Estimation of surface heat flux and an index of soil moisture using adjoint-state surface energy balance

Abstract. The sensitivity of climate simulations to the diurnal variation in surface energy budget encourages enhanced inspection into the energy balance closure failure encountered in micrometeorological experiments. The diurnal wave phases of soil surface heat flux and temperature are theoretically characterized and compared for both moist soil and absolute dry soil surfaces, indicating that the diurnal wave phase difference between soil surface heat flux and temperature ranges from 0 to π/4 for natural soils. Assuming net radiation and turbulent heat fluxes have identical phase with soil surface temperature, we evaluate potential contributions of the wave phase difference on the surface energy balance closure. Results show that the sum of sensible heat flux (H) and latent heat flux (LE) is always less than surface available energy (Rn-G0) even if all energy components are accurately measured, their footprints are strictly matched, and all corrections are made. The energy balance closure ratio (ε) is extremely sensitive to the ratio of soil surface heat flux amplitude (A4) to net radiation flux amplitude (A1), and large value of A4/A1 causes a significant failure in surface energy balance closure. An experimental case study confirms the theoretical analysis.

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Estimation of Hourly Land Surface Heat Fluxes over the Tibetan Plateau by the Combined Use of Geostationary and Polar Orbiting Satellites

10.5194/acp-2018-1165 ◽

2018 ◽

Author(s):

Lei Zhong ◽

Yaoming Ma ◽

Zeyong Hu ◽

Yunfei Fu ◽

Yuanyuan Hu ◽

...

Keyword(s):

Heat Flux ◽

Energy Balance ◽

Surface Energy ◽

Land Surface ◽

Surface Energy Balance ◽

Surface Heat ◽

Heat Fluxes ◽

The Tibetan Plateau ◽

Surface Heat Fluxes ◽

Land Surface Heat Fluxes

Abstract. The estimation of land surface heat fluxes has significant meaning for energy and water cycle studies, especially for the Tibetan Plateau (TP), which has unique topography and strong land–atmosphere interactions. The land surface heating status also directly influences the movement of atmospheric circulation. However, for a long time, plateau-scale land surface heat flux information with high temporal resolution has been lacking, which greatly limits understanding of diurnal variations in land–atmosphere interactions. Based on geostationary and polar orbiting satellite data, a surface energy balance system (SEBS) was used in this paper to derive hourly land surface heat fluxes with a spatial resolution of 10 km. Six stations scattered through the TP and equipped for flux tower measurements were used to correct the energy imbalance problem existing in the measurements and to perform cross-validation. The results showed good agreement between derived fluxes and in situ measurements through 3738 validation samples. The RMSEs for net radiation flux, sensible heat flux, latent heat flux and soil heat flux were 76.63 W m−2, 60.29 W m−2, 64.65 W m−2 and 37.5 W m−2, respectively. The derived results were also found to be superior to GLDAS flux products (RMSEs for the surface energy balance components were 114.32 W m−2, 67.77 W m−2, 75.6 W m−2 and 40.05 W m−2, respectively). The diurnal and seasonal cycles of land surface energy balance components were clearly identified. Their spatial distribution was found to be consistent with the heterogeneous land surface status and general hydrometeorological conditions of the TP.

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Estimation of hourly land surface heat fluxes over the Tibetan Plateau by the combined use of geostationary and polar-orbiting satellites

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-5529-2019 ◽

2019 ◽

Vol 19 (8) ◽

pp. 5529-5541 ◽

Cited By ~ 10

Author(s):

Lei Zhong ◽

Yaoming Ma ◽

Zeyong Hu ◽

Yunfei Fu ◽

Yuanyuan Hu ◽

...

