Comparison of month-to-month persistence of anomalies in a general circulation model and in the Earth's atmosphere
Journal Article
·
· J. Atmos. Sci.; (United States)
The output of a 20-year integration of an annual cycle (AC) version of the NCAR Community Climate Model in which the external conditions went through 20 prescribed identical annual cycles is used to study month-to-month persistence of anomalies in monthly mean atmospheric circulation fields on a global and a hemispheric scale. Of all fields considered, the height fields (1000-300 mb) are the most persistent and the transient eddy flux fields the least persistent. Persistence in height field anomalies is largest in winter and small throughout the rest of the year. For the area north of 20/sup 0/N, a comparison is made with the persistence of monthly mean height and temperature fields observed in the real world (RW) during a 28-year interval. On a pooled all month-pairs basis, RW height anomaly fields are significantly more persistent than those appearing in AC but, from a practical point of view, the difference is small. The differences in persistence are larger for temperature anomalies (500-1000 mb thickness) than for height. Differences between RW and AC monthly persistence over the area north of 20/sup 0/N are largest in summer when the RW has a local maximum in persistence. On the assumption that the model and atmosphere have the same internal dynamics, the differences just described can be attributed to the interaction of the atmosphere with external or boundary conditions (e.g., ocean surface temperatures), which was purposely omitted from the AC integration. Interaction with the lower boundary in summer seems, therefore, to be quite important to explain the observed level of month-to-month persistence in circulation anomalies. In winter, however, the internal dynamics of the atmosphere alone produces the required observed level of month-to-month persistence. 20 references, 6 figures, 7 tables.
- Research Organization:
- Univ. of Maryland, College Park
- OSTI ID:
- 6944425
- Journal Information:
- J. Atmos. Sci.; (United States), Journal Name: J. Atmos. Sci.; (United States) Vol. 43:14; ISSN JAHSA
- Country of Publication:
- United States
- Language:
- English
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