A NUMERICAL STUDY FOR MECHANISM OF THE EFFECT OF NORTHERN SUMMER ARCTIC ICE COVER ON THE GLOBAL SHORTRANGE CLIMATE CHANGE

In terms of nine-layer global spectral model involving fuller parameterization of physical process,with a rhomboidal truncation at wavenumber 15,experiments are conducted by virtue of two numerical schemes,one with long-range mean coverage of Arctic ice,and the other with supercooled water at the same temperature as the ice,followed by an analysis of the difference field simulated by the two schemes.Results show that(1)the impact of Arctic ice on the northern short-range climate is realized through the change in polar ice coverage to cause local temperature change in the polar region to set up gradient difference in temperature from north to south,thus affecting the atmospheric circulations and,on the other hand,two trains of two-dimensional Rossby waves excited by the atmospheric heat source anomaly have impacts on the Northern Hemisphere(NH)extratropical region,one of which is similar to the JP teleconnection pattern first presented by Nitta(1987);(2)The significant impact of Arctic ice anomaly on the southern short-range climate change is accomplished with the aid of the anomaly of the equatorial heat source that excites a two-dimensional Rossby wavetrain propagating along a great circle route into the Southern Hemisphere(SH)extratropics,and the cross-equatorial propagation of the NH wavetrain also has effects on the SH atmosphere.Simulation indicates that with the 15-day integration the Arctic ice exerts an influence mainly on the NH and when the model atmosphere is getting stabilized,the effect is dominantly on the SH short-range climate change.