Campus Units
Agronomy
Document Type
Article
Publication Version
Published Version
Publication Date
2-2008
Journal or Book Title
Journal of Hydrometeorology
Volume
9
Issue
1
First Page
165
Last Page
171
DOI
10.1175/2007JHM963.1
Abstract
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.
Rights
Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted.
Language
en
File Format
application/pdf
Recommended Citation
Heitman, J. L.; Horton, R.; Sauer, T. J.; and DeSutter, T. M., "Sensible Heat Observations Reveal Soil-Water Evaporation Dynamics" (2008). Agronomy Publications. 380.
https://lib.dr.iastate.edu/agron_pubs/380
Comments
This article is published as Heitman, J. L., Robert Horton, T. J. Sauer, and T. M. DeSutter. "Sensible heat observations reveal soil-water evaporation dynamics." Journal of Hydrometeorology 9, no. 1 (2008): 165-171. doi: 10.1175/2007JHM963.1. Posted with permission.