Title: On the surface energy balance closure at different temporal scales

Abstract

Measurements of the surface energy fluxes (turbulent and radiative) and other ancillary atmospheric/soil parameters made in the Columbia River Basin (Oregon) in an area of complex terrain during a 10-month long portion of the second Wind Forecast Improvement Project (WFIP 2) field campaign are used to study the surface energy budget (SEB) and surface fluxes over different temporal scales. This study analyzes and discusses SEB closure based on half-hourly, daily, monthly, seasonal, and sub-annual (~10-month) temporal averages. The data were collected over all four seasons for different states of the underlying ground surface (dry, wet, and frozen). Our half-hourly direct measurements of energy balance show that the sum of the turbulent sensible and latent heat fluxes systematically underestimate positive net radiation by around 20–30% during daytime and overestimate negative net radiation at night. This imbalance of the surface energy budget is comparable to other terrestrial sites. However, on average, the residual energy imbalance is significantly reduced at daily, weekly, and monthly averaging timescales, and moreover, the SEB can be closed for this site within reasonable limits on seasonal and sub-annual timescales (311-day averaging for the entire field campaign dataset). Increasing the averaging time to daily and longer time intervals substantiallymore » reduces the ground heat flux and storage terms, because energy locally entering the soil, air column, and vegetation in the morning is released in the afternoon and evening. Averaging on daily to sub-annual timescales also reduces random instrumental measurement errors and other uncertainties as well as smooths out a hysteresis effect (phase lag) in the SEB relationship between different components. This study shows that SEB closure is better for dry soils compared to wet soils and the statistical dependence of the turbulent fluxes and net radiation for freezing soil surfaces appears weak, if not non-existent, apparently due to lack of the latent heat of fusion term in the traditional SEB equation.« less

Authors:

Grachev, Andrey A.  ^[1];

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Fairall, Christopher W. ^[2]; Blomquist, Byron W. ^[1]; Fernando, Harindra J.S. ^[3]; Leo, Laura S. ^[3]; Otárola-Bustos, Sebastián F. ^[3]; Wilczak, James M. ^[2]; McCaffrey, Katherine L. ^[1]

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+ Show Author Affiliations

1. NOAA Earth System Research Lab., Boulder, CO (United States); Univ. of Colorado, Boulder, CO (United States)
2. NOAA Earth System Research Lab., Boulder, CO (United States)
3. Univ. of Notre Dame, IN (United States)

Publication Date:

Thu Oct 31 00:00:00 EDT 2019

Research Org.:

National Oceanic and Atmospheric Administration (NOAA), Boulder, CO (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Wind Energy Technologies Office

OSTI Identifier:

1799309

Alternate Identifier(s):

OSTI ID: 1632713

Grant/Contract Number:  

EE0007605; FOA-0000984

Resource Type:

Accepted Manuscript

Journal Name:

Agricultural and Forest Meteorology

Additional Journal Information:

Journal Volume: 281; Journal ID: ISSN 0168-1923

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; energy balance closure; radiative fluxes; surface energy budget; time averaging; turbulent fluxes