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| Titel |
Observed and simulated short timescale variability of CO2 over Narita Airport |
| VerfasserIn |
Tomoko Shirai, Toshinobu Machida, Shamil Maksyutov, Hidekazu Matsueda, Yousuke Sawa, Yosuke Niwa, Kaz Higuchi |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250047864
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| Zusammenfassung |
| The synoptic scale variability of CO2 over the Narita International Airport (lat 35.8Ë N,
140.4Ë E, 43m a.s.l.) was investigated using measurements obtained from frequent
observation by commercial aircraft from November 2005 to March 2009, combined with
analyses of results from a transport model simulation for the year 2007. The synoptic
scale variability of CO2 mixing ratio, represented by the standard deviation (SD)
from fitted curves, increased at all altitudes during the summer, with a noticeable
increase in the upper troposphere in the spring. This seasonal/altitudinal change of SD
was statistically significant (within 1Ïă of inter-annual variability) throughout the
observation period and the model result agreed with the observation except the
underestimation of summertime SD. This discrepancy is probably caused by the combined
effect of underestimation of CO2 uptake by boreal vegetation and uncertainty in the
baiu (Japanese rainy season as part of the East Asian summer monsoon) climate
dynamics.
Tagged simulation was conducted to evaluate the relative contributions of regional
fluxes to the synoptic scale variability over Narita. The result indicated that the
major contribution was made by the fluxes in East Asia (mainly China) in the free
troposphere (FT) and by those in Japan in the planetary boundary layer (PBL),
respectively. Tagged simulation clearly showed enhanced transport of the CO2 flux from
East Asia to the upper troposphere over Narita in the spring, suggesting an active
passage of Asian outflow. The Asian outflow in the upper troposphere has been
investigated previously using reactive species like CO on a campaign to campaign basis.
This study is the first to clearly demonstrate the frequency of the Asian outflow in
the spring based on the observed high CO2 fluctuations detected in a multi-year
record.
We also conducted a model sensitivity analysis to evaluate the relative influence of
transport and flux variations on the CO2 SD over Narita for 2007. Changes in the surface flux
magnitude were found to affect the SD over Narita with height; 41% and 3% at 9km, 61%
and 4% at 5km, 19% and 83% at 0.5km when fluxes from East Asia and those
from Japan were doubled, respectively. This result indicated that SD over Narita is
sensitive to transport (synoptic scale meteorological variability) from upwind in
FT, but depends largely on the magnitude of local fluxes in the boundary layer. |
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