Keyword(s):

Heat Flux ◽

Energy Balance ◽

Surface Energy ◽

Land Surface ◽

Surface Energy Balance ◽

Surface Heat ◽

Heat Fluxes ◽

The Tibetan Plateau ◽

Surface Heat Fluxes ◽

Land Surface Heat Fluxes

Abstract. Estimation of land surface heat fluxes is important for energy and water cycle studies, especially on the Tibetan Plateau (TP), where the topography is unique and the land–atmosphere interactions are strong. The land surface heating conditions also directly influence the movement of atmospheric circulation. However, high-temporal-resolution information on the plateau-scale land surface heat fluxes has been lacking for a long time, which significantly limits the understanding of diurnal variations in land–atmosphere interactions. Based on geostationary and polar-orbiting satellite data, the surface energy balance system (SEBS) was used in this paper to derive hourly land surface heat fluxes at a spatial resolution of 10 km. Six stations scattered throughout the TP and equipped for flux tower measurements were used to perform a cross-validation. The results showed good agreement between the derived fluxes and in situ measurements through 3738 validation samples. The root-mean-square errors (RMSEs) for net radiation flux, sensible heat flux, latent heat flux and soil heat flux were 76.63, 60.29, 71.03 and 37.5 W m−2, respectively; the derived results were also found to be superior to the Global Land Data Assimilation System (GLDAS) flux products (with RMSEs for the surface energy balance components of 114.32, 67.77, 75.6 and 40.05 W m−2, respectively). The diurnal and seasonal cycles of the land surface energy balance components were clearly identified, and their spatial distribution was found to be consistent with the heterogeneous land surface conditions and the general hydrometeorological conditions of the TP.

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Analysing surface energy balance closure and partitioning over a semi-arid savanna FLUXNET site in Skukuza, Kruger National Park, South Africa

Hydrology and Earth System Sciences ◽

10.5194/hess-21-3401-2017 ◽

2017 ◽

Vol 21 (7) ◽

pp. 3401-3415 ◽

Cited By ~ 18

Author(s):

Nobuhle P. Majozi ◽

Chris M. Mannaerts ◽

Abel Ramoelo ◽

Renaud Mathieu ◽

Alecia Nickless ◽

...

Keyword(s):

Heat Flux ◽

Energy Balance ◽

Surface Energy ◽

Latent Heat ◽

Surface Energy Balance ◽

Sensible Heat Flux ◽

Dry Season ◽

Energy Balance Closure ◽

Net Radiation ◽

Wet Season

Abstract. Flux towers provide essential terrestrial climate, water, and radiation budget information needed for environmental monitoring and evaluation of climate change impacts on ecosystems and society in general. They are also intended for calibration and validation of satellite-based Earth observation and monitoring efforts, such as assessment of evapotranspiration from land and vegetation surfaces using surface energy balance approaches. In this paper, 15 years of Skukuza eddy covariance data, i.e. from 2000 to 2014, were analysed for surface energy balance closure (EBC) and partitioning. The surface energy balance closure was evaluated using the ordinary least squares regression (OLS) of turbulent energy fluxes (sensible (H) and latent heat (LE)) against available energy (net radiation (Rn) less soil heat (G)), and the energy balance ratio (EBR). Partitioning of the surface energy during the wet and dry seasons was also investigated, as well as how it is affected by atmospheric vapour pressure deficit (VPD), and net radiation. After filtering years with low-quality data (2004–2008), our results show an overall mean EBR of 0.93. Seasonal variations of EBR also showed the wet season with 1.17 and spring (1.02) being closest to unity, with the dry season (0.70) having the highest imbalance. Nocturnal surface energy closure was very low at 0.26, and this was linked to low friction velocity during night-time, with results showing an increase in closure with increase in friction velocity. The energy partition analysis showed that sensible heat flux is the dominant portion of net radiation, especially between March and October, followed by latent heat flux, and lastly the soil heat flux, and during the wet season where latent heat flux dominated sensible heat flux. An increase in net radiation was characterized by an increase in both LE and H, with LE showing a higher rate of increase than H in the wet season, and the reverse happening during the dry season. An increase in VPD is correlated with a decrease in LE and increase in H during the wet season, and an increase in both fluxes during the dry season.

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Updated cloud physics in a regional atmospheric climate model improves the modelled surface energy balance of Antarctica

The Cryosphere ◽

10.5194/tc-8-125-2014 ◽

2014 ◽

Vol 8 (1) ◽

pp. 125-135 ◽

Cited By ~ 44

Author(s):

J. M. van Wessem ◽

C. H. Reijmer ◽

J. T. M. Lenaerts ◽

W. J. van de Berg ◽

M. R. van den Broeke ◽

...

