Forest Evapotranspiration and Energy Flux Partitioning Based on Eddy Covariance Methods in an Arid Desert Region of Northwest China

In this study, the characteristics of energy flux partitioning and evapotranspiration of P. euphratica forests were examined in the extreme arid region of Northwest China. Energy balance closure of the ecosystem was approximately 72% (H + LE = 0.72 ∗ (Rn-G)+7.72, r2=0.79, n=12095), where Rn is the net radiation, G is the soil heat flux, H is the sensible heat flux, and LE is the latent heat flux. LE was the main term of energy consumption at annual time scale because of higher value in the growing season. The ratios of the latent (LE) and sensible (H) heat fluxes to net radiation were 0.47 and 0.28 throughout the year, respectively. Moreover, the yearly evapotranspiration of P. euphratica forests was 744 mm year−1. And the mean daily ET was 5.09 mm·d−1 in the vibrant growing season. In particular, a small spike in the actual evapotranspiration distribution occurred during the soil ablation period due to the higher temperature and sufficient soil moisture associated with soil thawing. This period is accompanied by a series of physical processes, such as moisture transfer and heat exchange.

Download Full-text

Fetch Effect on Flux-Variance Estimations of Sensible and Latent Heat Fluxes of Camellia Sinensis

Atmosphere ◽

10.3390/atmos10060299 ◽

2019 ◽

Vol 10 (6) ◽

pp. 299

Author(s):

Noman Ali Buttar ◽

Hu Yongguang ◽

Josef Tanny ◽

M Waqar Akram ◽

Abdul Shabbir

Keyword(s):

Heat Flux ◽

Eddy Covariance ◽

Latent Heat ◽

Sensible Heat Flux ◽

Soil Heat Flux ◽

Surface Fluxes ◽

Heat Fluxes ◽

Effect Of Temperature ◽

Sensible Heat ◽

Fine Wire

Precise estimation of surface-atmosphere exchange is a major challenge in micrometeorology. Previous literature presented the eddy covariance (EC) as the most reliable method for the measurements of such fluxes. Nevertheless, the EC technique is quite expensive and complex, hence other simpler methods are sought. One of these methods is Flux-Variance (FV). The FV method estimates sensible heat flux (H) using high frequency (~10Hz) air temperature measurements by a fine wire thermocouple. Additional measurements of net radiation (Rn) and soil heat flux (G) allow the derivation of latent heat flux (LE) as the residual of the energy balance equation. In this study, the Flux Variance method was investigated, and the results were compared against eddy covariance measurements. The specific goal of the present study was to assess the performance of the FV method for the estimation of surface fluxes along a variable fetch. Experiment was carried out in a tea garden; an EC system measured latent and sensible heat fluxes and five fine-wire thermocouples were installed towards the wind dominant direction at different distances (fetch) of TC1 = 170 m, TC2 = 165 m, TC3 = 160 m, TC4 = 155 m and TC5 = 150 m from the field edge. Footprint analysis was employed to examine the effect of temperature measurement position on the ratio between 90% footprint and measurement height. Results showed a good agreement between FV and EC measurements of sensible heat flux, with all regression coefficients (R2) larger than 0.6; the sensor at 170 m (TC1), nearest to the EC system, had highest R2 = 0.86 and lowest root mean square error (RMSE = 25 Wm−2). The estimation of LE at TC1 was also in best agreement with eddy covariance, with the highest R2 = 0.90. The FV similarity constant varied along the fetch within the range 2.2–2.4.

Download Full-text

DYNAMICS OF HEAT FLUXES BY BOWEN AND MATMNXFLX AND NOAH FLDAS PRODUCTS IN THE PANTANAL OF MATO GROSSO.

Raega - O Espaço Geográfico em Análise ◽

10.5380/raega.v46i3.66981 ◽

2019 ◽

Vol 46 (3) ◽

pp. 07

Author(s):

Leilane Gomes Duarte ◽

Kelly Souza Romera ◽

Marlus Sabino ◽

Leone Francisco Amorim Curado ◽

Rafael Da Silva Palácios ◽

...

