Open AccessNO x and NO y over the northwestern North Atlantic: Measurements and measurement accuracy
Author(s) -
Peterson Matthew C.,
Honrath Richard E.
Publication year - 1999
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/1998jd100088
Subject(s) - environmental science , climatology , reactive nitrogen , atmospheric sciences , magnitude (astronomy) , gulf stream , oceanography , nitrogen , geology , physics , quantum mechanics , astronomy
Measurements of NO x (NO+NO 2 ) and NO y (total reactive nitrogen oxides) during February‐April 1996 at the northern tip of Newfoundland are used to determine levels in the local marine boundary layer (MBL) and assess the adequacy of current understanding of the processes controlling NO x levels over the northern North Atlantic, as expressed through previously reported simulations using the Geophysical Fluid Dynamics Laboratory (GFDL) Global Chemical Transport Model (GCTM). Median mixing ratios of NO x and NO y in the local MBL were 24 parts per trillion by volume (pptv) and 200 pptv, respectively. These levels are 35–64% above background levels measured in the remote MBL in summer and fall during the Chemical Instrumentation Test and Evaluation (CITE 2), North Atlantic Regional Experiment (NARE‐93), and Pacific Exploratory Mission‐West (PEM‐West) A measurement campaigns and are similar to or somewhat higher than anthropogenically influenced levels observed in winter‐spring during the PEM‐West B campaign. The magnitude of median NO x and NO y , levels in the local MBL is not due to events with high reactive nitrogen oxides levels. Instead, these relatively high median levels are likely the result of dispersion of anthropogenic emissions over a large region. A detailed comparison with results from the GFDL GCTM indicates that measured March and April average NO x levels are significantly lower than simulated levels over the north central North Atlantic. The frequency and magnitude of modeled and observed elevated‐NO x events were similar, indicating that the conditions responsible for relatively direct long‐range transport events were similar. This indicates that interannual variability probably did not cause the discrepancy in monthly average NO x values. However, simulated elevated NO x events are much longer than are observed. This difference appears to be at least partially responsible for the higher average NO x values simulated by the model. These results indicate that model‐based estimates of this region's contributions to the global ozone budget may be too high. Accuracy of the NO x measurements is estimated to be 6%, while conservative analysis of conversion efficiencies indicates a negative bias of ≲18% in the determination of gas‐phase NO y compounds.