Oxygen Sensitivity of Krypton and Lyman-<i>α</i>Hygrometers

Dijk, Arjan van; Kohsiek, W.; Bruin, H.A.R. de

doi:10.1175/1520-0426(2003)020<0143:osokal>2.0.co;2

Cited by 65 publications

(34 citation statements)

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“…Van Dijk et al (2003) have shown that k o depends on the pathlength of the krypton hygrometer. Their Table 2 provides the value of 0.00034 m 3 g −1 mm −1 for the pathlength of 13 mm that was used during EBEX.…”

Section: Oxygen Correctionmentioning

confidence: 99%

The Energy Balance Experiment EBEX-2000. Part I: overview and energy balance

Oncley

Foken

Vogt

et al. 2007

Boundary-Layer Meteorol

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272

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An overview of the Energy Balance Experiment (EBEX-2000) is given. This experiment studied the ability of state-of-the-art measurements to close the surface energy balance over a surface (a vegetative canopy with large evapotranspiration) where closure has been difficult to obtain. A flood-irrigated cotton field over uniform terrain was used, though aerial imagery and direct flux measurements showed that the surface still was inhomogeneous. All major terms of the surface energy balance were measured at nine sites to characterize the spatial variability across the field. Included in these observations was an estimate of heat storage in the plant canopy. The resultant imbalance still was 10%, which exceeds the estimated measurement error. We speculate that horizontal advection in the layer between the canopy top and our flux measurement height may cause this imbalance, though our estimates of

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Section: Oxygen Correctionmentioning

confidence: 99%

The Energy Balance Experiment EBEX-2000. Part I: overview and energy balance

Oncley

Foken

Vogt

et al. 2007

Boundary-Layer Meteorol

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340

272

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“…LI-7500 gas analyser) compared to the sonic anemometer by the calculation and maximisation of cross correlations -Cross-wind correction of the sonic temperature according to Liu et al (2001), if not already implemented in sensor software (necessary for METEK USA-1) -Application of the planar fit method for coordinate rotation (Wilczak et al 2001) -Correction of oxygen cross sensitivity for Krypton hygrometers (Tanner et al 1993;van Dijk et al 2003) -Spectral corrections according to Moore (1986) using the spectral models by Kaimal et al (1972) and Højstrup (1981) except for the longitudinal separation which is accounted for by the maximisation of the covariances -Conversion of fluctuations of the sonic temperature into fluctuations of the actual temperature according to Schotanus et al (1983) -Density correction of scalar fluxes of H 2 O and CO 2 as suggested by Webb et al (1980) and Liebethal andFoken (2003, 2004) -Iteration of the correction steps due to their interdependence ) -Data quality analysis according to Foken and Wichura (1996) in the updated version by Foken et al (2004) An angle of attack correction (Nakai et al 2006;van der Molen et al 2004) was not made as used by Cava et al (2008), because this correction is usually determined in the wind tunnel for 'laminar flow' and overestimates the fluxes in the turbulent atmosphere (Högström and Smedman 2004). The effect of the different steps of data processing on the closure of the energy balance was discussed by Mauder and Foken (2006).…”

Section: Fluxes Of Sensible and Latent Heatmentioning

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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“…Then, the raw turbulence data were re-processed using the University of Bayreuth turbulence flux data processing software, Turbulenzknecht 2 (TK2; Foken et al 2004;Mauder and Foken 2004). The flux calculation correction procedures implemented in TK2 included (i) spike detection and rejection algorithms (Vickers and Mahrt 1997), (ii) coordinate rotation using the planar fit method (Wilczak et al 2001), (iii) double rotation for aligning the wind component u with the mean wind direction and setting the mean values of v and w to zero, (iv) Conversion of sonic virtual temperature to air temperature after Schotanus et al (1983), (v) correction of oxygen cross sensitivity for the Krypton hygrometer (Tanner et al 1993;Van Dijk et al 2003 ), (vi) correction for spectral loss after Moore (1986), (vii) density fluctuation corrections for water vapour (Webb et al 1980;Liebethal and Foken 2003), and (viii) tests of stationarity and integral turbulence characteristics . Following Foken and Wichura (1996), we subjected all flux data and calculated statistics to strict data limits to reject spurious values, and to quality-control flags based on integral turbulence characteristics; only data with quality flags 1-5 for fluxes and 1-3 for integral turbulence characteristics were used in the following analyses.…”

Section: Measurements and Data Analysismentioning

confidence: 99%

Surface Energy Balance Measurements Above an Exurban Residential Neighbourhood of Kansas City, Missouri

Balogun

Adegoke

Vezhapparambu

et al. 2009

Boundary-Layer Meteorol

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Previous measurements of urban energy balances generally have been limited to densely built, central city sites and older suburban locations with mature tree canopies that are higher than the height of the buildings. In contrast, few data are available for the extensive, open vegetated types typical of low-density residential areas that have been newly converted from rural land use. We made direct measurements of surface energy fluxes using the eddy-covariance technique at Greenwood, a recently developed exurban neighbourhood near Kansas City, Missouri, USA, during an intensive field campaign in August 2004. were 253 and 370 W m −2 , respectively for the cloudy and near clear-sky conditions, while mean daily values were 114 for cloudy and 171 W m −2 for near clear-sky conditions, respectively. Midday surface albedo values were 0.25 and 0.24 for the cloudy and near clear-sky conditions, respectively. The site exhibited an angular dependence on the solar elevation angle, in contrast to previous observations over urban and suburban areas, but similar to vegetated surfaces. The latent heat flux (Q E ), sensible heat flux (Q H ), and the residual heat storage Q s terms accounted for between 46-58%, 21-23%, and 18-31% of R n , respectively, for all-sky conditions and time averages. The observed albedo, R n , and Q E values are higher than the values that have been reported for suburban areas with high summer evapotranspiration rates in North America. These results suggest that the rapidly growing residential areas at the exurban fringe of large metropolitan areas have a surface energy balance that is more similar to the rural areas from which they were developed than it is to the older suburbs and city centres that make up the urban fabric to which they are being joined.

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Oxygen Sensitivity of Krypton and Lyman-αHygrometers

Cited by 65 publications

References 1 publication

The Energy Balance Experiment EBEX-2000. Part I: overview and energy balance

The Energy Balance Experiment EBEX-2000. Part I: overview and energy balance

Energy balance closure for the LITFASS-2003 experiment

Surface Energy Balance Measurements Above an Exurban Residential Neighbourhood of Kansas City, Missouri

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