scholarly journals Experimental mass-flux measurements: a comparison of different gauges with estimated theoretical data

1998 ◽  
Vol 26 ◽  
pp. 225-230 ◽  
Author(s):  
D. Font ◽  
M. Mases ◽  
J.M. Vilaplana
Keyword(s):  
Mass Flux ◽  
Field Data ◽  
Theoretical Data ◽  
Trapping Efficiency ◽  
Experimental Plot ◽  
Experimental Site ◽  
Ski Resort ◽  
Flux Data ◽  
Spanish Pyrenees ◽  
Flux Measurements

In experimental snowdrifting mass-flux measurements many different instruments have been tested (Takeuchi, CEMAGREE Mases, etc.). Very often the results obtained are a function of the gauge used. However, in order to compare data from different instruments, orders of magnitude have to be similar.Since 1992, snowdrifting has been studied at an experimental plot at La Molina ski resort (eastern Spanish Pyrenees). The alpine site, characterized by a plateau topography, is located at 2250 m.In this paper, different gauges used to measure snowdrifting mass flux at this site are presented: one snow-collector column and two types of snow traps. Snow-collector columns (prismatic boxes) are permanent installations and are used to measure the mass-flux episode. Snow traps (Takeuchi, 1980: modified) are lighter and more mobile, and they are used for short experiments during a wind episode during which mass-flux data are obtained.The three different gauges are compared and the rate of trapping efficiency is suggested from a comparison of the field data with estimated mass-flux data deduced from empirical formulae (Mellor and Fellers, 1986; Naaim-Bouvet and others, 1996). The mass-flux values obtained at the experimental site are lower than the estimated values.

scholarly journals Experimental mass-flux measurements: a comparison of different gauges with estimated theoretical data

1998 ◽  
Vol 26 ◽  
pp. 225-230 ◽  
Author(s):  
D. Font ◽  
M. Mases ◽  
J.M. Vilaplana
Keyword(s):  
Mass Flux ◽  
Field Data ◽  
Theoretical Data ◽  
Trapping Efficiency ◽  
Experimental Plot ◽  
Experimental Site ◽  
Ski Resort ◽  
Flux Data ◽  
Spanish Pyrenees ◽  
Flux Measurements

In experimental snowdrifting mass-flux measurements many different instruments have been tested (Takeuchi, CEMAGREE Mases, etc.). Very often the results obtained are a function of the gauge used. However, in order to compare data from different instruments, orders of magnitude have to be similar.Since 1992, snowdrifting has been studied at an experimental plot at La Molina ski resort (eastern Spanish Pyrenees). The alpine site, characterized by a plateau topography, is located at 2250 m.In this paper, different gauges used to measure snowdrifting mass flux at this site are presented: one snow-collector column and two types of snow traps. Snow-collector columns (prismatic boxes) are permanent installations and are used to measure the mass-flux episode. Snow traps (Takeuchi, 1980: modified) are lighter and more mobile, and they are used for short experiments during a wind episode during which mass-flux data are obtained.The three different gauges are compared and the rate of trapping efficiency is suggested from a comparison of the field data with estimated mass-flux data deduced from empirical formulae (Mellor and Fellers, 1986; Naaim-Bouvet and others, 1996). The mass-flux values obtained at the experimental site are lower than the estimated values.

scholarly journals Phase Doppler quantification of agricultural spray compared with traditional sampling materials

2017 ◽  
Vol 70 ◽  
pp. 142-151
Author(s):  
R.L. Roten ◽  
S.L. Post ◽  
A. Werner ◽  
M. Safa ◽  
A.J. Hewitt
Keyword(s):  
Fluorescent Dyes ◽  
Droplet Velocity ◽  
Field Phase ◽  
Flux Data ◽  
Sources Of Error ◽  
Close Proximity ◽  
Flux Measurements ◽  
Many Sources

The quantification of spray mass has historically been accomplished by means of fluorescent dyes and various string and ground samplers to capture the dye-laden spray. However, these methods are typically not used in close proximity to orchard sprayers and are prone to many sources of error. The objective of this study was to assess the ability of an in-field phase Doppler (pD) interferometer to quantify spray mass against two common string samplers. Measurements were taken at 0.5 m increments to 4.5 m vertically and 1.0 m increments to 5.0 m downwind from the spray. Converted flux measurements from the strings were compared with those obtained using the pD interferometer. The current pD technology was found to be incapable of collecting equivalent flux data to that obtained from the strings. However, the pD equipment did provide useful data on droplet velocity and size.

