On the Prediction of Air Temperature

[摘要] Three methods to predict air temperature were discussed. The first is the method of extrapolation, the second is that of air mass analysis and the last calculating method. These methods were applied to the daily air temperature prediction at Tokyo, and good results were obtained. The methods summarizedas follows.(1) The method of extrapolation. An assumption was made that diurnal change of the temperature is given byθ(t)=θ0+Af(t)where A is a constant depending on the weather, ƒ a certain definite function of one day period. And the assumption was proved to hold fairly well except in some special case, such as sharp discontinuity of the temperature exists in the atmosphere. Assuming these, the future temperatures are calculated from observced temperatures at two time points, and rapidly calculating method by graph was proposed.(2) The method of air mass analysis. Firstly it was shown that the change of the air temperature was accompanied with the change of vapour tension in the atmosphere, and nextly it was found that the night minimum temperature as well as maximum temperature was determined by the vapour tension and the weather. Hence, by predicting futrue weather and vapour tension, the future maximum and minimum temperature are calculated. The vapour tension is one of the conservative quantities of an air mass, and the prediction is comparatively easy.Further, theoretical consideration of the above method was made. The energy transfer at the immediate neigbourhood of the ground is expressed approximately byLA(emax-e=LA{e(T)-e}={Js+σT4(0·474-0·075_??_)} where left hand side is the energy due to evaporation, the right hand side the energy due to solar and effective radiations. And it is easily concluded that the temperature is the function only of weather and vapour tension.(3) Calculating method. From the theoretical consideration of the diurnal variation of the temperature, the following equations are derived.δT=N_??_T4 where ΔT is the rate of cooling in night, andδT_??_=Js/1+v/v0 where ΔT' is the rate of heating in day time. And the constants in above equations at Tokyo were determined.

[学科分类] 大气科学