EAGLE 2006 – Multi-purpose, multi-angle and multi-sensor in-situ and airborne campaigns over grassland and forest

Su, Zhongbo; Timmermans, W.; Tol, Christiaan van der; Dost, R.J.J.; Bianchi, R.; Gómez, J.; House, Alan; Hajnsek, Irena; Menenti, Massimo; Magliulo, Vincenzo; Esposito, Marco; Haarbrink, R.; Bosveld, F. C.; Rothe, Rasmus; Baltink, Henk Klein; Vekerdy, Z.; Sobrino, José A.; Timmermans, J.; Laake, P. van; Salama, Mhd. Suhyb; Kwast, H. van der; Claassen, E.; Stolk, A.; Li, Jia; Moors, E.J.; Hartogensis, O.K.; Gillespie, A. R.

doi:10.5194/hess-13-833-2009

Cited by 58 publications

(51 citation statements)

References 12 publications

(5 reference statements)

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“…Ezzahar et al (2007) have suggested that the differences between the two measurements could be explained by differences in terms of the source areas of the LAS and EC and the closure failure of the energy balance of the EC. Su et al (2009) have proposed that the difference between the two measurements may be attributed to the sensitivity of the H LAS to the aerodynamic roughness length Fig. 9, which reveals that the H EC and H LAS were much closer to each other, with only a 6% difference (R 2 = 0.67, n = 1202).…”

Section: Comparison Of the Sensible Heat Fluxes Derived From Las And Ecmentioning

confidence: 98%

A comparison of eddy-covariance and large aperture scintillometer measurements with respect to the energy balance closure problem

Liu

Wang

et al. 2011

Hydrol. Earth Syst. Sci.

476

275

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Abstract.We analyzed the seasonal variations of energy balance components over three different surfaces: irrigated cropland (Yingke, YK), alpine meadow (A'rou, AR), and spruce forest (Guantan, GT). The energy balance components were measured using eddy covariance (EC) systems and a large aperture scintillometer (LAS) in the Heihe River Basin, China, in 2008 and 2009. We also determined the source areas of the EC and LAS measurements with a footprint model for each site and discussed the differences between the sensible heat fluxes measured with EC and LAS at AR. The results show that the main EC source areas were within a radius of 250 m at all of the sites. The main source area for the LAS (with a path length of 2390 m) stretched along a path line approximately 2000 m long and 700 m wide. The surface characteristics in the source areas changed with the season at each site, and there were characteristic seasonal variations in the energy balance components at all of the sites. The sensible heat flux was the main term of the energy budget during the dormant season. During the growing season, however, the latent heat flux dominated the energy budget, and an obvious "oasis effect" was observed at YK. The sensible heat fluxes measured by LAS at AR were larger than those measured by EC at the same site. This difference seems to be caused by the so-called energy imbalance phenomenon, the heterogeneity of the underlying surfaces, and the difference between the source areas of the LAS and EC measurements.

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Section: Comparison Of the Sensible Heat Fluxes Derived From Las And Ecmentioning

confidence: 98%

A comparison of eddy-covariance and large aperture scintillometer measurements with respect to the energy balance closure problem

Liu

Wang

et al. 2011

Hydrol. Earth Syst. Sci.

476

275

View full text Add to dashboard Cite

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“…In addition, several airborne campaigns were performed to assess SSM retrieval over large areas: EuroSTARRS in France and Spain (Saleh et al, 2004), NAFE/CoSMOS in Australia (Panciera et al, 2008), EA-GLE2006 in Germany (Su et al, 2009), HOBE in Denmark (Bircher et al, 2012). These studies showed that the response of L-band brightness temperatures to SSM is affected by biomass conditions (Saleh et al, 2004).…”

mentioning

confidence: 99%

Spatial and temporal variability of biophysical variables in southwestern France from airborne L-band radiometry

Zakharova¹,

Calvet²,

Lafont³

et al. 2012

Hydrol. Earth Syst. Sci.

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“…The surrounding area is characterized by the presence of broadleaved and coniferous tree species, distributed in blocks around the tower site (Bosveld and Bouten, 2001). Within a 500 m radius it is possible to find native tree species such as beech (Fagus sylvatica L.), pedunculate oak (Quercus robur L.) and Scots pine (Pinus sylvestris L.), as well as the introduced species hemlock (Tsuga heterophylla (Rafinesque) Sargent) and Japanese larch (Larix kaempferi (Lambert) Carriére) (Erisman et al, 1998;Raj et al, 2014;Su et al, 2009;Bosveld and Bouten, 2001;Tietema et al, 2002;Van Wijk et al, 2000;Weligepolage et al, 2013). Canopy heights differ between cover types depending on species and growing stage.…”

Section: Study Sitementioning

confidence: 99%

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

Schilperoort

Coenders-Gerrits

Luxemburg

et al. 2018

Hydrol. Earth Syst. Sci.

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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 Euser et al. (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 (r 2 = 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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EAGLE 2006 – Multi-purpose, multi-angle and multi-sensor in-situ and airborne campaigns over grassland and forest

Cited by 58 publications

References 12 publications

A comparison of eddy-covariance and large aperture scintillometer measurements with respect to the energy balance closure problem

A comparison of eddy-covariance and large aperture scintillometer measurements with respect to the energy balance closure problem

Spatial and temporal variability of biophysical variables in southwestern France from airborne L-band radiometry

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

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