 |
| Titel |
Does GOSAT capture the true seasonal cycle of carbon dioxide? |
| VerfasserIn |
H. Lindqvist, C. W. O'Dell, S. Basu, H. Boesch, F. Chevallier, N. Deutscher, L. Feng, B. Fisher, F. Hase, M. Inoue, R. Kivi, I. Morino, P. I. Palmer, R. Parker, M. Schneider, R. Sussmann, Y. Yoshida |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 22 ; Nr. 15, no. 22 (2015-11-24), S.13023-13040 |
| Datensatznummer |
250120181
|
| Publikation (Nr.) |
 copernicus.org/acp-15-13023-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
| The seasonal cycle accounts for a dominant mode of total column CO2
(XCO2) annual variability and is connected to CO2 uptake and release;
it thus represents an important quantity to test the accuracy of the
measurements from space. We quantitatively evaluate the XCO2 seasonal
cycle of the Greenhouse Gases Observing Satellite (GOSAT) observations from
the Atmospheric CO2 Observations from Space (ACOS) retrieval system
and compare average regional seasonal cycle features to those directly
measured by the Total Carbon Column Observing Network (TCCON). We analyse the
mean seasonal cycle amplitude, dates of maximum and minimum XCO2, as well
as the regional growth rates in XCO2 through the fitted trend over several
years. We find that GOSAT/ACOS captures the seasonal cycle amplitude within
1.0 ppm accuracy compared to TCCON, except in Europe, where the difference
exceeds 1.0 ppm at two sites, and the amplitude captured by GOSAT/ACOS is
generally shallower compared to TCCON. This bias over Europe is not as large
for the other GOSAT retrieval algorithms (NIES v02.21, RemoTeC v2.35, UoL
v5.1, and NIES PPDF-S v.02.11), although they have significant biases at
other sites. We find that the ACOS bias correction partially explains the
shallow amplitude over Europe. The impact of the co-location method and
aerosol changes in the ACOS algorithm were also tested and found to be few
tenths of a ppm and mostly non-systematic. We find generally good agreement
in the date of minimum XCO2 between ACOS and TCCON, but ACOS generally
infers a date of maximum XCO2 2–3 weeks later than TCCON. We further
analyse the latitudinal dependence of the seasonal cycle amplitude throughout
the Northern Hemisphere and compare the dependence to that predicted by
current optimized models that assimilate in situ measurements of CO2. In
the zonal averages, models are consistent with the GOSAT amplitude to within
1.4 ppm, depending on the model and latitude. We also show that the seasonal
cycle of XCO2 depends on longitude especially at the mid-latitudes: the
amplitude of GOSAT XCO2 doubles from western USA to East Asia at
45–50° N, which is only partially shown by the models. In general,
we find that model-to-model differences can be larger than GOSAT-to-model
differences. These results suggest that GOSAT/ACOS retrievals of the XCO2
seasonal cycle may be sufficiently accurate to evaluate land surface models
in regions with significant discrepancies between the models. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|