Premium
Observed NO/NO 2 Ratios in the Upper Troposphere Imply Errors in NO‐NO 2 ‐O 3 Cycling Kinetics or an Unaccounted NO x Reservoir
Author(s) -
Silvern R. F.,
Jacob D. J.,
Travis K. R.,
Sherwen T.,
Evans M. J.,
Cohen R. C.,
Laughner J. L.,
Hall S. R.,
Ullmann K.,
Crounse J. D.,
Wennberg P. O.,
Peischl J.,
Pollack I. B.
Publication year - 2018
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 - 10.1029/2018gl077728
Subject(s) - troposphere , jet propulsion , atmospheric sciences , environmental science , kinetic energy , reaction rate constant , photodissociation , meteorology , analytical chemistry (journal) , kinetics , chemistry , thermodynamics , environmental chemistry , physics , photochemistry , quantum mechanics
Observations from the SEAC 4 RS aircraft campaign over the southeast United States in August–September 2013 show NO/NO 2 concentration ratios in the upper troposphere that are approximately half of photochemical equilibrium values computed from Jet Propulsion Laboratory (JPL) kinetic data. One possible explanation is the presence of labile NO x reservoir species, presumably organic, decomposing thermally to NO 2 in the instrument. The NO 2 instrument corrects for this artifact from known labile HNO 4 and CH 3 O 2 NO 2 NO x reservoirs. To bridge the gap between measured and simulated NO 2 , additional unaccounted labile NO x reservoir species would have to be present at a mean concentration of ~40 ppt for the SEAC 4 RS conditions (compared with 197 ppt for NO x ). An alternative explanation is error in the low‐temperature rate constant for the NO + O 3 reaction (30% 1‐σ uncertainty in JPL at 240 K) and/or in the spectroscopic data for NO 2 photolysis (20% 1‐σ uncertainty). Resolving this discrepancy is important for understanding global budgets of tropospheric oxidants and for interpreting satellite observations of tropospheric NO 2 columns.