Light Hydrocarbons in the Tropospheric Boundary Layer over Tropical Africa
We present C2–C6 nonmethane hydrocarbon (NMHC) measurements from canister samples obtained in the extratropical lower stratosphere during the fall (November/December 1995), winter (March 1997), and summer seasons (July 1998) as part of the stratosphere-troposphere experiments by aircraft measurement...
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ftyorkuniv:oai:yorkspace.library.yorku.ca:10315/4103 2023-10-01T03:57:11+02:00 Light Hydrocarbons in the Tropospheric Boundary Layer over Tropical Africa Rudolph, J. Khedim, A. Bonsang, B. 1992 application/pdf http://hdl.handle.net/10315/4103 en eng AGU J. Geophys. Res., 97, 6181-6186 http://hdl.handle.net/10315/4103 http://www.agu.org/journals/jd/ airborne measurements chemical composition cross-tropopause transport Article 1992 ftyorkuniv 2023-09-02T23:02:31Z We present C2–C6 nonmethane hydrocarbon (NMHC) measurements from canister samples obtained in the extratropical lower stratosphere during the fall (November/December 1995), winter (March 1997), and summer seasons (July 1998) as part of the stratosphere-troposphere experiments by aircraft measurements campaign. The flights were carried out from Amsterdam (Netherlands, 52°N, 4.5°E) during fall, from Kiruna (Sweden, 68°N, 20°E) during winter, and from Timmins (Canada, 48.2°N, 70.3°W) during summer. The NMHC measurements have been evaluated along with concurrent in situ measurements of acetone (CH3COCH3), CO, O3, N2O, and CFC-12 (CCl2F2). The vertical distributions of NMHC and acetone as a function of O3 and potential temperature in the lowermost stratosphere show a strong seasonality. Enhanced concentrations of NMHC + CH3COCH3 were found during July up to potential temperatures of Θ = 370 K, whereas during March this was limited to Θ = 340 K, in agreement with stronger isentropic cross-tropopause transport during summer. Increasing methyl chloride (CH3Cl) concentrations with altitude were measured during July, pointing to mixing at the subtropical tropopause. During summer and fall, mean NMHC + acetone concentrations were more than a factor of 2 higher than that during winter. Box model calculations indicate that the observed acetone levels of 0.5–1 ppbv can explain 30–50% of the enhanced OH radical concentrations in the summertime lowermost stratosphere. Using mass balance calculations, we show that a significant tropospheric fraction (≤30%) was present up to Θ = 370 K in the summertime lowermost stratosphere. During winter, the tropospheric fraction approached zero at about Θ = 350 K. The time between selected troposphere-to-stratosphere mixing events and the aircraft measurements has been estimated at 3–14 days. Our results emphasize that isentropic cross-tropopause transport can be a fast process occurring on timescales of days to weeks. Article in Journal/Newspaper Kiruna York University, Toronto: YorkSpace Kiruna Canada |
institution |
Open Polar |
collection |
York University, Toronto: YorkSpace |
op_collection_id |
ftyorkuniv |
language |
English |
topic |
airborne measurements chemical composition cross-tropopause transport |
spellingShingle |
airborne measurements chemical composition cross-tropopause transport Rudolph, J. Khedim, A. Bonsang, B. Light Hydrocarbons in the Tropospheric Boundary Layer over Tropical Africa |
topic_facet |
airborne measurements chemical composition cross-tropopause transport |
description |
We present C2–C6 nonmethane hydrocarbon (NMHC) measurements from canister samples obtained in the extratropical lower stratosphere during the fall (November/December 1995), winter (March 1997), and summer seasons (July 1998) as part of the stratosphere-troposphere experiments by aircraft measurements campaign. The flights were carried out from Amsterdam (Netherlands, 52°N, 4.5°E) during fall, from Kiruna (Sweden, 68°N, 20°E) during winter, and from Timmins (Canada, 48.2°N, 70.3°W) during summer. The NMHC measurements have been evaluated along with concurrent in situ measurements of acetone (CH3COCH3), CO, O3, N2O, and CFC-12 (CCl2F2). The vertical distributions of NMHC and acetone as a function of O3 and potential temperature in the lowermost stratosphere show a strong seasonality. Enhanced concentrations of NMHC + CH3COCH3 were found during July up to potential temperatures of Θ = 370 K, whereas during March this was limited to Θ = 340 K, in agreement with stronger isentropic cross-tropopause transport during summer. Increasing methyl chloride (CH3Cl) concentrations with altitude were measured during July, pointing to mixing at the subtropical tropopause. During summer and fall, mean NMHC + acetone concentrations were more than a factor of 2 higher than that during winter. Box model calculations indicate that the observed acetone levels of 0.5–1 ppbv can explain 30–50% of the enhanced OH radical concentrations in the summertime lowermost stratosphere. Using mass balance calculations, we show that a significant tropospheric fraction (≤30%) was present up to Θ = 370 K in the summertime lowermost stratosphere. During winter, the tropospheric fraction approached zero at about Θ = 350 K. The time between selected troposphere-to-stratosphere mixing events and the aircraft measurements has been estimated at 3–14 days. Our results emphasize that isentropic cross-tropopause transport can be a fast process occurring on timescales of days to weeks. |
format |
Article in Journal/Newspaper |
author |
Rudolph, J. Khedim, A. Bonsang, B. |
author_facet |
Rudolph, J. Khedim, A. Bonsang, B. |
author_sort |
Rudolph, J. |
title |
Light Hydrocarbons in the Tropospheric Boundary Layer over Tropical Africa |
title_short |
Light Hydrocarbons in the Tropospheric Boundary Layer over Tropical Africa |
title_full |
Light Hydrocarbons in the Tropospheric Boundary Layer over Tropical Africa |
title_fullStr |
Light Hydrocarbons in the Tropospheric Boundary Layer over Tropical Africa |
title_full_unstemmed |
Light Hydrocarbons in the Tropospheric Boundary Layer over Tropical Africa |
title_sort |
light hydrocarbons in the tropospheric boundary layer over tropical africa |
publisher |
AGU |
publishDate |
1992 |
url |
http://hdl.handle.net/10315/4103 |
geographic |
Kiruna Canada |
geographic_facet |
Kiruna Canada |
genre |
Kiruna |
genre_facet |
Kiruna |
op_relation |
J. Geophys. Res., 97, 6181-6186 http://hdl.handle.net/10315/4103 |
op_rights |
http://www.agu.org/journals/jd/ |
_version_ |
1778528233488121856 |