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(一) 現时制作1000mb面預报图的方法(指图解法数值預报,下同)都是間接法,卽必須先計算其他变量的变化,而后方能計算1000mb面的变高。大多数方法是先計算500mb面的变高,如Estoque(1956,1957a,1957b),Reed(1957,1958),以及作者提出的“第二法”(1958b);亦有先計算500/1000mb厚度变化者,如作者所提出的“第一法”(1958a)。这种間接法的缺点有二:(1)制作1000mb預报图的手續及时間均因此大为增加。(2)制作预报图的误差是累积的,在間接法里制作其他变量預报图的誤差,最后必然使制作1000mb面预报图的誤差有不必要的增加,有时可能很大。如Reed(1957)
(A) At present, the method for producing a 1000-m forecast map (numerical forecasting of the graphic method is the same as the following) is an indirect method. Therefore, the change of other variables must be calculated first and then the height of the 1000-mb plane can be calculated. Most of the methods are to calculate the height of the 500mb surface first, such as Estoque (1956, 1957a, 1957b), Reed (1957, 1958) and the author’s “second method” (1958b) Changes, such as the author’s “First Law” (1958a). The disadvantages of this indirect method are twofold: (1) The procedure and time for making a 1000-m forecast map are greatly increased. (2) The errors in making the forecast map are cumulative. Making the error in the forecast map of other variables in the indirect method inevitably makes the error in making the 1000-m forecast map unnecessarily increase, which may sometimes be large. As Reed (1957)