THE RELATIONSHIP BETWEEN THE INTERANNUAL VARIABILITY OF AIR TEMPERATURE OVER THE TIBETAN PLATEAU AND THE NORTHERN HEMISPHERIC ANNULAR-WAVE PATTERN

By using 64 stationbased surface air temperature over the mideastern Tibetan Plateau and the ERA40 Reanalysis data in the period Jan 1961－Feb 2002, the anomalous largescale circulation pattern related to the interannual variability of air temperature over the Tibetan Plateau has been investigated. Results show that, except in summer, there is a significant positive correlation between the surface air temperature over the plateau and the Northern Hemispheric subtropical and polar tropospheric air temperature and geopotential height fields. Among the subtropical annular belt, five correlation centers exist over the Tibetan Plateau, west Pacific, northern North America, mid Atlantic, as well as the area from north Africa to Arabia. However, an inversed negative correlation belt can be detected in the mid-high latitudes. Therefore, these three annular activity belts together with the five subtropical activity centers form a kind of Northern Hemispheric annular-wave mode. In zonal direction, it is characterized by abnormally strong tropospheric westerlies in mid-latitudes and easterlies in tropical and high latitudes, which is accompanied by the weakened long wave troughs and ridges over mid-latitudes. In meridional direction, it is characterized by abnormally strong Hadley and Ferrel cells, which is accompanied by intensified subtropical descent and mid-latitudes ascent. And this annular-wave mode is also featured by the equivalentbarotropic structure in vertical. When this annularwave mode in its positive phase, the integrated effect of the weakened cold air intrusion and enhanced adiabatic descent leads to the anomalous warm in the mid and lower troposphere over the plateau.