Low-frequency variability and CO{sub 2} transient climate change. Part 3. Intermonthly and interannual variability
- National Center for Atmospheric Research, Boulder, CO (United States)
Components of interannual, intermonthly, and total monthly variability of lower troposphere temperature are calculated from a global coupled ocean-atmosphere general circulation model (GCM), from the same atmospheric model coupled to a nondynamic mixed-layer ocean, and from microwave sounding unit (MSU) satellite data. The coupled model produces most features of intermonthly and interannual variability, but with somewhat reduced amplitude in the extratropics and increased variability in the tropical western Pacific and tropical Atlantic. The short 14-year period of record of the MSU data precludes definitive conclusions about variability at longer time scales. Different 14-year periods from the coupled model show variability on those longer time scales that were noted in Part 1 of this series. The relative contributions of intermonthly and interannual variability making up total monthly variability are similar between coupled model and MSU data, suggesting that similar mechanisms are at work in both. Significant changes of variability noted in the coupled model with doubled carbon dioxide differ from the mixed-layer model and earlier studies. In the mixed-layer model intermonthly and interannual variability changes are similar with a mixture of increases and decreases, but with mainly decreases in the zonal mean from about 20{degree}S to 60{degree}N and near 60{degree}S. In the coupled model, intermonthly and interannual changes of variability with doubled CO{sub 2} show mostly increases of tropical interannual variability and decreases of intermonthly variability near 60{degree}N. These changes in the tropics are related to changes in ENSO and other regional hydrological regimes, while the alterations near 60{degree}N are likely associated with changes in blocking activity. These results point to the important contribution from ENSO seen in the coupled model and the MSU data that are not present in the mixed-layer model. 33 refs., 13 figs., 1 tab.
- OSTI ID:
- 443824
- Journal Information:
- Climate Dynamics, Vol. 10, Issue 6-7; Other Information: PBD: Sep 1994
- Country of Publication:
- United States
- Language:
- English
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