Keyword(s):

Heat Flux ◽

Latent Heat ◽

Sensible Heat Flux ◽

Bowen Ratio ◽

Absolute Error ◽

Soil Heat Flux ◽

Heat Fluxes ◽

Sensible Heat ◽

Seasonal Behavior ◽

Mato Grosso

This paper aimed to analyze the dynamics of the energy budget components: latent heat flux (LE), sensible heat flux (H) and soil heat flux (G), in the Mato Grosso Pantanal. The estimates of LE, H, and G were obtained by the Bowen ratio methods, using data from the micrometeorological tower located in the Baía das Pedras Park of SESC-Pantanal Ecological Resort, for the years 2011 to 2013. The normality of the variables Rn, LE, H and G, were tested by Kolmogorov-Smirnov test at 5% significance, and the seasonal differences of the fluxes were verified by the KruskalWallis test, α = 0.05. LE and H data from the remote sensing products MATMNXFLX and FLDAS_NOAH of the MERRA model was also acquired, and their comparison with the tower data was performed by the statistics of Spearman correlation (r), Mean Absolute Error (MAE), Root Mean Squared Erro (RMSE), bias, and Willmott's Concordance Index (d). It was observed that most of the available energy is used for evapotranspiration (latent heat), followed by sensible heat and soil heat flux. In the rainy season there is an increase in the partition of LE and G and reduction of H. Only the estimates of LE of MATMNXFLX and FLDAS_NOAH products correlate with the data observed in the meteorological tower. It is concluded that the energy partitions have a seasonal behavior and that the MATMNXFLX and FLDAS_NOAH products, after being calibrated, can be used to estimate LE in the Mato Grosso Pantanal.

Download Full-text

Sensible and latent heat flux from radiometric surface temperatures at the regional scale: methodology and validation

Biogeosciences Discussions ◽

10.5194/bgd-6-1945-2009 ◽

2009 ◽

Vol 6 (1) ◽

pp. 1945-1978 ◽

Cited By ~ 2

Author(s):

F. Miglietta ◽

B. Gioli ◽

Y. Brunet ◽

R. W. A. Hutjes ◽

A. Matese ◽

...

Keyword(s):

Heat Flux ◽

Eddy Covariance ◽

Latent Heat ◽

Latent Heat Flux ◽

Regional Scale ◽

Sensible Heat Flux ◽

Weather Conditions ◽

Heat Fluxes ◽

Net Radiation ◽

Surface Temperatures

Abstract. The CarboEurope Regional Experiment Strategy (CERES) was designed to develop and test a range of methodologies to assess regional surface energy and mass exchange of a large study area in the south-western part of France. This paper describes a methodology to estimate sensible and latent heat fluxes on the basis of net radiation, surface radiometric temperature measurements and information obtained from available products derived from the Meteosat Second Generation (MSG) geostationary meteorological satellite, weather stations and ground-based eddy covariance towers. It is based on a simplified bulk formulation of sensible heat flux that considers the degree of coupling between the vegetation and the atmosphere and estimates latent heat as the residual term of net radiation. Estimates of regional energy fluxes obtained in this way are validated at the regional scale by means of a comparison with direct flux measurements made by airborne eddy-covariance. The results show an overall good matching between airborne fluxes and estimates of sensible and latent heat flux obtained from radiometric surface temperatures that holds for different weather conditions and different land use types. The overall applicability of the proposed methodology to regional studies is discussed.

Download Full-text

Microclimatic comparison of lichen heaths and shrubs: shrubification generates atmospheric heating but subsurface cooling during the growing season

Biogeosciences ◽

10.5194/bg-18-1577-2021 ◽

2021 ◽

Vol 18 (5) ◽

pp. 1577-1599

Author(s):

Peter Aartsma ◽

Johan Asplund ◽

Arvid Odland ◽

Stefanie Reinhardt ◽

Hans Renssen

Keyword(s):

