The root-zone soil moisture spectrum in a mediterranean ecosystem
The root-zone soil moisture spectrum in a mediterranean ecosystem
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地中海生态系统根区土壤湿度谱
DOI：
10.1016/j.jhydrol.2022.127757
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发表时间：
2022
影响因子：
6.4
通讯作者：
Montaldo, Nicola
中科院分区：
文献类型：
--
作者：
Corona, Roberto;Katul, Gabriel;Montaldo, Nicola
根区土壤孔隙内的水储存会在土壤湿度动态中引入记忆效应，该效应比许多大气过程的积分时间尺度要长得多。因此，水文气候状态可以通过地表热量和水蒸气通量来“维持”，主要是因为它们可以“依赖”这种长期的土壤湿度记忆。根区土壤湿度记忆只是表征土壤湿度动态谱的一个特征，这里使用长期测量和模型的组合来分析这一特征。特别是，使用 14 年每半小时的测量结果来检查地中海生态系统中根区土壤水分含量的范围。这种生态系统的一个显着的水文气候特征是土壤水分的来源（主要是降雨）和汇（主要是蒸散量）彼此大致不同步。对于超过 4 个十年的时间尺度和超过 7 个十年的能量，测量的土壤湿度谱的规范形状显示为近似洛伦兹形状，由土壤湿度方差及其记忆决定，但有两个例外：在日到日时间尺度上出现峰值，在近年时间尺度上出现较弱的峰值。模型计算和光谱分析表明，导致蒸散量变化的水文气候强迫的昼夜和季节变化对土壤水分光谱的标准化形状影响较小。然而，它们的影响是通过时间方差的调整来体现的。这些发现表明，降水而不是蒸散变化主导着土壤湿度变化的多尺度特性，与之前的气候模型模拟一致。此外，由土壤湿度年峰值（340 d）推断的土壤湿度记忆与气候模型模拟一致，而线性质量平衡方法的损失函数评估的记忆值较小（50 d），凸显了弱非平稳性对土壤水分变异的影响。
Storage of water within soil pores of the root zone introduce memory effects in the dynamics of soil moisture that are considerably longer than the integral timescale of many atmospheric processes. Thus, hydro-climatic states can be “sustained” through land-surface heat and water vapor fluxes primarily because they can “feed off” on this long-term soil moisture memory. Root-zone soil moisture memory is only but one feature characterizing the spectrum of soil moisture dynamics, which is analyzed here using a combination of long-term measurements and models. In particular, the spectrum of root-zone soil moisture content in a Mediterranean ecosystem is examined using 14-years of half-hourly measurements. A distinguishing hydro-climatic feature in such ecosystems is that sources (mainly rainfall) and sinks (mainly evapotranspiration) of soil moisture are roughly out of phase with each other. For over 4 decades of time scales and 7 decades of energy, the canonical shape of the measured soil moisture spectrum is shown to be approximately Lorentzian determined by the soil moisture variance and its memory but with two exceptions: the occurrences of a peak at diurnal-to-daily time scales and a weaker peak at near annual time scales. Model calculations and spectral analysis demonstrate that diurnal and seasonal variations in hydroclimate forcing responsible for variability in evapotranspiration had minor impact on the normalized shape of the soil moisture spectrum. However, their impact was captured by adjustments in the temporal variance. These findings indicate that precipitation and not evapotranspiration variability dominates the multi-scaling properties of soil moisture variability consistent with prior climate model simulations. Furthermore, the soil moisture memory inferred by the annual peak of soil moisture (340 d) is consistent with climate model simulations, while the memory evaluated from the loss function of a linearized mass balance approach leads to a smaller value (50 d), highlighting the effect of weak non-stationarity on soil moisture variability.