potential partial damping of the effects
of ozone precursor emissions' reduction.
Potential regional air quality impacts of cannabis cultivation facilities in Denver, Colorado
