摘要
本文利用1954—1956年的高空及地面记录,作出了平均流场,并计算了垂直速度、冷暖平流及辐射等,得出下面几点结论:1)冬季在1.5千米及3千米的西风,在高原西边有明显的分支,东边有明显的会合,且在东西两边各有一“死水区”(风速很小),在高原北面形成了高压脊,而在其南面形成了低槽,到了6千米除了二个“死水区”消失以外,其余基本上没有变化。2)夏季1.5千米及3千米在高原附近的流线,绕高原作气旋性旋转,而到了6千米则相反而呈反气旋性旋转,其中心在高原西南部分,且随高度增加而向西偏。3)夏季在高原上基本上是上升运动,可能达到9千米;冬季在高原上估计可能是下沉运动(除西南角有部分上升运动)。4)夏季可以肯定高原是一个热源,而冬季除了西南角有—部分是热源外,其他地区可能是一冷源。
First in this paper the mean 2-year mean winter and summer wind fields below 6km over Tibetan Plateau and its surrounding are presented.In winter the main features on 1.5km(fig.1)and 3 km(fig.2)level are the splitting of the westlies over the plateau,the line of convergence to the east of the plateau and the“dead-water”regions(characterized by calm wind and little disturbances,except small local vortices)respectively to the east and west of the plateau.On 6km(fig.4)the minor features disappear but the splitting is still evident.In summer in the vicinity of the plateau low level wind blows cyclonically around it(fig.6—7).Surround this large cyclonic whirl are small systems.On 6km(fig.8)the wind blows anticyclonically around the plateau.The center of the this anticyclone may be located at the SE corner of the plateau.This kind of vertical structure of this wind field indicates that the temperature over the plateau is higher than the surrounding.The region of high temperature is estimated to reach at least as high as 9 km.There is strong vertical motion in the vicinity of the plateau.In winter on its SE the motion is upward,while in the rest of the region the motion is in the main downward.In summer the mean motion fundamentally upward velocity reaches about 1 cm/sec,on 6km.Mean advection and temperature gradient(fig.5 for winter and fig.9 for summer)between 3—6km are also calculated from the wind data under geostrophic assumption.Secondly the heat balance over the plateau is estimated from the calculation of short wave absorption,codensation heating,long wave cooling,temperature advection,adiabatic cooling(or warming)due to vertical motion and turbulent heat transfer from the ground.From this calculation it is concluded that Tibetan Plateau is a heat source in summer,while in winter the result is not very conclusive.Probably in winter the SE part of it plays a role of warm source while the rest of the plateau plays a role of cold source.
作者
叶笃正
罗四维
朱抱真
YEH TU-CHENG;LO SZU-WEI;CHU PAO-CHEN(Institute of Meteorology and Geophysics)
出处
《气象学报》
1957年第2期108-121,共14页
Acta Meteorologica Sinica