Heat Flux ◽

Soil Temperature ◽

Longwave Radiation ◽

Growing Season ◽

Soil Heat Flux ◽

Net Radiation ◽

Mountain Area ◽

Atmospheric Heating ◽

Air Temperatures ◽

The Difference

Abstract. Lichen heaths are declining in abundance in alpine and Arctic areas partly due to an increasing competition with shrubs. This shift in vegetation types might have important consequences for the microclimate and climate on a larger scale. The aim of our study is to measure the difference in microclimatic conditions between lichen heaths and shrub vegetation during the growing season. With a paired plot design, we measured the net radiation, soil heat flux, soil temperature and soil moisture on an alpine mountain area in southern Norway during the summer of 2018 and 2019. We determined that the daily net radiation of lichens was on average 3.15 MJ (26 %) lower than for shrubs during the growing season. This was mainly due to a higher albedo of the lichen heaths but also due to a larger longwave radiation loss. Subsequently, we estimate that a shift from a lichen heath to shrub vegetation leads to an average increase in atmospheric heating of 3.35 MJ d−1 during the growing season. Surprisingly, the soil heat flux and soil temperature were higher below lichens than below shrubs during days with high air temperatures. This implies that the relatively high albedo of lichens does not lead to a cooler soil compared to shrubs during the growing season. We predict that the thicker litter layer, the presence of soil shading and a higher evapotranspiration rate at shrub vegetation are far more important factors in explaining the variation in soil temperature between lichens and shrubs. Our study shows that a shift from lichen heaths to shrub vegetation in alpine and Arctic areas will lead to atmospheric heating, but it has a cooling effect on the subsurface during the growing season, especially when air temperatures are relatively high.

Download Full-text

Energy balance at the land-surface interface

MAUSAM ◽

10.54302/mausam.v47i2.3700 ◽

2021 ◽

Vol 47 (2) ◽

pp. 115-124

Author(s):

SANGEETA SAXENA ◽

J. S. PILLAI ◽

B. S. MURTHY ◽

K. G. VERNEKAR

Keyword(s):

Heat Flux ◽

Energy Balance ◽

Energy Budget ◽

Land Surface ◽

Sensible Heat Flux ◽

Bare Soil ◽

Soil Heat Flux ◽

Tropical Meteorology ◽

Small Scale ◽

Net Radiation

A small scale field experiment was conducted at the Indian Institute of Tropical Meteorology (IITM). Pashan Pune and the energy budget at the land surface interface was studied for clear and cloudy days over bare soil. Using instrumented towers, a net radiometer and soil temperature probe all the components of the energy budget. i.e. the sensible heat flux, latent heat flux, soil heat flux and net radiation were measured directly and the energy balance was computed. It is observed that when considered over the whole day, the energy budget is fairly balanced. As a part of energy budget, the Bowen's ratio is also discussed.

Download Full-text

The decline of alpine lichen heaths generates atmospheric heating but subsurface cooling during the growing season

10.5194/bg-2020-407 ◽

2020 ◽

Author(s):

Peter Aartsma ◽

Johan Asplund ◽

Arvid Odland ◽

Stefanie Reinhardt ◽

Hans Renssen

Keyword(s):

Heat Flux ◽

Soil Temperature ◽

Longwave Radiation ◽

Growing Season ◽

Soil Heat Flux ◽

Net Radiation ◽

Mountain Area ◽

Atmospheric Heating ◽

Air Temperatures ◽

The Difference

Abstract. Lichen heaths are declining in abundance in alpine and arctic areas partly due to an increasing competition with shrubs. This shift in vegetation types might have important consequences for the microclimate and climate on a larger scale. The aim of our study is to measure the difference in microclimatic conditions between lichen heaths and shrub vegetation during the growing season. With a paired plot design, we measured the net radiation, soil heat flux, soil temperature, and soil moisture on an alpine mountain area in south Norway during the summer of 2018 and 2019. We determined that the daily net radiation of lichens was on average 3.15 MJ (26 %) lower than for shrubs during the growing season. This was mainly due to a higher albedo of the lichen heaths, but also due to a larger longwave radiation loss. Subsequently, we estimate that a shift from a lichen heath to shrub vegetation leads to an average increase in atmospheric heating of 3.35 MJ per day during the growing season. Surprisingly, the soil heat flux and soil temperature were higher below lichens than below shrubs during days with high air temperatures. This implies that the relatively high albedo of lichens does not lead to a cooler soil compared to shrubs during the growing season. We hypothesize that the thicker litter layer, the presence of soil shading, and a higher evapotranspiration rate at shrub vegetation are far more important factors in explaining the variation in soil temperature between lichens and shrubs. Our study shows that a shift from lichen heaths to shrub vegetation in alpine and arctic areas will lead to atmospheric heating, but has a cooling effect on the subsurface during the growing season, especially when air temperatures are relatively high.

