大气随机动力学与可预报性

偶然性与必然性过程及其相互转化是世界事物变化复杂性的根源。根据布朗运动统计理论,提出了分子热运动是不稳定流体中湍流形成之源,由此形成不同宏观尺度的随机运动是大气运动固有的属性。观测事实表明,太阳辐射作为决定大气运动与变化的主要因子,它的变化具有随机性,是大气的随机强迫因子,它对气候变化具有决定性影响。地-气相互作用是一个时变的非线性相互反馈的耦合过程,形成了下边界对大气复杂的随机强迫作用,其界面交换耦合随机动力学模式尚待建立。由于大气过程固有的随机性以及随机的外强迫耦合作用,大气确定性预报的时效是有界的,它决定于预报对象的不确定性及其空间尺度与时间尺度,以及预报时效内的大气不确定性。由此,客观存在着大气过程的报不准关系。

ATMOSPHERIC STOCHASTIC DYNAMICS AND PREDICTABILITY

Stochastic and determined processes and their inter-transformation are the sources for the complexity of the variations in the world.According to the statistical theory of Brownian motions,it is issued that turbulences in the unstable fluid motions are caused by the molecule thermodynamic motions and produce the stochastic motions in various macroscales,which are the nature of the atmospheric motions.Observations have shown that the solar radiation,the main factor determining the atmospheric motions and changes,varies in random,so it is a stochastic external forcing on the atmosphere and has dominant impact on the climate change.Air-land interaction,a time-varying coupling process with nonlinear feedback,forms the complex random external forcing on the atmosphere in the lower boundary,but the stochastic coupling dynamic model of the exchange in the interface is not set up yet.Owing to the chaotic nature of the atmospheric motions and all the stochastic external forcing factors,the determining prediction of the atmospheric motions is only valid in limited time range,which is determined by the uncertainty in the predicted subject and its temporal and spatial scale,and the uncertainty in the atmospheric motions.Therefore,unpredictability is objective in the atmospheric motions.