Climate sensitivities via a Fokker–Planck adjoint approach
Climate sensitivities via a Fokker–Planck adjoint approach
复制标题
通过福克-普朗克伴随方法计算气候敏感性
DOI：
--
复制
发表时间：
2005
期刊：
影响因子：
--
通讯作者：
J. Thuburn
中科院分区：
文献类型：
--
作者：
J. Thuburn
利用气候模型计算特定气候诊断对某些输入参数的敏感性的传统方法是对参数的控制值和扰动值进行气候模型的积分。但是，当需要对许多参数的诊断灵敏度时，这种方法变得非常昂贵。由于需要更便宜地计算这种灵敏度，这里开发了一种新方法。从理论上讲，它是基于考虑气候是由满足相关稳态Fokker-Planck方程的概率密度函数来描述的。气候敏感性（即诊断值相对于输入参数的导数）可以用稳定的Fokker-Planck方程的伴随解来表示。这种伴随解可以在实践中通过气候模式积分的集合来计算。目前，该理论仅对包含随机强迫的气候模式有效。给出了两种基于新理论的方法的实例，并将其应用于著名的洛伦兹方程的随机版本。然而，要获得一种在计算上适用于完整气候模式的方法，还需要进一步改进。版权所有©2005英国皇家气象学会
The traditional method for computing the sensitivity of a particular climate diagnostic to some input parameter, using a climate model, is to carry out integrations of the climate model for control and perturbed values of the parameter. However, when the sensitivity of the diagnostic to many parameters is required, this method becomes very expensive. Motivated by the need to calculate such sensitivities more cheaply, a new approach is developed here. Theoretically, it is based on considering the climate to be described by the probability density function that satisfies the relevant steady Fokker–Planck equation. The climate sensitivity (i.e. the derivative of the diagnostic with respect to the input parameters) can then be expressed in terms of the solution of the adjoint of the steady Fokker–Planck equation. This adjoint solution could be computed in practice via an ensemble of climate model integrations. Currently the theory is valid only for climate models that include stochastic forcing. A practical demonstration is given of two methods based on the new theory, applied to a stochastic version of the famous Lorenz equations. Some further refinements are needed, however, to achieve a method that would be computationally practicable for a full climate model. Copyright © 2005 Royal Meteorological Society