Park Jeryang, Rao P Suresh C
School of Urban and Civil Engineering, Hongik University, Seoul, 121-784, South Korea; School of Civil Engineering, Purdue University, West Lafayette, IN 47907, USA.
School of Civil Engineering, Purdue University, West Lafayette, IN 47907, USA; Agronomy Department, Purdue University, West Lafayette, IN 47907, USA.
J Contam Hydrol. 2014 Nov 15;169:112-122. doi: 10.1016/j.jconhyd.2014.08.005. Epub 2014 Aug 24.
We present here a conceptual model and analysis of complex systems using hypothetical cases of regime shifts resulting from temporal non-stationarity in attractor strengths, and then present selected published cases to illustrate such regime shifts in hydrologic systems (shallow aquatic ecosystems; water table shifts; soil salinization). Complex systems are dynamic and can exist in two or more stable states (or regimes). Temporal variations in state variables occur in response to fluctuations in external forcing, which are modulated by interactions among internal processes. Combined effects of external forcing and non-stationary strengths of alternative attractors can lead to shifts from original to alternate regimes. In systems with bi-stable states, when the strengths of two competing attractors are constant in time, or are non-stationary but change in a linear fashion, regime shifts are found to be temporally stationary and only controlled by the characteristics of the external forcing. However, when attractor strengths change in time non-linearly or vary stochastically, regime shifts in complex systems are characterized by non-stationary probability density functions (pdfs). We briefly discuss implications and challenges to prediction and management of hydrologic complex systems.
我们在此展示一个概念模型，并利用吸引子强度的时间非平稳性导致状态转变的假设案例，对复杂系统进行分析，然后展示一些已发表的案例，以说明水文系统中的此类状态转变（浅水水生生态系统；地下水位变化；土壤盐渍化）。复杂系统是动态的，可以存在于两种或更多种稳定状态（或 regime）中。状态变量的时间变化是对外部强迫波动的响应，而外部强迫波动又受到内部过程之间相互作用的调节。外部强迫和替代吸引子的非平稳强度的综合效应可能导致从原始状态向替代状态的转变。在具有双稳态的系统中，当两个相互竞争的吸引子的强度在时间上保持恒定时，或者是非平稳但以线性方式变化时，状态转变在时间上是平稳的，并且仅由外部强迫的特征控制。然而，当吸引子强度随时间非线性变化或随机变化时，复杂系统中的状态转变具有非平稳概率密度函数（pdfs）的特征。我们简要讨论了对水文复杂系统预测和管理的影响及挑战。
