Early ship-based upper-air data and comparison with the Twentieth Century Reanalysis

Journal Article · 14 March 2011 · Climate of the Past (Online)

DOI: https://doi.org/10.5194/cp-7-265-2011 · OSTI ID:1564805

Brönnimann, S. ^[1]; Compo, G. P. ^[2]; Spadin, R. ^[3]; Allan, R. ^[4]; Adam, W. ^[5]

---

1. Federal Inst. of Technology, Zurich (Switzerland); Univ. of Bern (Switzerland)
2. Univ. of Colorado, Boulder, CO (United States); National Oceanic and Atmospheric Administration (NOAA), Boulder, CO (United States)
3. Federal Inst. of Technology, Zurich (Switzerland)
4. Atmospheric Circulation Reconstructions over the Earth (ACRE) (United Kingdom)
5. Lindenberg Meteorological Observatory (MOL) (Germany)

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.

• Research Organization: Univ. of California, Oakland, CA (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); Swiss National Science Foundation
• Grant/Contract Number: AC02-05CH11231; AC05-00OR22725
• OSTI ID: 1564805
• Journal Information: Climate of the Past (Online), Journal Name: Climate of the Past (Online) Journal Issue: 1 Vol. 7; ISSN 1814-9332
• Publisher: European Geophysical Union - CopernicusCopyright Statement
• Country of Publication: United States
• Language: English