1950年平均经圈环流与角动量的平衡

MEAN MERIDIONAL CIRCULATION AND ANGULAR MOMENTUM BALANCE IN THE YEAR OF 1950

中文摘要:

      本文利用了Buch^[1]和Starr与White^[6]所计算的1950年各纬度上空的平均经向风速([v]),绘制了子午面上的平均环流(全年:图1,冬季:图2,夏季:图3),图中显示出三个环型(cell),低纬度和高纬度的两个正环型与中纬度的逆环型。1950年平均西风急流的位置正好处于中纬度的逆环流之中。全年平均的赤道辐合线位于北纬5°左右。自夏至冬三个环型均向北移,冬季半球Hadley环型伸向夏季半球去。三个环型的强度都是冬季大。对于1950年北半球10°—70°的角动量平衡也作了分析(图4),并绘制了这个空间中角动量输送流线图(图5),其中应该提出,就是通过东西风的界面流线是铅直的,也就是总的来说,在东风带里产生的角动量不是在水平方向上输送到西风带里去,而是在铅直方向上输送到低纬度的高空西风里去,再由那里在水平方向上送到中高纬度去。最后对于平均纬圈环流的维持也作了讨论,结论是:在中高纬度大型扰动起着主导作用,在低纬度则平均经圈环流是重要的。

英文摘要:

      Utiliziug the latitudinal mean of upper meridional wind of 1950 given by Buchrs^[5] and Stan and White^[6],mean meridional circulation has been studied.Fig.1-3 (fig.1 for whole year,fig.2 for winter,fig.3 for summer) reveal three cells:two direct cells in low and high latitudes respectively and one indirect cell in middle latitudes.The average jet straam of 1950 is situated in the middle cell.The yearly average equatorial convergence zone is at about 50°N.From winter to summer all the three cells shift northward.The Hadley cell of winter hemisphere extends to summer hemisphere.The intensity of these cells seems to be stronger in winter than in summer.Angular momentum balance for the latitudes 10°N-70°N for the year 1950 was also studied,and figure for stream lines for the transfer of angular momentum was constructed (fig.5).The most interesting feature in this figure is that through the surface separating easterlies and westerlies the stream lines are vertical.Thus it indicates that the angular momentum generated in the easterlies is transported to the westerlies not in horizontal direction,but transported to upper westerlies in low latity.ides by vertical motion.Then from there it is tzansfered to middle latitudes.The mechanism of such transfer is as follows:In Hadley cell the upward motion in equatorial region and southern tropics carries more angular momentum due to earth's rotation,while the downward motion in northern tropics and subtropics carries less angular momentarn due to earth's rotation.Thus in the mean angular momentum generated in easterlies is transported to upper levels.Finally the mechanism of maintenance of zonal circulation was discussed.conclusion is this:In middle arid high latitudes gross disturbances ate of primary importance while in low latitudes mean meridional cirulation is important in maintaining zonal circulation.