摘要:
对1952—1980年我国连续的月地面气温用时间序列ARMA(p、q)模型进行随机建模。月温度由60个站组成,用经验正交函数加以展开,取不同的样本长度即348,336和300月,以便考察经验正交展开的稳定性。前四个主成分,即z1,z2,z3,z4取为多维时间序列的变数,因为它们的总方差贡献达99.26%。在这四个主成分序列中的决定性周期用周期图和最大熵方法加以揭露。对一维变量zi,(i=1,2,3,4)的ARMA(p,q)的模型识别用Pandit-Wu方法进行,这样就可求得实验模型。用zi模型的外推值来预报月温度场。距平预报的命中率评分为78.3%,高于目前的业务长期天气预报。
Abstract:
For designing a time series of the successive monthly surface temperature in 1952-1980 over China a stochastic model is formulated by an AEMA (p, q) model. The monthly temperature fields composed of records at 60 stations are expanded by means of EOF (Empirical Orthogonal Function) with the various sample sizes 348, 336 and 300 months so as to examine the stability of EOF expansion. Then the first four principal components, i. e. z1, z2, z3, z4 are taken as the variables of multivariate time series, since their total variance contribution is 99.26%. The major periods in first four principal components series are also revealed by using the periodogram and the maximum entropy method. The model identification of ARMA (p,q) for univariate variables zi (i=1,2,3,4) is made by the Pandit-Wu method, Then, the empirical models are obtained. The extrapolations of s models are used for predicting a monthly temperature field. The score of hit ratio of departure forecasts is 78.3%, which is better than that of the recent operational long-range weather forecast.