Sampling Bias on Cup Anemometer Mean Winds

Kristensen, Leif; Hansen, O.F.; Højstrup, Jørgen

doi:10.1002/we.85

Cited by 5 publications

(2 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…On the other hand, in the real atmosphere with fluctuating wind speed due to turbulence, cup anemometers show an "overspeeding" effect (i.e. their response to increasing wind speed is faster than to decreasing wind speed leading to an overestimation of the average value) at lower wind speeds (Rotach, 1991;Kristensen et al, 2003). The lowest measuring points carrying a large fraction of the horizontal fluxes are especially affected by this overestimation.…”

Section: Wind Speed Measurementsmentioning

confidence: 99%

Are ammonia emissions from field-applied slurry substantially over-estimated in European emission inventories?

et al. 2012

View full text Add to dashboard Cite

Abstract. The EMEP/EEA guidebook 2009 for agricultural emission inventories reports an average ammonia (NH3) emission factor (EF) by volatilisation of 55% of the applied total ammoniacal nitrogen (TAN) content for cattle slurry, and 35% losses for pig slurry, irrespective of the type of surface or slurry characteristics such as dry matter content and pH. In this review article, we compiled over 350 measurements of EFs published between 1991 and 2011. The standard slurry application technique during the early years of this period, when a large number of measurements were made, was spreading by splash plate, and as a result reference EFs given in many European inventories are predominantly based on this technique. However, slurry application practices have evolved since then, while there has also been a shift in measurement techniques and investigated plot sizes. We therefore classified the available measurements according to the flux measurement technique or measurement plot size and year of measurement. Medium size plots (usually circles between 20 to 50 m radius) generally yielded the highest EFs. The most commonly used measurement setups at this scale were based on the Integrated Horizontal Flux method (IHF or the ZINST method (a simplified IHF method)). Several empirical models were published in the years 1993 to 2003 predicting NH3 EFs as a function of meteorology and slurry characteristics (Menzi et al., 1998; Søgaard et al., 2002). More recent measurements show substantially lower EFs which calls for new measurement series in order to validate the various measurement approaches against each other and to derive revised inputs for inclusion into emission inventories.

show abstract

Section: Wind Speed Measurementsmentioning

confidence: 99%

Are ammonia emissions from field-applied slurry substantially over-estimated in European emission inventories?

et al. 2012

View full text Add to dashboard Cite

show abstract

“…The performances of this instrument have been 43 thoroughly studied since the XIX century (a quite complete review 44 of the literature on this wind sensor can be found in [2]). As a con- 45 sequence, different sources of error have been identified in relation 46 to cup anemometer wind speed measurements: turbulence [3][4][5][6], 47 non-linearity of the sensor performance [7,8], and the sampling 48 method [9]. Additionally, it should be underlined that uncertainties 49 associated to cup anemometer wind speed measurements have 50 been widely studied, as they are relevant for wind turbines perfor-51 mances [10][11][12].…”

mentioning

confidence: 99%