Evaluation of tunable diode laser absorption spectroscopy for in‐process water vapor mass flux measurements during freeze drying

2007 ◽  
Vol 96 (7) ◽  
pp. 1776-1793 ◽  
Author(s):  
Henning Gieseler ◽  
William J. Kessler ◽  
Michael Finson ◽  
Steven J. Davis ◽  
Phillip A. Mulhall ◽  
...  
Keyword(s):  
Water Vapor ◽  
Diode Laser ◽  
Absorption Spectroscopy ◽  
Mass Flux ◽  
Freeze Drying ◽  
Tunable Diode Laser ◽  
Laser Absorption ◽  
Flux Measurements ◽  
Diode Laser Absorption ◽  
Vapor Mass

scholarly journals Mass flux measurements at active lava lakes: Implications for magma recycling

1999 ◽  
Vol 104 (B4) ◽  
pp. 7117-7136 ◽  
Author(s):  
Andrew J. L. Harris ◽  
Luke P. Flynn ◽  
David A. Rothery ◽  
Clive Oppenheimer ◽  
Sarah B. Sherman
Keyword(s):  
Mass Flux ◽  
Flux Measurements ◽  
Lava Lakes

Understanding LOTEM data from mountainous terrain

Geophysics ◽  
2000 ◽  
Vol 65 (4) ◽  
pp. 1113-1123 ◽  
Author(s):  
Andreas Hördt ◽  
Martin Müller
Keyword(s):  
Field Data ◽  
Electromagnetic Coupling ◽  
Theoretical Data ◽  
Correction Method ◽  
Topographic Effects ◽  
Mountainous Terrain ◽  
Large Loop ◽  
Transient Electromagnetic ◽  
Conductivity Structure ◽  
Long Offset

Long‐offset transient electromagnetic (LOTEM) data from the Vesuvius volcano, in Italy, show that the EM response of the topography is a potential cause of data distortions. A modeling study was carried out to simulate the effect of mountainous terrain on vertical magnetic‐field time derivatives using a 3-D finite‐difference code. The objectives were to assess the importance of topographic effects and to help identify them in existing field data. The total effect of topography on the LOTEM response can be considered as a combination of four distortions of the corresponding responses for a flat terrain. First, the receiver is at some height above the flat surface. Second, the mountain acts as a conductive body displacing air. Third, large loop receivers are nonhorizontal and sense a combination of horizontal and vertical magnetic fields. Finally, the electromagnetic coupling between the mountain and deeper‐lying structure modifies the structure response. Each of the effects can be identified in field data recorded at Mount Vesuvius. The topographic induced distortions for the model used in this study are moderate in the sense that 1-D inversions of the theoretical data still recover the gross conductivity structure, albeit with small deviations from the true parameters. Although this result might imply that topography might be ignored during the first stage of an interpretation, no simple correction method is evident, so topography will have to be included in any 2-D or 3-D inversion attempt.

scholarly journals Towards standardized processing of eddy covariance flux measurements of carbonyl sulfide

2019 ◽  
Author(s):  
Kukka-Maaria Kohonen ◽  
Pasi Kolari ◽  
Linda M. J. Kooijmans ◽  
Huilin Chen ◽  
Ulli Seibt ◽  
...  
Keyword(s):  
Data Processing ◽  
Eddy Covariance ◽  
Signal To Noise Ratio ◽  
Carbonyl Sulfide ◽  
Lag Time ◽  
Maximum Effect ◽  
Signal To Noise ◽  
Flux Data ◽  
Flux Measurements ◽  
Noise Ratio

