 |
| Titel |
First intercalibration of column-averaged methane from the Total Carbon Column Observing Network and the Network for the Detection of Atmospheric Composition Change |
| VerfasserIn |
R. Sussmann, A. Ostler, F. Forster, M. Rettinger, N. M. Deutscher, D. W. T. Griffith, J. W. Hannigan, N. Jones, P. K. Patra |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1867-1381
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 6, no. 2 ; Nr. 6, no. 2 (2013-02-20), S.397-418 |
| Datensatznummer |
250017398
|
| Publikation (Nr.) |
 copernicus.org/amt-6-397-2013.pdf |
|
|
|
|
|
| Zusammenfassung |
We present the first intercalibration of dry-air column-averaged mole
fractions of methane (XCH4) retrieved from solar Fourier transform
infrared (FTIR) measurements of the Network for the Detection of Atmospheric
Composition Change (NDACC) in the mid-infrared (MIR) versus near-infrared
(NIR) soundings from the Total Carbon Column Observing Network (TCCON). The
study uses multi-annual quasi-coincident MIR and NIR measurements from the
stations Garmisch, Germany (47.48° N, 11.06° E,
743 m a.s.l.), and Wollongong, Australia (34.41° S, 150.88° E,
30 m a.s.l.).
Direct comparison of the retrieved MIR and NIR XCH4 time series for
Garmisch shows a quasi-periodic seasonal bias leading to a standard
deviation (stdv) of the difference time series (NIR–MIR) of 7.2 ppb. After
reducing time-dependent a priori impact by using realistic site- and
time-dependent ACTM-simulated profiles as a common prior, the seasonal bias
is reduced (stdv = 5.2 ppb). A linear fit to the MIR/NIR scatter plot of
monthly means based on same-day coincidences does not show a y-intercept that
is statistically different from zero, and the MIR/NIR intercalibration
factor is found to be close to ideal within 2-σ uncertainty, i.e.
0.9996(8). The difference time series (NIR–MIR) do not show a significant
trend. The same basic findings hold for Wollongong. In particular an overall
MIR/NIR intercalibration factor close to the ideal 1 is found within 2-σ
uncertainty. At Wollongong the seasonal cycle of methane is less pronounced
and corresponding smoothing errors are not as significant, enabling standard
MIR and NIR retrievals to be used directly, without correction to a common a
priori.
Our results suggest that it is possible to set up a harmonized NDACC and
TCCON XCH4 data set which can be exploited for joint trend studies,
satellite validation, or the inverse modeling of sources and sinks. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|