Ozone seasonal evolution and photochemical production regime in the polluted troposphere in eastern China derived from high-resolution Fourier transform spectrometry (FTS) observations
2018
Abstract. The seasonal evolution of O 3 and its photochemical
production regime in a polluted region of eastern China between 2014 and 2017
has been investigated using observations. We used tropospheric ozone
( O 3 ), carbon monoxide (CO), and formaldehyde (HCHO, a marker of VOCs
(volatile organic compounds)) partial columns derived from high-resolution
Fourier transform spectrometry (FTS); tropospheric nitrogen dioxide
( NO 2 , a marker of NO x (nitrogen oxides)) partial
column deduced from the Ozone Monitoring Instrument (OMI); surface meteorological
data; and a back trajectory cluster analysis technique. A broad O 3
maximum during both spring and summer (MAM/JJA) is observed; the day-to-day
variations in MAM/JJA are generally larger than those in autumn and winter
(SON/DJF). Tropospheric O 3 columns in June are 1.55×10 18 molecules cm −2 (56 DU (Dobson units)), and in December they are
1.05×10 18 molecules cm −2 (39 DU). Tropospheric O 3
columns in June were ∼50 % higher than those in December. Compared
with the SON/DJF season, the observed tropospheric O 3 levels in MAM/JJA
are more influenced by the transport of air masses from densely populated and
industrialized areas, and the high O 3 level and variability in
MAM/JJA is determined by the photochemical O 3 production. The
tropospheric-column HCHO∕NO 2 ratio is used as a proxy to
investigate the photochemical O 3 production rate ( PO 3 ).
The results show that the PO 3 is mainly nitrogen oxide ( NO x ) limited in MAM/JJA, while it is mainly VOC or mixed VOC– NO x limited in SON/DJF. Statistics show that
NO x -limited, mixed VOC– NO x -limited, and VOC-limited PO 3 accounts for 60.1 %, 28.7 %, and 11 % of days,
respectively. Considering most of PO 3 is NO x
limited or mixed VOC– NO x limited, reductions in
NO x would reduce O 3 pollution in eastern China.
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