理解大气资料同化的根本概念

本文阐明随机变量是大气资料同化的根本概念。其根本性可以体现在两个方面：(1) 原理上，大气资料同化的科学实质是建立在随机变量这个概念上。由于将资料同化的可用信息视为随机变量的数据，所以概率论与数理统计学成为资料同化的数学基础，使得资料同化有了基于估计理论的最优标准及其数学形式，成为一门科学。(2) 实施上，基于随机变量这个概念下的数据是理解大气资料同化发展史的钥匙。由于资料同化的具体实施表现为各种同化方法中可用信息的资料融合，将资料同化的可用信息视为随机变量的数据，可以清晰地揭示主流同化方法的发展进程对应着其可用信息在内涵和种类上的不断扩展，这个扩展具体地体现了同化发展史的一个循序渐进的内在发展逻辑。

Understanding of the Fundamental Concept of Atmospheric Data Assimilation

What is it that makes atmospheric data assimilation come to be a discipline with its own theoretically mathematical foundation and formalism? In this article it is highlighted that the random variable is the fundamental concept of atmospheric data assimilation. This lies in two aspects. First, probability theory and mathematical statistics, which are oriented to random variables, can be used as the mathematical foundation of atmospheric data assimilation, and thus atmospheric data assimilation is equipped with its mathematical formalism which is derived from its criterion for an optimal estimate on the basis of estimation theory. So in this sense the essence of science for atmospheric data assimilation is built on the concept of random variable. Second, data under the concept of random variable can find a way to understand the clear step by step expansion of useful information contents used during the historical progress of atmospheric data assimilation, which helps to know a simple cognitional intrinsic logic of development of atmospheric data assimilation.