Tendencies for changes in the phase characteristics of the annual cycle ofsurface air temperature for the Northern Hemisphere

Tendencies for changes in the phase characteristics of the annual cycle (AC ) of surface air temperature T-s for the Northern Hemisphere are analyzed o n the basis of observational data obtained over the past hundred years. The method of amplitude-phase characteristics is used in parallel with convent ional. Fourier analysis. The results obtained are compared to those obtaine d from an energy-balance model of climate, Under annual average warming, te ndencies are revealed for a general harmonization of the T-s AC to the sout h of the boundary of the snow-ice cover over Eurasia and for deharmonizatio n to the north of this boundary in the zones influenced by the winter Siber ian and Canadian anticyclones. These tendencies are due to the effect of th e planetary albedo-surface temperature feedback, Properties df the tendenci es for changes in the AC phase characteristics (which may also be associate d with cloudiness variations) are noted for the monsoon zone in southeaster n Eurasia and also in the zones influenced by the Atlantic storm tracks and in the desertification area in southwestern North America.