Investigating the Coupling Relationship between Soil Moisture and Evaporative Fraction over China’s Transitional Climate Zone

IF 3.1 Q2 WATER RESOURCES

Hydrology Pub Date : 2023-11-24 DOI:10.3390/hydrology10120221

Liang Zhang, Sha Sha, Qiang Zhang, Funian Zhao, Jianhua Zhao, Hongyu Li, Sheng Wang, Jianshun Wang, Yanbin Hu, Hui Han

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Abstract

The interaction between soil moisture (SM) and evaporative fraction (EF), which reflects the degree of exchange of water and energy between the land and the atmosphere, is an important component of the theory of land–atmosphere coupling. Exploring the relationship between SM and EF in the transitional climate zone of China can help deepen our understanding of the characteristics of water and energy exchange in this region of strong land–atmosphere coupling. Data on observations in fluxes in the transitional climate zone revealed that fluxes in the energy on the surface of the land in this region exhibited significant inter-annual variations. The sensible heat flux (SH) exhibited the largest fluctuations in July and August, while the latent heat flux (LE) varied the most from June to August. The EF was found to exhibit weak correlations with indicators of vegetation growth such as the leaf area index, Normalized Difference Vegetation Index, and gross primary productivity in the transitional zone of the East Asian summer monsoon. By contrast, the relationship of land–atmosphere coupling between EF and SM in the transitional climate zone was stronger. Based on an analysis of the consistency of the relationship of SM-EF coupling, when the SMP reached 35%, there was a significant transition in the linear relationship between the SMP and EF that was consistent between the shallower and deeper layers of soil (0–40 and 40–80 cm). However, neither level had SM that reached saturation during the six-year observational period (2007–2012), and the mean values of its probability density function showed that the deep soil was drier than the shallow soil. This characteristic shows that SM plays a dominant role in variations in the EF in the transitional climate zone, which in turn indicates that constraints on the moisture govern the SM–EF relationship. The results of this study provide a better understanding of the mechanisms of land–atmosphere coupling in the transitional climate zone of China.

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中国过渡气候区土壤水分与蒸发分的耦合关系研究

土壤水分（SM）与蒸发分（EF）之间的相互作用反映了陆地与大气之间的水能交换程度，是陆气耦合理论的重要组成部分。探讨中国过渡气候带的蒸发分量（SM）与蒸发分量（EF）之间的关系，有助于加深我们对这一陆地-大气强耦合区域水和能量交换特征的认识。过渡气候带通量观测数据显示，该地区陆地表面能量通量呈现出显著的年际变化。显热通量（SH）在 7 月和 8 月的波动最大，而潜热通量（LE）在 6 月至 8 月的变化最大。研究发现，EF 与东亚夏季季风过渡带的植被生长指标（如叶面积指数、归一化差异植被指数和总初级生产力）相关性较弱。相比之下，过渡气候区 EF 与 SM 之间的陆地-大气耦合关系更强。根据土壤-大气耦合关系的一致性分析，当 SMP 达到 35% 时，SMP 与 EF 之间的线性关系出现了明显的过渡，这种过渡在较浅和较深的土壤层（0-40 cm 和 40-80 cm）之间是一致的。然而，在六年的观测期内（2007-2012 年），这两层土壤的 SM 均未达到饱和，其概率密度函数的平均值显示深层土壤比浅层土壤更干燥。这一特征表明，SM 在过渡气候区 EF 的变化中起着主导作用，这反过来又表明，水分的约束条件制约着 SM 与 EF 的关系。该研究结果有助于更好地理解中国过渡气候带的陆地-大气耦合机制。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Hydrology Earth and Planetary Sciences-Earth-Surface Processes

CiteScore

4.90

自引率

21.90%

发文量

192

审稿时长

6 weeks

期刊介绍： Journal of Hydrology publishes original research papers and comprehensive reviews in all the subfields of the hydrological sciences, including water based management and policy issues that impact on economics and society. These comprise, but are not limited to the physical, chemical, biogeochemical, stochastic and systems aspects of surface and groundwater hydrology, hydrometeorology, hydrogeology and hydrogeophysics. Relevant topics incorporating the insights and methodologies of disciplines such as climatology, water resource systems, ecohydrology, geomorphology, soil science, instrumentation and remote sensing, data and information sciences, civil and environmental engineering are within scope. Social science perspectives on hydrological problems such as resource and ecological economics, sociology, psychology and behavioural science, management and policy analysis are also invited. Multi-and interdisciplinary analyses of hydrological problems are within scope. The science published in the Journal of Hydrology is relevant to catchment scales rather than exclusively to a local scale or site. Studies focused on urban hydrological issues are included.