Multiple hydrological attractors under stochastic daily forcing: 1. Can multiple attractors exist?
Multiple hydrological attractors under stochastic daily forcing: 1. Can multiple attractors exist?
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随机日强迫下的多个水文吸引子： 1. 可以存在多个吸引子吗？
DOI：
10.1002/2012wr013003
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发表时间：
2014
影响因子：
5.4
通讯作者：
A. Western
中科院分区：
文献类型：
--
作者：
T. Peterson;A. Western
最近的研究表明，在水文模型中包含正反馈会导致具有多个稳态的复杂行为。当在这样的模型中模拟一个大的扰动，比如一场大干旱时，水文就会发生变化。一旦扰动结束，水文学就不会回到扰动之前的状态，而是持续在另一种状态中。这些多个稳态(此后的吸引子)存在于单个模型的参数化中，并且使得系统对这种瞬时扰动具有有限的恢复能力。过去的水文复原力研究的一个局限性是，通过平均年或月平均强迫来确定多个吸引子。考虑到大多数水文通量都具有显著的强迫随机性，并且不是在如此大的时间尺度上运行，当流域受到随机日强迫时，是否可以存在多个水文吸引子仍然是一个悬而未决的问题。这一问题是本文研究的重点，也是在野外寻找多个水文吸引子之前需要解决的问题。为研究这一问题，采用了一个半分布式的山坡生态水文模型，该模型在月平均气候强迫作用下表现出多个稳态。本文利用生态水文学模型研究了在每日随机强迫作用下，植被与咸水层之间的反馈是否会导致两个吸引子的存在。用一种新的极限环延续技术量化了吸引子和它们之间的阈值(此后)，该技术将气候强迫从每日提升到每月(模型和极限环代码免费可用)。该方法用于确定存在多个吸引子的饱和侧向导水率的值。然后，根据时间综合估计对这些估计进行了评估，他们同意这一估计。总体而言，在随机日强迫作用下，存在多个吸引子。然而，将气候强迫从每月改变为每天，确实显著地缩小了存在两个吸引子的参数范围。这表明，拥有多个吸引子的集水区可能比之前认为的要少。
Including positive feedbacks in hydrological models has recently been shown to result in complex behavior with multiple steady states. When a large disturbance, say a major drought, is simulated within such models the hydrology changes. Once the disturbance ends the hydrology does not return to that prior to the disturbance, but rather, persists within an alternate state. These multiple steady states (henceforth attractors) exist for a single model parameterization and cause the system to have a finite resilience to such transient disturbances. A limitation of past hydrological resilience studies is that multiple attractors have been identified using mean annual or mean monthly forcing. Considering that most hydrological fluxes are subject to significant forcing stochasticity and do not operate at such large timescales, it remains an open question whether multiple hydrological attractors can exist when a catchment is subject to stochastic daily forcing. This question is the focus of this paper and it needs to be addressed prior to searching for multiple hydrological attractors in the field. To investigate this, a previously developed semidistributed hillslope ecohydrological model was adopted which exhibited multiple steady states under average monthly climate forcing. In this paper, the ecohydrological model was used to explore if feedbacks between the vegetation and a saline water table result in two attractors existing under daily stochastic forcing. The attractors and the threshold between them (henceforth repellor) were quantified using a new limit cycle continuation technique that upscaled climate forcing from daily to monthly (model and limit cycle code is freely available). The method was used to determine the values of saturated lateral hydraulic conductivity at which multiple attractors exist. These estimates were then assessed against time‐integration estimates, which they agreed with. Overall, multiple attractors were found to exist under stochastic daily forcing. However, changing the climate forcing from monthly to daily did significantly reduce the parameter range over which two attractors existed. This suggests fewer catchments may have multiple attractors than previously considered.