Technical note: Using distributed temperature sensing for Bowen ratio evaporation measurements

Abstract. Rapid improvements in the precision and spatial resolution of distributed temperature sensing (DTS) technology now allow its use in hydrological and atmospheric sciences. Introduced by ) is the use of DTS for measuring the Bowen ratio (BR-DTS), to estimate the sensible and latent heat flux. The Bowen ratio is derived from DTS-measured vertical profiles of the air temperature and wet-bulb temperature. However, in previous research the measured temperatures were not validated, and the cables were not shielded from solar radiation. Additionally, the BR-DTS method has not been tested above a forest before, where temperature gradients are small and energy storage in the air column becomes important. In this paper the accuracy of the wet-bulb and air temperature measurements of the DTS are verified, and the resulting Bowen ratio and heat fluxes are compared to eddy covariance data. The performance of BR-DTS was tested on a 46 m high tower in a mixed forest in the centre of the Netherlands in August 2016. The average tree height is 26 to 30 m, and the temperatures are measured below, in, and above the canopy. Using the vertical temperature profiles the storage of latent and sensible heat in the air column was calculated. We found a significant effect of solar radiation on the temperature measurements, leading to a deviation of up to 3 K. By installing screens, the error caused by sunlight is reduced to under 1 K. Wind speed seems to have a minimal effect on the measured wet-bulb temperature, both below and above the canopy. After a simple quality control, the Bowen ratio measured by DTS correlates well with eddy covariance (EC) estimates (r2 = 0.59). The average energy balance closure between BR-DTS and EC is good, with a mean underestimation of 3.4 W m−2 by the BR-DTS method. However, during daytime the BR-DTS method overestimates the available energy, and during night-time the BR-DTS method estimates the available energy to be more negative. This difference could be related to the biomass heat storage, which is neglected in this study. The BR-DTS method overestimates the latent heat flux on average by 18.7 W m−2, with RMSE = 90 W m−2. The sensible heat flux is underestimated on average by 10.6 W m−2, with RMSE = 76 W m−2. Estimates of the BR-DTS can be improved once the uncertainties in the energy balance are reduced. However, applying, for example, Monin–Obukhov similarity theory could provide independent estimates for the sensible heat flux. This would make the determination of the highly uncertain and difficult to determine net available energy redundant.

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Technical note: using Distributed Temperature Sensing for Bowen ratio evaporation measurements

10.5194/hess-2017-446 ◽

2017 ◽

Author(s):

Bart Schilperoort ◽

Miriam Coenders-Gerrits ◽

Willem Luxemburg ◽

César Jiménez Rodríguez ◽

César Cisneros Vaca ◽

...

Keyword(s):

Heat Flux ◽

Energy Balance ◽

Solar Radiation ◽

Sensible Heat Flux ◽

Bowen Ratio ◽

Temperature Sensing ◽

Sensible Heat ◽

Distributed Temperature Sensing ◽

Available Energy ◽

Air Column

Abstract. Rapid improvements in the precision and spatial resolution of Distributed Temperature Sensing (DTS) technology now allows its use in hydrological and atmospheric sciences. Introduced by Euser [Hydrol. Earth Syst. Sci., 18, 2021–2032 (2014)] is the use of DTS for measuring the Bowen ratio (BR-DTS), to estimate the sensible and latent heat flux. The Bowen ratio is derived from DTS measured vertical profiles of the air temperature and wet-bulb temperature. However, in previous research the measured temperatures were not validated, and the cables were not shielded from solar radiation. Additionally, the BR-DTS method has not been tested above a forest before, where temperature gradients are small and energy storage in the air column becomes important. In this paper the accuracy of the wet-bulb and air temperature measurements of the DTS are verified, and the resulting Bowen ratio and heat fluxes are compared to eddy covariance data. The performance of BR-DTS was tested on a 46 m high tower in a mixed forest in the centre of the Netherlands in August 2016. The average tree height is 26 to 30 m, and the temperatures are measured below, in, and above the canopy. Using the vertical temperature profiles the storage of latent and sensible heat in the air column was calculated. We found a significant effect of solar radiation on the temperature measurements, leading to a deviation of up to 3 K. By installing screens, the error caused by sunlight is reduced to under 1 K. Wind speed seems to have a minimal effect on the measured wet-bulb temperature, both below and above the canopy. After a simple quality control, the Bowen ratio measured by DTS correlates well with eddy covariance (EC) estimates (r2 = 0.59). The average energy balance closure between BR-DTS and EC is good, with a mean underestimation of 3.4 W m−2 by the BR-DTS method. However, during daytime the BR-DTS method overestimates the available energy, and during night-time the BR-DTS method estimates the available energy to be more negative. This difference could be related to the biomass heat storage, which is neglected in this study. The BR-DTS method overestimates the latent heat flux on average by 18.7 W m−2, with RMSE = 90 W m−2. The sensible heat flux is underestimated on average by 10.6 W m−2, with RMSE = 76 W m−2. Estimates of the BR-DTS can be improved once the uncertainties in the energy balance are reduced. However, applying e.g. Monin-Obukhov similarity theory could provide independent estimates for the sensible heat flux. This would make the determination of the highly uncertain and difficult to determine net available energy redundant.

