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Infrared Solar Spectroscopic Measurements of Free Tropospheric CO, C2H6, and HCN above Mauna Loa, Hawaii: Seasonal Variations and Evidence for Enhanced Emissions from the Southeast Asian Tropical Fires of 1997-1998High spectral resolution (0.003 per cm) infrared solar absorption measurements of CO, C2H6, and HCN have been recorded at the Network for the Detection of Stratospheric Change station on Mauna Loa, Hawaii, (19.5N, 155.6W, altitude 3.4 km). The observations were obtained on over 250 days between August 1995 and February 1998. Column measurements are reported for the 3.4-16 km altitude region, which corresponds approximately to the free troposphere above the station. Average CO mixing ratios computed for this layer have been compared with flask sampling CO measurements obtained in situ at the station during the same time period. Both show asymmetrical seasonal cycles superimposed on significant variability. The first 2 years of observations exhibit a broad January-April maximum and a sharper CO minimum during late summer. The C2H6 and CO 3.4-16 km columns were highly correlated throughout the observing period with the C2H6/CO slope intermediate between higher and lower values derived from similar infrared spectroscopic measurements at 32'N and 45'S latitude, respectively. Variable enhancements in CO, C2H6, and particularly HCN were observed beginning in about September 1997. The maximum HCN free tropospheric monthly mean column observed in November 1997 corresponds to an average 3.4-16 km mixing ratio of 0.7 ppbv (1 ppbv = 10(exp -9) per unit volume), more than a factor of 3 above the background level. The HCN enhancements continued through the end of the observational series. Back-trajectory calculations suggest that the emissions originated at low northern latitudes in southeast Asia. Surface CO mixing ratios and the C2H6 tropospheric columns measured during the same time also showed anomalous autumn 1997 maxima. The intense and widespread tropical wild fires that burned during the strong El Nino warm phase of 1997- 1998 are the likely source of the elevated emission products.
Document ID
19990115888
Acquisition Source
Langley Research Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Rinsland, C. P.
(NASA Langley Research Center Hampton, VA United States)
Goldman, A.
(Denver Univ. Denver, CO United States)
Murcray, F. J.
(Denver Univ. Denver, CO United States)
Stephen, T. M.
(Denver Univ. Denver, CO United States)
Pougatchev, N. S.
(Christopher Newport Univ. Newport News, VA United States)
Fishman, J.
(NASA Langley Research Center Hampton, VA United States)
David, S. J.
(Denver Univ. Denver, CO United States)
Blatherwick, R. D.
(Denver Univ. Denver, CO United States)
Novelli, P. C.
(National Oceanic and Atmospheric Administration Boulder, CO United States)
Jones, N. B.
(National Inst. of Water and Atmospheric Research Lauder, New Zealand)
Date Acquired
August 19, 2013
Publication Date
August 20, 1999
Publication Information
Publication: Journal of Geophysical Research
Publisher: American Geophysical Union
Volume: 104
Issue: D15
ISSN: 0148-0227
Subject Category
Environment Pollution
Report/Patent Number
Paper-1999JD900366
Funding Number(s)
CONTRACT_GRANT: NAG-351
CONTRACT_GRANT: CO-1221
Distribution Limits
Public
Copyright
Other

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