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In situ measurements of the NO 2 /NO ratio for testing atmospheric photochemical models
Author(s) -
Jaeglé L.,
Webster C. R.,
May R. D.,
Fahey D. W.,
Woodbridge E. L.,
Keim E. R.,
Gao R. S.,
Proffitt M. H.,
Stimpfle R. M.,
Salawitch R. J.,
Wofsy S. C.,
Pfister L.
Publication year - 1994
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/94gl02717
Subject(s) - stratosphere , daytime , atmospheric sciences , environmental science , atmospheric chemistry , photodissociation , latitude , ozone , steady state (chemistry) , nox , standard deviation , aerosol , meteorology , mixing ratio , range (aeronautics) , chemistry , materials science , photochemistry , physics , combustion , geology , geodesy , mathematics , statistics , composite material , organic chemistry
Simultaneous in situ measurements of NO 2 , NO, O 3 , ClO, pressure and temperature have been made for the first time, presenting a unique opportunity to test our current understanding of the photochemistry of the lower stratosphere. Data were collected from several flights of the ER‐2 aircraft at mid‐latitudes in May 1993 during NASA's Stratospheric Photochemistry, Aerosols and Dynamics Expedition (SPADE). The daytime ratio of NO 2 /NO remains fairly constant at 19 km with a typical value of 0.68 and standard deviation of ± 0.17. The ratio observations are compared with simple steady‐state calculations based on laboratory‐measured reaction rates and modeled NO 2 photolysis rates. At each measurement point the daytime NO 2 /NO with its measurement uncertainty overlap the results of steady‐state calculations and associated uncertainty. However, over all the ER‐2 flights examined, the model systematically overestimates the ratio by 40% on average. Possible sources of error are examined in both model and measurements. It is shown that more accurate laboratory determinations of the NO + O 3 reaction rate and of the NO 2 cross‐sections in the 200–220 K temperature range characteristic of the lower stratosphere would allow for a more robust test of our knowledge of NOx photochemistry by reducing significant sources of uncertainties in the interpretation of stratospheric measurements. The present measurements are compared with earlier observations of the ratio at higher altitudes.