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Diurnal Energy Balance in a Mango Orchard in the Northeast of Pará, Brazil

Revista Brasileira de Meteorologia ◽

10.1590/0102-7786333012 ◽

2018 ◽

Vol 33 (3) ◽

pp. 537-546 ◽

Cited By ~ 1

Author(s):

Paulo Jorge de Oliveira Ponte de Souza ◽

Juliana Chagas Rodrigues ◽

Adriano Marlisom Leão de Sousa ◽

Everaldo Barreiros de Souza

Keyword(s):

Heat Flux ◽

Energy Balance ◽

Latent Heat ◽

Latent Heat Flux ◽

Soil Cover ◽

Sensible Heat Flux ◽

Sensible Heat ◽

Net Radiation ◽

Growing Seasons ◽

Available Energy

Abstract This study aimed to evaluate the diurnal energy balance during the reproductive stage of two growing seasons of a mango orchard in the northeast of Pará, Brazil. Therefore, a micrometeorological tower was installed and instrumented, in the center of the experimental area, to monitor meteorological variables, besides the phenological evaluation of the mango orchard, which was carried out during growing seasons of 2010-2011 (October 2010 to January 2011) and of 2011-2012 (September 2011 to January 2012). The energy balance was obtained by the bowen ration technique, and the available energy partitioned into heat flux to the ground, sensible heat and latent heat. The amount of rainfall was crucial to the partition of the net radiation in the energy balance components. It provided the variation in the consumption of available energy between 69% and 78% as latent heat flux, and between 23% and 32% as sensible heat flux. The heat flux to the ground was small, representing less than 1% of the net radiation, showing that the mango orchard exhibits good soil cover preventing large variations in soil heating.

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Study of energy balance components at different growth stages of green gram grown in new alluvial zone of West Bengal

MAUSAM ◽

10.54302/mausam.v71i2.29 ◽

2021 ◽

Vol 71 (2) ◽

pp. 315-320

Author(s):

MONDAL SOUMEN ◽

BANERJEE SAON ◽

CHAKRABORTY SHAON ◽

SAHA SALIL ◽

MUKHERJEE ASIS

Keyword(s):

Heat Flux ◽

Energy Balance ◽

West Bengal ◽

Sensible Heat Flux ◽

Bowen Ratio ◽

Green Gram ◽

Growth Stages ◽

Sensible Heat ◽

Net Radiation ◽

Ground Heat Flux

An experiment was conducted in the experimental farm of Bidhan Chandra KrishiViswavidyalaya, Nadia, West Bengal to study the radiation pattern and its balance over green gram (Vignaradiata var. Samrat). The BREB method was used to determine the sensible heat flux and latent energy. The net radiation was measured through net radiometer and the ground heat flux was measured using Fourier's law. Both the diurnal and seasonal variation of net radiation were studied. Similarly, the energy balance components were studied regularly for different crop growth stages as well as on diurnal basis. It is observed that the net radiation varies from 6.32 Wm-2 to 606.43 Wm-2. The latent heat flux constitutes more than 50% of the net radiation for all growth stages as depicted by energy balance partitioning. The sensible heat flux is partitioned into 10% to 20% of total net radiation throughout the growth stages of green gram, which is the lowest in magnitude among all three energy fluxes. The relationship between Bowen ratio and Vapour pressure deficit (VPD), Bowen ratio and Canopy air temperature difference (CATD) was studied. It was found that Bowen ratio is negatively correlated with VPD but positively correlated with CATD. This study enables to monitor ET pattern through latent heat flux and microclimatic characteristics through sensible and ground heat flux.

