平均环流的诊断与预报

本文采用实际的大气资料分析了一个正压平均环流距平模式各项的相对重要性.结果表明,单纯考虑初始场的惯性预报的准确率随所取平均时间的增加而迅速下降,并以长波和超长波段最为显著. 加上气候平均风场及地球球面效应等动力因子后的修正的惯性预报,其结果不如纯惯性预报好.而且,所取的平均时间越长,效果越差.加进散度订正因子后,对长波和超长波的预报起明显改进作用, 对平均环流的预报起重要作用的因子是未知的强迫作用项.根据分析,本文提出了提高平均环流预报准确率的可能途径.

Diagnoses and Predictions of Time-averaged Circulations

A barotropic linear model is developed for time- averaged circulation forecasts. The relative contribution from each factor is analysed using observation data . It is shown that the accuracy of the persistence scheme in which the initial state alone is included drops rapidly with the increase of the mean time , especially for the planetary waves .The modified persistence scheme in which the dynamical processes of the advection and the spherical effect of the earth are taken into account of is not better than the pure persistence . The longer the mean time , the worse the results . The decrease of pattern correlations occur at almost all wave numbers. When the divergence correction is taken into account, the results are considerably improved for the planetary and long waves .The crucial factor for improving the prediction is the unknown forcing. The possible approaches of improving time- averaged circulation forecasts are also proposed in this paper .