Environmental Instrumentation

Fritschen, Leo J.; Gay, Lloyd W.

doi:10.1007/978-1-4612-6205-3

Cited by 136 publications

(84 citation statements)

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“…The five anemometer heights are 28, 53, 118, 203 and 402 cm. We notice that the bottom height complies with the recommendation of Fritschen and Gay (1979), which stated that the anemometer height should be fivefold greater than the roughness length, Z 0 (i.e. 0.3 and 3 mm, respectively, in plots CT and RT, see Table 7) The two MGS are synchronized.…”

Section: Instrumentationsupporting

confidence: 78%

Profile of the horizontal wind variance near the ground in near neutral flow – K-theory and the transport of the turbulent kinetic energy

Yahaya

Frangi

2009

Ann. Geophys.

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Abstract. This paper deals with the characteristics of the atmospheric turbulent flow in the vicinity of the ground, and particularly with the profile of the horizontal wind variance. The study is based on experimental measurements performed with fast cup anemometers located near the ground at 5 different levels (from 0.25 to 4 m) and sampled at 1 Hz. The experiment was carried over two agricultural plots with various tillage treatments in a fallow semiarid area (Central Aragon, Spain). The results of this study reveal that near the ground surface and under moderate wind, the horizontal wind variance logarithmically increases with height, in direct relationship with the friction velocity and the roughness length scale. A theoretical development has allowed us to link this behaviour to the modeling of the turbulent kinetic energy (TKE) transport through the eddy diffusivity. Thus, the study proposes a formulation of the similarity universal function of the horizontal wind variance. Besides, the formulation offers a new method for the determination of the friction velocity and the roughness length scale and can be used for the evaluation of the TKE transport rate.

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Section: Instrumentationsupporting

confidence: 78%

Profile of the horizontal wind variance near the ground in near neutral flow – K-theory and the transport of the turbulent kinetic energy

Yahaya

Frangi

2009

Ann. Geophys.

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“…To estimate the correct detection limit from Eq. (2) we therefore use the general formula for the absolute error X (Fritschen and Gay, 1979) which is equivalent to the total differential of the function X consisting of several independent variables y i , each with its own absolute error y i X = y 1 ∂X ∂y 1 +…”

Section: Appendix Bmentioning

confidence: 99%

Eddy covariance methane measurements at a Ponderosa pine plantation in California

et al. 2009

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Abstract. Long term methane flux measurements have been mostly performed with plant or soil enclosure techniques on specific components of an ecosystem. New fast response methane analyzers make it possible to use the eddy covariance (EC) technique instead. The EC technique is advantageous because it allows continuous flux measurements integrating over a larger and more representative area including the complete ecosystem, and allows fluxes to be observed as environmental conditions change naturally without disturbance. We deployed the closed-path Fast Methane analyzer (FMA) from Los Gatos Research Ltd and demonstrate its performance for EC measurements at a Ponderosa pine plantation at the Blodgett Forest site in central California. The fluctuations of the CH 4 concentration measured at 10 Hz appear to be small and their standard deviation is comparable to the magnitude of the signal noise (±5 ppbv). Consequently, the power spectra typically have a white noise signature at the high frequency end (a slope of +1). Nevertheless, in the frequency range important for turbulent exchange, the cospectra of CH 4 compare very well with all other scalar cospectra confirming the quality of the FMA measurements are good for the EC technique. We furthermore evaluate the complications of combined open and closed-path measurements when applying the Webb-Pearman-Leuning (WPL) corrections (Webb et al., 1980) and the consequences of a phase lag between the water vapor and methane signal inside the closed path system. The results of diurnal variations of CH 4 concentrations and fluxes are summarized and compared to the monthly results of process-based model calculations.

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“…The soil heat flux was measured at depths of 20 and 30 mm by flux plates (TN0 transducer type WS 31-Cp). To obtain correct values for the soil heat flux at surface level (Oh) corrections were carried out for the heat capacity of the soil (Fritschen and Gay, 1979) and for the flux plate dimensions and the ratio of the tranducer's conductivity and soil conductivity according to Philip (1969).…”

Section: Methodsmentioning

confidence: 99%

Nighttime exchange processes near the soil surface of a maize canopy

Jacobs

Boxel

Nieveen

1996

Agricultural and Forest Meteorology

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The exchange process in the lower region of a maize canopy is analyzed for two nights. It appears that during calm nights a free convection state develops in the lower region of the canopy. Convective heat is released at the soil's surface and transported directly to the higher portion of the canopy. The released sensible heat at the soil's surface can be easily calculated by applying the Nusselt number for free convection.At night thermal energy is also released through cooling of the canopy. The released heat from the stored canopy heat is of the same order of magnitude as all other energy terms. Conversely during daytime for most agricultural crops this energy term is of minor importance in comparison to the other energy terms.The formation of dew at night is an important process. A maxima1 possible estimate of dew accumulation for a particular night can easily be made by using the potential dew. The potential dew can be deduced more accurately by taking into account the released heat stored in the plant canopy.

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Environmental Instrumentation

Cited by 136 publications

References 0 publications

Profile of the horizontal wind variance near the ground in near neutral flow – K-theory and the transport of the turbulent kinetic energy

Profile of the horizontal wind variance near the ground in near neutral flow – K-theory and the transport of the turbulent kinetic energy

Eddy covariance methane measurements at a Ponderosa pine plantation in California

Nighttime exchange processes near the soil surface of a maize canopy

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