Positive and negative influences of typhoons on tropospheric ozone over southern China
<p>Based on an ensemble of 17 typhoons that made landfall between 2014 and 2018, we investigate the positive and negative influences of typhoons on tropospheric ozone over southern China. With respect to the proximity of typhoon centres and the typhoon developmental stages, we find that surfac...
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| Autores principales: | , , , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
Copernicus Publications
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/0320e6acd21b4fc99c70fc7739219b70 |
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| Sumario: | <p>Based on an ensemble of 17 typhoons that made landfall between
2014 and 2018, we investigate the positive and negative influences of typhoons on
tropospheric ozone over southern China. With respect to the
proximity of typhoon centres and the typhoon developmental stages, we find that
surface ozone is enhanced when typhoons are 400–1500 km away during the
initial stages of development (e.g. from 1 d before to 1 d after
typhoon genesis). The positive ozone anomalies reach 10–20 ppbv
above the background ozone level on average. The maximum enhancement of surface ozone
appears at a radial distance of 1100–1300 km from the typhoon centre during
these initial stages. As the typhoons approach southern China, the
influences of these systems switch to reducing ozone and, hence, lead to negative
ozone anomalies of 6–9 ppbv. Exploring the linkages between ozone
variations and typhoon-induced meteorological evolution, we find that increasing temperature and weak winds in
the atmospheric boundary layer (ABL) and dominating downward motions promote
ozone production and accumulation over the outskirts of typhoons during typhoon initial stages, whereas
deteriorating weather, accompanied by dropping temperature, wind gales and
convective activity, reduces the production and accumulation of surface ozone
when typhoons are making landfall.</p>
<p>We further examine the impacts of typhoons on tropospheric ozone
profiles vertically, especially the influences of typhoon-induced
stratospheric intrusions on lower troposphere and surface ozone. Based on
temporally dense ozone profile observations, we find two high-ozone regions,
located in the ABL and the middle to upper troposphere respectively, during
different typhoon stages. On average, the high-ozone region in the ABL has a maximum
ozone enhancement of 10–12 ppbv at 1–1.5 km altitude during the initial typhoon
stages. In the high-ozone region in the middle to upper troposphere, ozone enhancement
persists over a longer period with a maximum ozone enhancement of
<span class="inline-formula">∼</span> 10 ppbv at 7–8 km altitude shortly after typhoon genesis; this value
increases to <span class="inline-formula">∼</span> 30 ppbv near 12 km altitude when typhoons reach their
maximum intensity. When typhoons make landfall, negative ozone anomalies
appear and extend upward with a maximum ozone reduction of 14–18 ppbv at 5 km altitude and 20–25 ppbv at 11 km altitude. Although the overall
tropospheric ozone is usually reduced during typhoon landfall, we find
that five of eight typhoon samples induced ozone-rich air with a
stratospheric origin above 4 km altitude; moreover, in three typhoon cases, the
ozone-rich air intrusions can sink to the ABL. This suggests that the
typhoon-induced stratospheric intrusions play an important role in surface
ozone enhancement.</p> |
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