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Bowen ratio determination of sensible and latent heat fluxes in a humid tropical environment at Ile- Ife, Nigeria

MAUSAM ◽

10.54302/mausam.v52i4.1739 ◽

2022 ◽

Vol 52 (4) ◽

pp. 669-678

Author(s):

O. O. JEGEDE ◽

Th. FOKEN ◽

A. A. BALOGUN ◽

O. J. ABIMBOLA

Keyword(s):

Heat Flux ◽

Energy Balance ◽

Latent Heat ◽

Sensible Heat Flux ◽

Bowen Ratio ◽

Heat Fluxes ◽

Sensible Heat ◽

Night Time ◽

Forest Zone ◽

Surface Conditions

The Bowen ratio energy balance (BREB) method is the most widely used for estimating the fluxes of sensible heat and latent heat near the surface largely because of its conceptual simplicity and the robustness of instrumentation required. We have adopted the same technique here to study partitioning of measured available energy (difference of net radiation and soil heat flux) over bare soil at a humid tropical location in Ile-Ife, Nigeria (7° 33' N, 4° 34' E) between 7 and 10 March, 1999. Results obtained of the diurnal variations of the both fluxes in relation to the changing surface conditions (case studies) are quite satisfactory. For dry days, the sensible heat flux is comparatively of the same magnitude as the latent heat flux but it is less, about 10-60% for the wet surface conditions. It is clear from the present study that for the tropical forest zone, evaporation is the next important factor after radiation in the energy balance due to the humid conditions that usually prevail. Except for the few instances when very weak gradients exist, particularly of moisture, during transition periods (at sunrise or sunset), the technique has worked satisfactorily for day as well as night time periods regardless of prevailing weather conditions.

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Response of the Energy Balance on the Margin of the Greenland Ice Sheet to Temperature Changes

Journal of Glaciology ◽

10.1017/s0022143000009461 ◽

1990 ◽

Vol 36 (123) ◽

pp. 217-221 ◽

Cited By ~ 25

Author(s):

Roger J. Braithwaite ◽

Ole B. Olesen

Keyword(s):

Heat Flux ◽

Energy Balance ◽

Air Temperature ◽

Sensible Heat Flux ◽

Ice Sheet ◽

Temperature Response ◽

Greenland Ice Sheet ◽

Energy Balance Model ◽

Balance Model ◽

Sensible Heat

AbstractDaily ice ablation on two outlet glaciers from the Greenland ice sheet, Nordbogletscher (1979–83) and Qamanârssûp sermia (1980–86), is related to air temperature by a linear regression equation. Analysis of this ablation-temperature equation with the help of a simple energy-balance model shows that sensible-heat flux has the greatest temperature response and accounts for about one-half of the temperature response of ablation. Net radiation accounts for about one-quarter of the temperature response of ablation, and latent-heat flux and errors account for the remainder. The temperature response of sensible-heat flux at QQamanârssûp sermia is greater than at Nordbogletscher mainly due to higher average wind speeds. The association of high winds with high temperatures during Föhn events further increases sensible-heat flux. The energy-balance model shows that ablation from a snow surface is only about half that from an ice surface at the same air temperature.

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Components of the energy balance of the ground surface and their effect on the thermics of the substrata of the vegetation oasis at Henryk Arctowski Station, King George Island, South Shetland Islands

Polar Record ◽

10.1017/s003224740001593x ◽

2000 ◽

Vol 36 (196) ◽

pp. 3-18 ◽

Cited By ~ 1

Author(s):

P. Prosek ◽

M. Janouch ◽

K. Láska

Keyword(s):

