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Interannual and seasonal variability in atmospheric N 2 O
Author(s) -
Nevison Cynthia D.,
Mahowald Natalie M.,
Weiss Ray F.,
Prinn Ronald G.
Publication year - 2007
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2006gb002755
Subject(s) - environmental science , troposphere , atmospheric sciences , climatology , sink (geography) , sciamachy , zonal and meridional , atmospheric circulation , stratosphere , geology , geography , cartography
The increase in atmospheric N 2 O observed over the last century reflects large‐scale human perturbations to the global nitrogen cycle. High‐precision measurements of atmospheric N 2 O over the last decade reveal subtle signals of interannual variability (IAV) superimposed upon the more prominent growth trend. Anthropogenic sources drive the underlying growth in N 2 O, but are probably too monotonic to explain most of the observed IAV. The causes of both seasonal and interannual variability in atmospheric N 2 O are explored on the basis of comparisons of a 1993–2004 atmospheric transport simulation to observations of N 2 O at five stations of the Advanced Global Atmospheric Gases Experiment (AGAGE). The complementary tracers chlorofluorocarbons (CFCs) 11 and 12 and SF 6 also are examined. The model simulation does not include a stratospheric sink and thus isolates the effects of surface sources and tropospheric transport. Both model and observations yield correlations in seasonal and interannual variability among species, but only in a few cases are model and observed variability correlated to each other. The results suggest that tropospheric transport contributes substantially to observed variability, especially at Samoa station. However, some features of observed variability are not explained by the model simulation and appear more consistent with a stratospheric influence. At Mace Head, Ireland, N 2 O and CFC growth rate anomalies are weakly correlated to IAV in polar winter lower stratospheric temperature, a proxy for the strength of the mean meridional stratospheric circulation. Seasonal and interannual variability in the natural sources of N 2 O may also contribute to observed variability in atmospheric N 2 O.