Abstract. Carbonyl sulfide (COS) flux measurements with the eddy covariance (EC) technique are growing in popularity with the recent development in using COS to estimate gross photosynthesis at the ecosystem scale. Flux data intercomparison would benefit from standardized protocols for COS flux data processing. In this study, we analyze how various data processing steps affect the final flux and provide a method for gap-filling COS fluxes. Different methods for determining the lag time between COS mixing ratio and the vertical wind velocity (w) resulted in a maximum of 12 % difference in the cumulative COS flux. Due to limited COS measurement precision, small COS fluxes (below approximately 3 pmol m−2 s−1) could not be detected when the lag time was determined from maximizing the covariance between COS and w. We recommend using a combination of COS and carbon dioxide (CO2) lag times in determining the COS flux, depending on the flux magnitude compared to the detection limit of each averaging period. Different high frequency spectral corrections had a maximum effect of 10 % on COS flux calculations and different detrending methods only 1.2 %. Relative total uncertainty was more than five times higher for low COS fluxes (absolute flux lower than 3 pmol m−2 s−1) than for low CO2 fluxes (lower than 1.5 μmol m−2 s−1), indicating a low signal-to-noise ratio of COS fluxes. Due to similarities in ecosystem COS and CO2 exchange, and the low signal-to-noise ratio of COS fluxes that is similar to methane, we recommend a combination of CO2 and methane flux processing protocols for COS EC fluxes.

scholarly journals Gap-filling strategies for annual VOC flux data sets

2014 ◽  
Vol 11 (8) ◽  
pp. 2429-2442 ◽  
Author(s):  
I. Bamberger ◽  
L. Hörtnagl ◽  
M. Walser ◽  
A. Hansel ◽  
G. Wohlfahrt
Keyword(s):  
Linear Interpolation ◽  
Winter Period ◽  
Data Sets ◽  
Gap Filling ◽  
Data Set ◽  
Mountain Meadow ◽  
Flux Data ◽  
Flux Measurements ◽  
Annual Patterns

Abstract. Up to now the limited knowledge about the exchange of volatile organic compounds (VOCs) between the biosphere and the atmosphere is one of the factors which hinders more accurate climate predictions. Complete long-term flux data sets of several VOCs to quantify the annual exchange and validate recent VOC models are basically not available. In combination with long-term VOC flux measurements the application of gap-filling routines is inevitable in order to replace missing data and make an important step towards a better understanding of the VOC ecosystem–atmosphere exchange on longer timescales. We performed VOC flux measurements above a mountain meadow in Austria during two complete growing seasons (from snowmelt in spring to snow reestablishment in late autumn) and used this data set to test the performance of four different gap-filling routines, mean diurnal variation (MDV), mean gliding window (MGW), look-up tables (LUT) and linear interpolation (LIP), in terms of their ability to replace missing flux data in order to obtain reliable VOC sums. According to our findings the MDV routine was outstanding with regard to the minimization of the gap-filling error for both years and all quantified VOCs. The other gap-filling routines, which performed gap-filling on 24 h average values, introduced considerably larger uncertainties. The error which was introduced by the application of the different filling routines increased linearly with the number of data gaps. Although average VOC fluxes measured during the winter period (complete snow coverage) were close to zero, these were highly variable and the filling of the winter period resulted in considerably higher uncertainties compared to the application of gap-filling during the measurement period. The annual patterns of the overall cumulative fluxes for the quantified VOCs showed a completely different behaviour in 2009, which was an exceptional year due to the occurrence of a severe hailstorm, compared to 2011. Methanol was the compound which, at 381.5 mg C m−2 and 449.9 mg C m−2, contributed most to the cumulative VOC carbon emissions in 2009 and 2011, respectively. In contrast to methanol emissions, however, considerable amounts of monoterpenes (−327.3 mg C m−2) were deposited onto the mountain meadow during 2009 caused by a hailstorm. Other quantified VOCs had considerably lower influences on the annual patterns.

Sign in / Sign up

Export Citation Format

Share Document