MOS方法在动力延伸期候平均气温预报中的应用

摘要

利用1982年1月-2010年3月动力延伸预报产品及宁夏候平均气温,采用逐步回归的MOS统计方法,预报宁夏24个测站未来40 d逐候平均气温,为了对比模式直接输出结果与资料按月和按季节划分建立的MOS方法预报效果,对2009年和2010年1-3月的预报效果分别进行了对比检验.结果表明:MOS预报效果较模式直接输出有显著提高;不同时段的资料划分,不同的建模样本长度,都会使MOS预报效果产生差异.虽然利用按季节划分的资料所建立的MOS方程样本数明显多于按月划分的样本数,但由于按月划分的资料所选择的预报因子更能集中反映这一时段预报对象的相关性,物理意义更为明确,因而预报效果较好;对于同样按月划分的MOS方法而言,样本数越多,温度预报的效果越好,稳定性越强;进一步检验该方法对极端候平均气温的预报能力,出现极端气温时,该方法能够预报出气温剧烈变化的趋势和变温幅度,并随着预报时效临近逐步订正,误差值逐渐减小,预报结果可作为中期业务预报的参考.%Stepwise regression MOS statistical method is applied to predict the pentad mean temperature of future 40 days at 24 weather stations in Ningxia, using the pentad mean temperature and dynamical extended range forecasting products from January 1982 to March 2010. In order to evaluate the predicting capability of the direct numerical model output products (DMO) and MOS which use the seasonal and monthly data,the prediction results of DMO and MOS from January to March in 2009 and 2010 are compared.The prediction accuracy and stability of MOS improved remarkably comparing with DMO, MOS method can predict the trend and extent of violent weather changes in temperature. With the drawing near of predicting time and successive correction, its prediction error values decreases gradually, and predicting resuits can be for the reference of medium term prediction operation.MOS prediction capability is different when using data of different lengths. The prediction capability of MOS using monthly data is better, because the chosen prediction factors using monthly data can better indicate the correlation of prediction objects in this period, and its physical meaning is much distinct. So more monthly data samples lead to better temperature prediction result and stability.MOS method merely applies the output products of dynamical extended range prediction model, so its prediction results thoroughly rely on the accuracy and stability of numerical prediction model. The prediction results may be more accurate if some observation factor, local experimental factor and climatic factorare added.There are 4 aspects which need attentions when establishing MOS equations: The equations should be established based on experimental calculating error values; the establishment of F test value at each weather station should also consider experimental calculating error values; using data samples of longer temporal scales to verify if MOS prediction results will be better using more monthly data samples; finally, more new data are recommended to improve MOS prediction capability in the future.