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| Titel |
Early ship-based upper-air data and comparison with the Twentieth Century Reanalysis |
| VerfasserIn |
S. Brönnimann, G. P. Compo, R. Spadin, R. Allan, W. Adam |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 7, no. 1 ; Nr. 7, no. 1 (2011-03-14), S.265-276 |
| Datensatznummer |
250004410
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| Publikation (Nr.) |
 copernicus.org/cp-7-265-2011.pdf |
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| Zusammenfassung |
| Extension of 3-D atmospheric data products back into the past is desirable
for a wide range of applications. Historical upper-air data are important in
this endeavour, particularly in the maritime regions of the tropics and the
southern hemisphere, where observations are extremely sparse. Here we present
newly digitized and re-evaluated early ship-based upper-air data from two
cruises: (1) kite and registering balloon profiles from onboard the ship SMS
Planet on a cruise from Europe around South Africa and across the
Indian Ocean to the western Pacific in 1906/1907, and (2) ship-based
radiosonde data from onboard the MS Schwabenland on a cruise from
Europe across the Atlantic to Antarctica and back in 1938/1939. We describe
the data and provide estimations of the errors. We compare the data with a
recent reanalysis (the Twentieth Century Reanalysis Project, 20CR, Compo et
al., 2011) that provides global 3-D data back to the 19th century based on an
assimilation of surface pressure data only (plus monthly mean sea-surface
temperatures). In cruise (1), the agreement is generally good, but large
temperature differences appear during a period with a strong inversion. In
cruise (2), after a subset of the data are corrected, close agreement between observations and 20CR is
found for geopotential height (GPH) and temperature notwithstanding a likely cold bias of 20CR at the tropopause level.
Results are considerably worse for relative humidity, which was reportedly
inaccurately measured. Note that comparing 20CR, which has limited skill in the tropical
regions, with measurements from ships in remote regions made under sometimes
difficult conditions can be considered a worst case assessment. In view of that fact, the anomaly correlations for
temperature of 0.3–0.6 in the lower troposphere in cruise (1) and of
0.5–0.7 for tropospheric temperature and GPH in cruise (2) are considered as
promising results. Moreover, they are consistent with the error estimations.
The results suggest room for further improvement of data products in remote regions. |
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