Determination of Area-Averaged Water Vapour Fluxes with Large Aperture and Radio Wave Scintillometers over a Heterogeneous Surface – Flevoland Field Experiment

Meijninger, W.M.L.; Green, A. E.; Hartogensis, O.K.; Kohsiek, W.; Hoedjes, J.C.B.; Zuurbier, R. M.; Bruin, H.A.R. de

doi:10.1023/a:1019683616097

Cited by 108 publications

(96 citation statements)

References 36 publications

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“…The combination of a (near-infrared) LAS and a (94-GHz) microwave scintillometer (known as the two-wavelength method) makes it possible to determine the fluxes of sensible heat and latent heat directly at scales of several kilometres from the path-averaged structure parameter data (C n 2 ) applying similarity relationships (Meijninger et al 2002. A footprint analysis of the setup performed by Meijninger et al (2006) showed that more than 85% of the source area of the scintillometers represents farmland (for all wind directions).…”

Section: Scintillometer and Airborne Measurementsmentioning

confidence: 99%

Energy balance closure for the LITFASS-2003 experiment

Foken

Mauder

Liebethal

et al. 2009

Theor Appl Climatol

140

108

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In the first part, this paper synthesises the main results from a series of previous studies on the closure of the local energy balance at low-vegetation sites during the LITFASS-2003 experiment. A residual of up to 25% of the available energy has been found which cannot be fully explained either by the measurement uncertainty of the single components of the surface energy balance or by the length of the flux-averaging period. In the second part, secondary circulations due to heterogeneities in the surface characteristics (roughness, thermal and moisture properties) are discussed as a possible cause for the observed energy balance non-closure. This hypothesis seems to be supported from the fluxes derived from area-averaging measurement techniques (scintillometers, aircraft).

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Section: Scintillometer and Airborne Measurementsmentioning

confidence: 99%

Energy balance closure for the LITFASS-2003 experiment

Foken

Mauder

Liebethal

et al. 2009

Theor Appl Climatol

140

108

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“…A LAS can obtain the area-averaged sensible heat flux, and the area-averaged evapotranspiration (ET) can be derived from the energy balance equation if the surface available energy (the net radiation minus the soil heat flux) is known (Meijninger et al, 2002b). Because the path lengths of the scintillometer are comparable to the pixel size of satellite images and area-averaged surface fluxes are obtained, the scintillometer has broad applications (McAneney et al, 1995;Foken et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

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.

484

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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“…As a consequence, an optical large-aperture scintillometer (LAS) can be used to determine path-averaged values of C 2 T , and a microwave scintillometer (MWS) in combination with LAS can provide both C 2 T and C 2 q (e.g. Kohsiek and Herben 1983;Meijninger et al 2002aMeijninger et al , 2006Lüdi et al 2005). In order to determine the surface sensible and latent heat fluxes from the estimates of C 2 T and C 2 q , respectively, Monin-Obukhov similarity theory (MOST) is applied.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Surface Heterogeneity on the Structure Parameters of Temperature and Specific Humidity: A Large-Eddy Simulation Case Study for the LITFASS-2003 Experiment

Maronga

Hartogensis

Raasch

et al. 2014

Boundary-Layer Meteorol

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We conduct a high-resolution large-eddy simulation (LES) case study in order to investigate the effects of surface heterogeneity on the (local) structure parameters of potential temperature C 2 T and specific humidity C 2 q in the convective boundary layer (CBL). The kilometre-scale heterogeneous land-use distribution as observed during the LITFASS-2003 experiment was prescribed at the surface of the LES model in order to simulate a realistic CBL development from the early morning until early afternoon. The surface patches are irregularly distributed and represent different land-use types that exhibit different roughness conditions as well as near-surface fluxes of sensible and latent heat. In the analysis, particular attention is given to the Monin-Obukhov similarity theory (MOST) relationships and local free convection (LFC) scaling for structure parameters in the surface layer, relating C 2 T and C 2 q to the surface fluxes of sensible and latent heat, respectively. Moreover we study possible effects of surface heterogeneity on scintillometer measurements that are usually performed in the surface layer. The LES data show that the local structure parameters reflect the surface heterogeneity pattern up to heights of 100-200 m. The assumption of a blending height, i.e. the height above the surface where the surface heterogeneity pattern is no longer visible in the structure parameters, is studied by means of a two-dimensional correlation analysis. We show that no such blending height is found at typical heights of scintillometer measurements for the studied case. Moreover, C 2 q does not follow MOST, which is ascribed to the entrainment of dry air at the top of the boundary layer. The application of MOST and LFC scaling to elevated C 2 T data still gives reliable estimates of the surface sensible heat flux. We show, however, that this flux, derived from scintillometer data, is only representative of the footprint area of the scintillometer, whose size depends strongly on the synoptic conditions.

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Determination of Area-Averaged Water Vapour Fluxes with Large Aperture and Radio Wave Scintillometers over a Heterogeneous Surface – Flevoland Field Experiment

Cited by 108 publications

References 36 publications

Energy balance closure for the LITFASS-2003 experiment

Energy balance closure for the LITFASS-2003 experiment

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

The Effect of Surface Heterogeneity on the Structure Parameters of Temperature and Specific Humidity: A Large-Eddy Simulation Case Study for the LITFASS-2003 Experiment

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