Af. Bouwman et Ja. Taylor, TESTING HIGH-RESOLUTION NITROUS-OXIDE EMISSION ESTIMATES AGAINST OBSERVATIONS USING AN ATMOSPHERIC TRANSPORT MODEL, Global biogeochemical cycles, 10(2), 1996, pp. 307-318
Global monthly estimates of N2O emissions were used to prescribe a thr
ee-dimensional atmospheric transport model. The simulated N2O surface
concentrations in the northern hemisphere (NH) are in general agreemen
t with atmospheric observations, about 1 ppb higher than in the southe
rn hemisphere (SH). The results suggest that N2O concentrations over s
trong source regions in continental interiors are much higher than tho
se over oceans. Simulated N2O concentrations in the MI, vary strongly
with the season, while the measured concentrations oscillate strongly
without seasonality. The modelled results for the SH show much less se
asonal variation, which is more consistent with atmospheric measuremen
t data. Most atmospheric N2O monitoring stations are not well situated
for verifying the simulated seasonality in atmospheric N2O. There is
only one continental site. In addition, atmospheric N2O observations f
rom different studies are sometimes contradictory. The difference betw
een model results and observations may be the result of local scale pu
lses of N2O acting on a much shorter timescale than the time step of 1
month of the emission inventory. Such N2O pulses may cause oscillatio
ns of the N2O concentration at the monitoring sites which dominate the
large-scale seasonality. It is also possible that source and sink pro
cesses other than those included in this study are operating. The tran
sport model does not include a description of the downward stratospher
e-troposphere flux of N2O which is greater in the NH than in the SH. T
he emission inventory does not account for soil N2O consumption in N-I
imited temperate ecosystems, and N2O emissions during autumn, thaw per
iods, and from snow covered soils. These potential errors and possible
underestimation of N2O emissions from combustion sources may exaggera
te the simulated seasonal trends.