Download Full-text

A database of water and heat observations over grassland in the north-east of Japan

Earth System Science Data ◽

10.5194/essd-10-2295-2018 ◽

2018 ◽

Vol 10 (4) ◽

pp. 2295-2309 ◽

Cited By ~ 2

Author(s):

Wenchao Ma ◽

Jun Asanuma ◽

Jianqing Xu ◽

Yuichi Onda

Keyword(s):

Heat Flux ◽

Time Series ◽

Wind Speed ◽

Sensible Heat Flux ◽

Soil Heat Flux ◽

Shortwave Radiation ◽

Sensible Heat ◽

Net Radiation ◽

North East ◽

The North

Abstract. A highly valuable database of long-term hydrometeorological measurements is presented, containing in situ observations for a period of 37 years from a well-maintained grassland in the north-east of Japan. The observations include shortwave radiation, net radiation, air and dew point temperatures at three elevations, soil temperature at four depths, sensible heat flux, soil heat flux, wind speed, relative humidity, air pressure and precipitation. The heights of measurements are 1.6, 12.5 and 29.5 m above ground, with the soil-layer observations at depths of 0.02, 0.1, 0.5 and 1 m. This high-quality database includes four temporal resolutions of 10 s, 0.5 h, 1 h and 24 h, with the hourly data presented here. Monthly and annual statistics are presented at the database web page of the Center for Research in Isotopes and Environmental Dynamics and Prediction of the University of Tsukuba, http://doi.org/10.24575/0001.198108. We validated the data by comparing them with published data from the local meteorological agency in Tateno operated by the Japan Metrological Agency, including the average, maximum and minimum values of air temperature, shortwave radiation, wind speed, relative humidity and precipitation. We have generated a daily downward longwave radiation time series with a method developed by Kondo and Xu (1997) based on the observations from the database. This constructed time series agrees well with observations collected between 2002 and 2006, as evaluated based on the values of the Nash–Sutcliffe efficiency (=0.947) and percent bias (=1.486). For the whole database, annually averaged values show a positive trend in precipitation, air temperature, shortwave radiation, net radiation and sensible heat flux over the past 37 years, with a negative trend detected for wind speed, soil heat flux and soil temperature.

Download Full-text

Evaluation of the Soil, Vegetation, and Snow (SVS) Land Surface Model for the Simulation of Surface Energy Fluxes and Soil Moisture under Snow-Free Conditions

Atmosphere ◽

10.3390/atmos11030278 ◽

2020 ◽

Vol 11 (3) ◽

pp. 278 ◽

Cited By ~ 2

Author(s):

Gonzalo Leonardini ◽

François Anctil ◽

Maria Abrahamowicz ◽

Étienne Gaborit ◽

Vincent Vionnet ◽

...

Keyword(s):

Heat Flux ◽

Soil Moisture ◽

Land Surface ◽

Sensible Heat Flux ◽

Land Surface Model ◽

Soil Heat Flux ◽

Heat Fluxes ◽

Surface Model ◽

Point Scale ◽

Energy Fluxes

The recently developed Soil, Vegetation, and Snow (SVS) land surface model is being progressively implemented at Environment and Climate Change Canada (ECCC) for operational numerical weather and hydrological predictions. The objective of this study is to evaluate the ability of SVS, in offline point-scale mode and under snow-free conditions, to simulate the surface heat fluxes and soil moisture when compared to flux tower observations and simulations from the Canadian Land Surface Scheme (CLASS), used here as a benchmark model. To do this, we performed point-scale simulations of between 4 and 12 years of data records at six selected sites of the FLUXNET network under arid, Mediterranean and tropical climates. At all sites, SVS shows realistic simulations of latent heat flux, sensible heat flux and net radiation. Soil heat flux is reasonably well simulated for the arid sites and one Mediterranean site and poorly simulated for the tropical sites. On the other hand, surface soil moisture was reasonably well simulated at the arid and Mediterranean sites and poorly simulated at the tropical sites. SVS performance was comparable to CLASS not only for energy fluxes and soil moisture, but also for more specific processes such as evapotranspiration and water balance.

