Campus Units

Agronomy

Document Type

Article

Publication Version

Published Version

Publication Date

8-2017

Journal or Book Title

Journal of Hydrometeorology

Volume

18

Issue

8

First Page

2285

Last Page

2295

DOI

10.1175/JHM-D-16-0290.1

Abstract

In the gradient method, soil heat flux density at a known depth G is determined as the product of soil thermal conductivity λ and temperature T gradient. While measuring λ in situ is difficult, many field studies readily support continuous, long-term monitoring of soil T and water content θ in the vadose zone. In this study, the performance of the gradient method is evaluated for estimating near-surface G using modeled λ and measured T. Hourly λ was estimated using a model that related λ to θ, soil bulk density ρb, and texture at 2-, 6-, and 10-cm depths. Soil heat flux Gm was estimated from modeled λ and measured T gradient (from thermocouples). The Gm results were evaluated with heat flux data GHP determined using independent measured λ and T gradient from heat-pulse probes. The λ model performed well at the three depths with 3.3%–7.4% errors. The Gm estimates were similar to GHP (agreed to within 15.1%), with the poorest agreement at the 2-cm soil depth, which was caused mainly by the relatively greater variability in ρb. Accounting for temporal variations in ρb (with core method) improved the accuracies of λ and Gm at the 2-cm depth. Automated θ monitoring approaches (e.g., time domain reflectometry), rather than gravimetric sampling, captured the temporal dynamics of near-surface λ and G well. It is concluded that with continuous θ and T measurements, the λ model–based gradient method can provide reliable near-surface G. Under conditions of soil disturbance or deformation, including temporally variable ρb, data improves the accuracy of G data.

Comments

This article is published as Peng, Xiaoyang, Joshua Heitman, Robert Horton, and Tusheng Ren. "Determining near-surface soil heat flux density using the gradient method: A thermal conductivity model–based approach." Journal of Hydrometeorology 18, no. 8 (2017): 2285-2295. doi: 10.1175/JHM-D-16-0290.1. Posted with permission.

Rights

© Copyright 2017 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17 USC §108) does not require the AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a website or in a searchable database, or other uses of this material, except as exempted by the above statement, requires written permission or a license from the AMS. All AMS journals and monograph publications are registered with the Copyright Clearance Center (http://www.copyright.com). Questions about permission to use materials for which AMS holds the copyright can also be directed to permissions@ametsoc.org. Additional details are provided in the AMS Copyright Policy statement, available on the AMS website (http://www.ametsoc.org/CopyrightInformation).

Copyright Owner

American Meteorological Society

Language

en

File Format

application/pdf

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