On the Numerical Calculation of Eddy Flux

[摘要] Assuming that a small mass of air, which occupies a certain position, say x1, at time t, is diffused by eddy into its surrounding air within the limits of x1-s to x1+s at the next time t+τ, it was found that the eddy flux of any physical quantity per unit area for the time from t to t+τ can be calculated numerically by the formula (6), if the distribution of the quantity at time t is known.By the Simpson's 1/3 rule the formula (6) can be transformed into more convenient formula such as (71), (711), or (7111). Further these formulae can be also transformed into the formula (8), where A is the Austausch coefficient and _??_τ (x, t) the mean gradient of the distribution of the quantity for the time from t to t+τ. Fig. 3, I, II and III show how to determine the mean gradient from the curve of the distribution of the quantity, corresponding respectively to the formulae (71), (711), and (7111).In the case when τ is not small, it will be better to use the formula (13).In the tables 1 and 2 are compared the results of the theoretical and the numerical calculations for some exercises.

[学科分类] 大气科学