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991.
Aspects of the intraseasonal oscillation simulated by the Hadley Centre Atmosphere Model 总被引：2，自引：0，他引：2
The period and amplitude of the tropical intraseasonal oscillation in the Hadley Centre Global Climate Model have been examined
by applying time filtering and spectral analysis techniques to time series of daily velocity potential. Results from an AMIP
integration of the model, forced with observed sea surface temperatures for the decade 1979-88 show that the model has a reasonable
degree of skill in simulating the main features of the oscillation, although the signal in the model is rather noisy compared
to NWP analyses. The model also shows interannual variability of the oscillation similar in magnitude to that in the analyses.
The impact on the oscillation of including a parametrization of momentum transport by cumulus convection is assessed. This
parametrization significantly improves the mean circulation of the model, reducing systematic errors particularly in the tropics.
However, the strength and coherence of the tropical intraseasonal oscillation are significantly reduced by this parametrization.
It is speculated that this may be related to a reduction in westerly flow in the tropical central and east Pacific and a reduction
in the strength of the SPCZ in DJF.
Received: 17 July 1996/Accepted: 30 January 1997 相似文献
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An increase in global average precipitation of about 10% is simulated by two global climate models with mixed layer oceans
in response to an equilibrium doubling of carbon dioxide. The UKHI model was developed in the United Kingdom at the Hadley
Centre for Climate Prediction and Research and the CSIRO9 model was developed in Australia by the CSIRO Division of Atmospheric
Research. Regional changes in daily precipitation simulated by these models have been compared. Both models simulate fewer
wet days in middle latitudes, and more wet days in high latitudes. At middle and low latitudes, there is a shift in the precipitation
type toward more intense convective events, and fewer moderate non-convective events. At high latitudes, the precipitation
type remains non-convective and all events simply get heavier, resulting in fewer light events and more moderate and heavy
events. The probability of heavy daily precipitation increases by more than 50% in many locations. Extreme events with a probability
of 1% or less were considered in terms of return periods (the average period between events of the same magnitude). For a
given return period of at least 1 y, precipitation intensity in Europe, USA, Australia and India increases by 10 to 25%. For
a given precipitation intensity, the average return period becomes shorter by a factor of 2 to 5. Given that larger changes
in frequency occur for heavier simulated events, changes may be even greater for more-extreme events not resolved by models.
Received: 1 July 1996 / Accepted: 21 March 1997 相似文献
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The Hudson Bay common eider ( Somateria molissima sedentaria ) is a unique subspecies of eider that remains within the confines of Hudson Bay throughout the year. We compared clutch, egg and body size variation among populations of common eiders breeding in eastern and western Hudson Bay. Clutch size did not differ substantially among these populations. All eiders in Hudson Bay laid larger clutches than other subspecies in eastern North America. As Hudson Bay common eiders do not undergo extensive migrations, they may have more energy reserves available to them for egg production. Eiders nesting in eastern Hudson Bay laid larger eggs than eiders nesting in western Hudson Bay. Further, eiders in eastern Hudson Bay tended to be structurally larger, but had smaller bill processes. These differences may have a genetic basis. Smaller egg size and body size may arise in western Hudson Bay from mixing with the smaller borealis subspecies nesting to the north. Further work to resolve genetic affinities, determine levels of male and female dispersal, and examine variation in reproductive ecology are needed to resolve the sources of these differences. 相似文献
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