Download Full-text

IMPACTS OF SOYABEAN EXPANSION ON THE AMAZON ENERGY BALANCE: A CASE STUDY

Experimental Agriculture ◽

10.1017/s0014479711000391 ◽

2011 ◽

Vol 47 (3) ◽

pp. 553-567 ◽

Cited By ~ 8

Author(s):

PAULO JORGE DE OLIVEIRA PONTE DE SOUZA ◽

ARISTIDES RIBEIRO ◽

EDSON JOSÉ PAULINO DA ROCHA ◽

MARCEL DO NASCIMENTO BOTELHO ◽

ADRIANO MARLISOM LEÃO DE SOUSA ◽

...

Keyword(s):

Heat Flux ◽

Energy Balance ◽

Meteorological Data ◽

Sensible Heat Flux ◽

Bowen Ratio ◽

Growing Season ◽

Surface Conductance ◽

Net Radiation ◽

Growing Seasons

SUMMARYA micrometeorological experiment was carried out in an area of soyabean cultivation located in northeastern Para state, Brazil, in order to evaluate impacts on the local energy balance due to replacement of forests by soyabean. The meteorological data from forest ecosystems were collected in Caxiuanã forests located in central Para. The energy balance components were obtained using the Bowen ratio technique. Differences in energy balance components between ecosystems were significant during the soyabean growing season and more significant between growing seasons. During the soyabean growing season mean impacts of −15%, −9% and −27% on net radiation, latent heat flux (LE) and sensible heat flux (H), respectively, were observed. At specific soyabean stages, LE was higher than in the forest because of the high soyabean surface conductance of water vapour. However, during the production off-season the impacts were more significant (p < 0.05), showing a reduction of 78% in LE and a substantial increase in H (84%) because of the absence of vegetation cover over this period.

Download Full-text

Surface Temperature and Heat Fluxes: Comparison between Natural Forest and Oil Palm Plantation in Jambi Province Using Surface Energy Balance Algorithm for Land (SEBAL)

Agromet ◽

10.29244/j.agromet.33.2.62-70 ◽

2019 ◽

Vol 33 (2) ◽

pp. 62-70

Author(s):

Salis Deris Artikanur ◽

Tania June

Keyword(s):

Heat Flux ◽

Energy Balance ◽

Surface Temperature ◽

Oil Palm ◽

Surface Energy Balance ◽

Sensible Heat Flux ◽

Canopy Cover ◽

Heat Fluxes ◽

Net Radiation ◽

Oil Palm Plantation

One of the leading commodities that has contributed a lot of income for Indonesia is oil palm. Oil palm plantations in Jambi are widespread, affecting the energy balance and surface temperature. This study aims to compare surface temperature and heat fluxes of oil palm plantation with different ages, how is the difference between forest and oil palm plantation, and to analyze the effect of oil palm planting on micro-climate change in Jambi. Using the Surface Energy Balance Algorithm for Land (SEBAL), it was found that in Jambi, young oil palm (2 years old) had higher surface temperatures of 2oC compared with adult oil palm (19 years old). While the surface temperature of the adult oil palm plant is slightly higher than natural forest that is 0.5oC. The increase of the age of oil palm followed by the increase of plant height (h), Canopy Cover (CC), and surface roughness which resulted in the increase of NDVI value and the cooling effect around the plantation so that the surface temperature (Ts) decreased as indicated by equation TS = 27.00 - 0.1581h - 0.0317CC and NDVI = 0.1335 + 0.00892h + 0.00096CC. The sensible heat flux (H) is affected by surface temperature, roughness length, friction velocity, and aerodynamic resistance of the plant. The highest H value is in the oil palm plantation near Brimob which is 282 W/m2. Latent heat flux (LE) is the remainder of the net radiation minus the flux of the soil and the flux feels. The highest LE value is in the oil palm plantation of Pompa Air Village which is 710 W/m2. Substantially ground heat flux (G) is affected by net radiation, NDVI, surface temperature, and albedo. The highest value of G is in PT Pisifera Persada oil palm plantation of 98 W/m2.Keywords: NDVI, net radiation, sensible heat flux, latent heat flux, Canopy Cover

Download Full-text