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Isoprene over the Amazon BasinData obtained during the 1985 ABLE expedition to the Amazon are used to describe the diurnal and vertical variations of isoprene. Isoprene is a natural hydrocarbon emitted by many species of trees, particularly those in tropical forests. The concentrations of isoprene at lower levels in the atmosphere undergo large diurnal variations, with the highest concentrations during midday and the lowest during the night. At ground level, outside the forest, peak concentrations of about 3-parts per billion by volume (ppbv) of isoprene were observed around midday. Concentrations were nearly zero before sunrise, increased to their maximum values during the day, and declined after sunset. Concentrations of 1-2 ppbv of isoprene were observed up to 300 m. Near the canopy level, up to 8 ppbv of isoprene were observed. In the forest, concentrations are generally quite low below the canopy and are highest at the level of the canopy. Since the reaction of isoprene with OH radicals is extremely fast, its concentrations fall off rapidly with altitude, so that practically none of it was seen above the boundary layer. During nighttime, however, concentrations comparable to daytime values were observed at altitudes of 300 m and above.
Document ID
19880040030
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Rasmussen, R. A.
(Oregon Graduate Center for Study and Research Beaverton, OR, United States)
Khalil, M. A. K.
(Oregon Graduate Center for Study and Research Beaverton, United States)
Date Acquired
August 13, 2013
Publication Date
February 20, 1988
Publication Information
Publication: Journal of Geophysical Research
Volume: 93
ISSN: 0148-0227
Subject Category
Geophysics
Accession Number
88A27257
Funding Number(s)
CONTRACT_GRANT: NAG1-589
Distribution Limits
Public
Copyright
Other

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