| タイトル | Tropospheric Ozone Increases over the Southern Africa Region: Bellwether for Rapid Growth in Southern Hemisphere Pollution? |
| 著者（英） | Posny, F.; Thompson, Anne M.; Thouret, V.; Coetzee, J. G. R.; Witte, J. C.; Balashov, Nikolay V. |
| 著者所属（英） | NASA Goddard Space Flight Center |
| 発行日 | 2014-09-17 |
| 言語 | eng |
| 内容記述 | Increases in free-tropospheric (FT) ozone based on ozonesonde records from the early 1990s through 2008 over two subtropical stations, Irene (near Pretoria, South Africa) and Runion (21 deg. S, 55 deg. E; approx. 2800 km NE of Irene in the Indian Ocean), have been reported. Over Irene a large increase in the urban-influenced boundary layer (BL, 1.5-4 km) was also observed during the 18-year period, equivalent to 30%decade1. Here we show that the Irene BL trend is at least partly due to a gradual change in the sonde launch times from early morning to the midday period. The FT ozone profiles over Irene in 1990-2007 are re-examined, filling in a 1995-1999 gap with ozone profiles taken during the Measurements of Ozone by Airbus In-service Aircraft (MOZAIC) project over nearby Johannesburg. A multivariate regression model that accounts for the annual ozone cycle, El Nio-Southern Oscillation (ENSO) and possible tropopause changes was applied to monthly averaged Irene data from 4 to 11 km and to 1992-2011 Runion sonde data from 4 to 15 km. Statistically significant trends appear predominantly in the middle and upper troposphere (UT; 4-11 km over Irene, 4-15 km over Runion) in winter (June-August), with increases 1 ppbv yr(exp. 1) over Irene and approx. 2 ppbv yr(exp. 1) over Runion. These changes are equivalent to approx. 25 and 35-45%decade( exp. 1), respectively. Both stations also display smaller positive trends in summer, with a 45%decade(exp. 1) ozone increase near the tropopause over Runion in December. To explain the ozone increases, we investigated a time series of dynamical markers, e.g., potential vorticity (PV) at 330-350 K. PV affects UT ozone over Irene in November-December but displays little relationship with ozone over Runion. A more likely reason for wintertime FT ozone increases over Irene and Runion appears to be long-range transport of growing pollution in the Southern Hemisphere. The ozone increases are consistent with trajectory origins of air parcels sampled by the sondes and with recent NOx emissions trends estimated for Africa, South America and Madagascar. For Runion trajectories also point to sources from the eastern Indian Ocean and Asia. |
| NASA分類 | Meteorology and Climatology; Environment Pollution |
| レポートNO | GSFC-E-DAA-TN31806 |
| 権利 | Copyright |
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