Study of the Symmetry Charactars Found on the Pressure Curve and Application of its resulte to Long-Rang Forecasting

[摘要] It has been often observed that the pressure curve of one station trends symmetrically to each other towards the both sides of a point on it, and this character had been used to predict the pressure trend. If the pressure values were predicted with considerable accuracy for several days ingeneral, the trends of pressure fields should be also predicted for several days. This work is very important to long-range forecasting.To examine whether there may be symmetry characters on the pressure curves or not, the symmetry points were usually looked for at first by the harmonic analysis of the original curves. But this method is not always effective because the original curves are usually very complicated to analyse them easily to some elementary waves. It is natural that the pressure trend correlates very closely to each other on the both sides of symmetry point. So if the points were found, with which the original curve has the above mentioned characters, that points may be considered as symmetry points.The author examined at first the pressure curve in the period Oct. 1928 to March 1929 in Tokyo, according to the symmetry index of each day in this period (by the Stumpf's method), and he found that the point which has considerable high symmetry index (for example. 90〈, 〈.10 or. 80〈, .20〉) for some period (for example 12, 18, 24 days etc.) may be considered also as the symmetry point for longer period (for example for a period several days longer than original period), and he could predict the pressure trend with considerable accuracy for several days according to this method.By the way it is also important to correct the prediction according to the differences between the real trend and the predicted trend from the symmetry point to now.The author applied this method to many points on the Eurasian continent in the period from Jan. to April 1940 and predicted the pressure trend on each of them, and ne could get considerable good results. So this method may be considered as effective for long rang forecasting if there are symmetry points on the perssure curves.Fig. 1 An example of symmetry point and symmetry phenomena on the pressure curve in Tokyo.Fig. 2 An example of the trend of symmetry index.Fig. 3 Comparison between the real and predicted trend of the pressure field.

[学科分类] 大气科学