Lagrangian analysis of low level anthropogenic plume processing across the North Atlantic
International audience The photochemical evolution of an anthropogenic plume from the New-York/Boston region during its transport at low altitudes over the North Atlantic to the European west coast has been studied using a Lagrangian framework. This plume, originally strongly polluted, was sampled b...
Main Authors: | , , , , , , , , , , , , , , |
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Other Authors: | , , , , , , , , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
HAL CCSD
2008
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Subjects: | |
Online Access: | https://hal.science/hal-00328323 https://hal.science/hal-00328323/document https://hal.science/hal-00328323/file/acpd-8-7509-2008.pdf https://doi.org/10.5194/acpd-8-7509-2008 |
Summary: | International audience The photochemical evolution of an anthropogenic plume from the New-York/Boston region during its transport at low altitudes over the North Atlantic to the European west coast has been studied using a Lagrangian framework. This plume, originally strongly polluted, was sampled by research aircraft just off the North American east coast on 3 successive days, and 3 days downwind off the west coast of Ireland where another aircraft re-sampled a weakly polluted plume. Changes in trace gas concentrations during transport were reproduced using a photochemical trajectory model including deposition and mixing effects. Chemical and wet deposition processing dominated the evolution of all pollutants in the plume. The mean net O 3 production was evaluated to be -5 ppbv/day leading to low values of O 3 by the time the plume reached Europe. Wet deposition of nitric acid was responsible for an 80% reduction in this O 3 production. If the plume had not encountered precipitation, it would have reached the Europe with O 3 levels up to 80-90 ppbv, and CO levels between 120 and 140 ppbv. Photochemical destruction also played a more important role than mixing in the evolution of plume CO due to high levels of both O 3 and water vapour showing that CO cannot always be used as a tracer for polluted air masses, especially for plumes transported at low altitudes. The results also show that, in this case, an important increase in the O 3 /CO slope can be attributed to chemical destruction of CO and not to photochemical O 3 production as is often assumed. |
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