Heat Flux ◽

Energy Balance ◽

Soil Temperature ◽

Sensible Heat Flux ◽

Ground Surface ◽

South Shetland Islands ◽

Radiation Balance ◽

Sensible Heat ◽

King George Island ◽

Shetland Islands

AbstractThis article presents the results of measurements of the components of ground-surface energy balance (radiation balance, sensible heat flux, latent heat flux, and ground heat flux) taken during the 1994/95 summer season at Poland's Henryk Arctowski Station, King George Island, South Shetland Islands (62°09'42”S, 58°28'10”W). This was the first time that these complex measurements had been taken in the central part of the South Shetlands archipelago. The results are evaluated at the level of daily and seasonal fluctuations. The consequences of energy balance on the temperature conditions of the soil substrata are highlighted. The verification of the degree of influence of a subset of energy-balance components on soil temperature allowed analysis of the relationships among soil temperature, radiation balance, and sensible heat flux. This analysis leads to the conclusion that there is a rapid reaction of the soil temperature to the radiation balance and sensible heat flux to a depth of 5 cm. The boundary atmosphere and soil substrate represent the basic components of the ecotops of the Antarctic vegetation oasis, so these results are interpreted in pedological or botanical studies in the search for environmental influences on the vegetation.

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The impact of broadleaved woodland on water resources in lowland UK: II. Evaporation estimates from sensible heat flux measurements over beech woodland and grass on chalk sites in Hampshire

Hydrology and Earth System Sciences ◽

10.5194/hess-9-607-2005 ◽

2005 ◽

Vol 9 (6) ◽

pp. 607-613 ◽

Cited By ~ 12

Author(s):

J. Roberts ◽

P. Rosier ◽

D. M. Smith

Keyword(s):

Heat Flux ◽

Energy Balance ◽

Excellent Agreement ◽

Sensible Heat Flux ◽

Late Summer ◽

Eddy Correlation ◽

Sensible Heat ◽

Flux Measurements ◽

Shallow Soils ◽

The Impact

Abstract. The impact on recharge to the Chalk aquifer of substitution of broadleaved woodland for pasture is a matter of concern in the UK. Hence, measurements of energy balance components were made above beech woodland and above pasture, both growing on shallow soils over chalk in Hampshire. Latent heat flux (evaporation) was calculated as the residual from these measurements of energy balances in which sensible heat flux was measured with an eddy correlation instrument that determined fast response vertical wind speeds and associated temperature changes. Assessment of wind turbulence statistics confirmed that the eddy correlation device performed satisfactorily in both wet and dry conditions. There was excellent agreement between forest transpiration measurements made by eddy correlation and stand level tree transpiration measured with sap flow devices. Over the period of the measurements, from March 1999 to late summer 2000, changes in soil water content were small and grassland evaporation and transpiration estimated from energy balance-eddy flux measurements were in excellent agreement with Penman estimates of potential evaporation. Over the 18-month measurement period, the cumulative difference between broadleaved woodland and grassland was small but evaporation from the grassland was 3% higher than that from the woodland. In the springs of 1999 and 2000, evaporation from the grassland was greater than that from the woodland. However, following leaf emergence in the woodland, the difference in cumulative evaporation diminished until the following spring.

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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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Energy Balance Calculations for the Ablation Period 1982 at Vernagtferner. Oetztal Alps

Annals of Glaciology ◽

10.3189/1985aog6-1-158-160 ◽

1985 ◽

Vol 6 ◽

pp. 158-160 ◽

Cited By ~ 7

Author(s):

Heidi Escher-Vetter

Keyword(s):

Heat Flux ◽

Energy Balance ◽

Air Temperature ◽

Sensible Heat Flux ◽

Longwave Radiation ◽

Radiation Balance ◽

Sensible Heat ◽

The Individual ◽

The Relationship ◽

Climatic Pattern

In this paper, some features of energy balance terms will be discussed in respect to the melting capacity available at the surface of Vernagtferner in the Oetztal Alps. The climatic pattern of summer 1982 is described, then the method of calculating individual terms (shortwave and longwave radiation balance, sensible and latent heat flux) from records of radiation, air temperature, humidity and wind. The results of these calculations are discussed for ice, firn and snow areas of the glacier. In particular the relationship between the four terms is shown for 15 July 1982, the day with highest meltwater production in 1982. These values are then compared with the maximum values of the individual terms, showing that the highest meltwater production is caused by the combination of quite high values of the individual terms, but not of the absolutely highest ones. The importance of sensible heat flux for meltwater production in 1982 is discussed: comparison between meltwater production for the whole summer and measured runoff shows reasonable accordance.

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