NOTES AND CORRESPONDENCE Sensible Heat Observations Reveal Soil-Water Evaporation Dynamics
NOTES AND CORRESPONDENCE Sensible Heat Observations Reveal Soil-Water Evaporation Dynamics
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DOI：
10.1175/2007jhm963.1
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发表时间：
2008-02
期刊：
影响因子：
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通讯作者：
J. Heitman;R. Horton;T. DeSutter
中科院分区：
文献类型：
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作者：
J. Heitman;R. Horton;T. DeSutter
土壤水分蒸发在从微生物生态到大尺度气候的尺度上都很重要。然而，常规测量无法捕捉快速变化的近地表土壤热量和水分过程中涉及的土壤水分蒸发。本研究的目的是确定土壤中蒸发带的深度和位置。三针热脉冲传感器被用来监测土壤的热容量，导热系数，和温度低于裸露的土壤表面在中部爱荷华州在自然润湿/干燥周期。根据这些数据计算了土壤热通量和热储量的变化，以获得感热分量的平衡。从这个平衡的剩余，归因于潜热从水蒸发，提供了一个估计在原位土壤水分蒸发。随着降雨后土壤的干燥，土壤感热通量随深度的变化表现出发散性。热通量的发散指示与土壤-水蒸发相关的热汇的位置。蒸发估计从显热平衡提供的深度和时间模式与观测到的土壤-水枯竭模式一致。降雨后，土壤表面立即发生蒸发。降雨后6d内，蒸发带深入土壤剖面13 mm。蒸发速率在3毫米的深度达到峰值0.25毫米h-1。蒸发同时发生在多个测量的深度增量，但在土壤表面以下更深的深度的峰值蒸发率之间的时间滞后。土壤显热平衡精细测量技术的实施为提高对土壤水分蒸发的认识提供了新的机会。
Soil-water evaporation is important at scales ranging from microbial ecology to large-scale climate. Yet routine measurements are unable to capture rapidly shifting near-surface soil heat and water processes involved in soil-water evaporation. The objective of this study was to determine the depth and location of the evaporation zone within soil. Three-needle heat-pulse sensors were used to monitor soil heat capacity, thermal conductivity, and temperature below a bare soil surface in central Iowa during natural wetting/ drying cycles. Soil heat flux and changes in heat storage were calculated from these data to obtain a balance of sensible heat components. The residual from this balance, attributed to latent heat from water vaporization, provides an estimate of in situ soil-water evaporation. As the soil dried following rainfall, results show divergence in the soil sensible heat flux with depth. Divergence in the heat flux indicates the location of a heat sink associated with soil-water evaporation. Evaporation estimates from the sensible heat balance provide depth and time patterns consistent with observed soil-water depletion patterns. Immediately after rainfall, evaporation occurred near the soil surface. Within 6 days after rainfall, the evaporation zone proceeded 13 mm into the soil profile. Evaporation rates at the 3-mm depth reached peak values 0.25 mm h 1 . Evaporation occurred simultaneously at multiple measured depth increments, but with time lag between peak evaporation rates for depths deeper below the soil surface. Implementation of finescale measurement techniques for the soil sensible heat balance provides a new opportunity to improve understanding of soil-water evaporation.