Keyword(s):

Heat Flux ◽

Energy Balance ◽

Surface Energy ◽

Surface Energy Balance ◽

Climate Model ◽

Sensible Heat Flux ◽

Sensible Heat ◽

Ice Cloud ◽

Long Wave ◽

Regional Atmospheric Climate Model

Abstract. In this study the effects of changes in the physics package of the regional atmospheric climate model RACMO2 on the modelled surface energy balance, near-surface temperature and wind speed of Antarctica are presented. The physics package update primarily consists of an improved turbulent and radiative flux scheme and a revised cloud scheme that includes a parameterisation for ice cloud super-saturation. The ice cloud super-saturation has led to more moisture being transported onto the continent, resulting in more and optically thicker clouds and more downward long-wave radiation. Overall, the updated model better represents the surface energy balance, based on a comparison with >750 months of data from nine automatic weather stations located in East Antarctica. Especially the representation of the turbulent sensible heat flux and net long-wave radiative flux has improved with a decrease in biases of up to 40%. As a result, modelled surface temperatures have increased and the bias, when compared to 10 m snow temperatures from 64 ice-core observations, has decreased from −2.3 K to −1.3 K. The weaker surface temperature inversion consequently improves the representation of the sensible heat flux, whereas wind speed biases remain unchanged. However, significant model biases remain, partly because RACMO2 at a resolution of 27 km is unable to resolve steep topography.

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Diurnal and Seasonal Variations of Surface Energy and CO2 Fluxes over a Site in Western Tibetan Plateau

Atmosphere ◽

10.3390/atmos11030260 ◽

2020 ◽

Vol 11 (3) ◽

pp. 260 ◽

Cited By ~ 1

Author(s):

Xingbing Zhao ◽

Changwei Liu ◽

Nan Yang ◽

Yubin Li

Keyword(s):

Heat Flux ◽

Energy Balance ◽

Tibetan Plateau ◽

Surface Energy ◽

Seasonal Variations ◽

Surface Energy Balance ◽

Diurnal Variations ◽

Heat Fluxes ◽

Co2 Fluxes ◽

Western Tibetan Plateau

Land surface process observations in the western Tibet Plateau (TP) are limited because of the abominable natural conditions. During the field campaign of the Third Tibetan Plateau Atmospheric Scientific Experiment (TIPEX III), continuous measurements on the four radiation fluxes (downward/upward short/long-wave radiations), three heat fluxes (turbulent sensible/latent heat fluxes and soil heat flux) and also CO2 flux were collected from June 2015 through January 2017 at Shiquanhe (32.50° N, 80.08° E, 4279.3 m above sea level) in the western Tibetan Plateau. Diurnal and seasonal variation characteristics of these surface energy and CO2 fluxes were presented and analyzed in this study. Results show that (1) diurnal variations of the seven energy fluxes were found with different magnitudes, (2) seasonal variations appeared for the seven energy fluxes with their maxima in summer and minima in winter, (3) diurnal and seasonal variations of respiration caused by the biological and chemical processes within the soil were found, and absorption (release) of CO2 around 0.1 mg m−2 s−1 occurred at afternoon of summer (midnight of winter), but the absorption and release generally canceled out from a yearly perspective; and (4) the surface energy balance ratio went through both diurnal and seasonal cycles, and in summer months the slopes of the fitting curve were above 0.6, but in winter months they were around 0.5. Comparing the results of the Shiquanhe site with the central and eastern TP sites, it was found that (1) they all generally had similar seasonal and diurnal variations of the fluxes, (2) caused by the low rainfall quantity, latent heat flux at Shiquanhe (daily daytime mean always less than 90 W m−2) was distinctively smaller than at the central and eastern TP sites during the wet season (generally larger than 100 W m−2), and (3) affected by various factors, the residual energy was comparatively larger at Shiquanhe, which led to a small surface energy balance ratio.

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