Modification of the relaxed eddy accumulation technique to maximize measured scalar mixing ratio differences in updrafts and downdrafts

D. R. Bowling, A. C. Delany, A. A. Turnipseed, D. D. Baldocchi, Russell Monson

Research output: Contribution to journalArticle

54 Citations (Scopus)

Abstract

A modification to the relaxed eddy accumulation (REA) flux measurement technique is proposed which maximizes the scalar mixing ratio difference in updrafts and downdrafts. This technique was developed with the goal of measuring the stable isotope (13C/12C and 18O/16O) ratios of updraft and downdraft air and thus the net fluxes of 13C16O2 and 12C18O16O. Current mass spectrometer precision is small relative to measured isotopic gradients in CO2 in the Earth's boundary layer, and the conventional REA approach is likely to be ineffective. The new technique, which we refer to as hyperbolic relaxed eddy accumulation (HREA), uses the conditional sampling concept of hyperbolic hole analysis to control sampling of air during only those turbulent events which contribute most strongly to the flux. Instead of basing updraft/downdraft sampling decisions strictly on vertical wind velocity, CO2 mixing ratio ([CO2]) fluctuations or those of another scalar are also used. Simulations using 10-Hz data show that a wind-based/ scalar-based sampling threshold can achieve a factor of 2.7 increase in scalar updraft/downdraft [CO2] differences over simple REA. During midday periods with strong photosynthetic fluxes, up/down [CO2] differences with HREA of 8-10 ppm are possible, compared with 3-5 ppm for the best conventional REA case. Corresponding isotopic differences can likely be resolved with current mass spectrometers using this approach.

Original languageEnglish (US)
Article number1999JD900013
Pages (from-to)9121-9133
Number of pages13
JournalJournal of Geophysical Research: Space Physics
Volume104
Issue numberD8
StatePublished - Apr 27 1999
Externally publishedYes

Fingerprint

vertical air currents
updraft
mixing ratios
mixing ratio
eddy
vortices
Fluxes
scalars
Sampling
Mass spectrometers
sampling
mass spectrometers
spectrometer
Air
Isotopes
Boundary layers
wind velocity
Earth (planet)
air
flux measurement

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Atmospheric Science
  • Astronomy and Astrophysics
  • Oceanography

Cite this

Modification of the relaxed eddy accumulation technique to maximize measured scalar mixing ratio differences in updrafts and downdrafts. / Bowling, D. R.; Delany, A. C.; Turnipseed, A. A.; Baldocchi, D. D.; Monson, Russell.

In: Journal of Geophysical Research: Space Physics, Vol. 104, No. D8, 1999JD900013, 27.04.1999, p. 9121-9133.

Research output: Contribution to journalArticle

@article{b59397847b4c40b38f17b4d1737571c0,
title = "Modification of the relaxed eddy accumulation technique to maximize measured scalar mixing ratio differences in updrafts and downdrafts",
abstract = "A modification to the relaxed eddy accumulation (REA) flux measurement technique is proposed which maximizes the scalar mixing ratio difference in updrafts and downdrafts. This technique was developed with the goal of measuring the stable isotope (13C/12C and 18O/16O) ratios of updraft and downdraft air and thus the net fluxes of 13C16O2 and 12C18O16O. Current mass spectrometer precision is small relative to measured isotopic gradients in CO2 in the Earth's boundary layer, and the conventional REA approach is likely to be ineffective. The new technique, which we refer to as hyperbolic relaxed eddy accumulation (HREA), uses the conditional sampling concept of hyperbolic hole analysis to control sampling of air during only those turbulent events which contribute most strongly to the flux. Instead of basing updraft/downdraft sampling decisions strictly on vertical wind velocity, CO2 mixing ratio ([CO2]) fluctuations or those of another scalar are also used. Simulations using 10-Hz data show that a wind-based/ scalar-based sampling threshold can achieve a factor of 2.7 increase in scalar updraft/downdraft [CO2] differences over simple REA. During midday periods with strong photosynthetic fluxes, up/down [CO2] differences with HREA of 8-10 ppm are possible, compared with 3-5 ppm for the best conventional REA case. Corresponding isotopic differences can likely be resolved with current mass spectrometers using this approach.",
author = "Bowling, {D. R.} and Delany, {A. C.} and Turnipseed, {A. A.} and Baldocchi, {D. D.} and Russell Monson",
year = "1999",
month = "4",
day = "27",
language = "English (US)",
volume = "104",
pages = "9121--9133",
journal = "Journal of Geophysical Research: Space Physics",
issn = "2169-9380",
publisher = "Wiley-Blackwell",
number = "D8",

}

TY - JOUR

T1 - Modification of the relaxed eddy accumulation technique to maximize measured scalar mixing ratio differences in updrafts and downdrafts

AU - Bowling, D. R.

AU - Delany, A. C.

AU - Turnipseed, A. A.

AU - Baldocchi, D. D.

AU - Monson, Russell

PY - 1999/4/27

Y1 - 1999/4/27

N2 - A modification to the relaxed eddy accumulation (REA) flux measurement technique is proposed which maximizes the scalar mixing ratio difference in updrafts and downdrafts. This technique was developed with the goal of measuring the stable isotope (13C/12C and 18O/16O) ratios of updraft and downdraft air and thus the net fluxes of 13C16O2 and 12C18O16O. Current mass spectrometer precision is small relative to measured isotopic gradients in CO2 in the Earth's boundary layer, and the conventional REA approach is likely to be ineffective. The new technique, which we refer to as hyperbolic relaxed eddy accumulation (HREA), uses the conditional sampling concept of hyperbolic hole analysis to control sampling of air during only those turbulent events which contribute most strongly to the flux. Instead of basing updraft/downdraft sampling decisions strictly on vertical wind velocity, CO2 mixing ratio ([CO2]) fluctuations or those of another scalar are also used. Simulations using 10-Hz data show that a wind-based/ scalar-based sampling threshold can achieve a factor of 2.7 increase in scalar updraft/downdraft [CO2] differences over simple REA. During midday periods with strong photosynthetic fluxes, up/down [CO2] differences with HREA of 8-10 ppm are possible, compared with 3-5 ppm for the best conventional REA case. Corresponding isotopic differences can likely be resolved with current mass spectrometers using this approach.

AB - A modification to the relaxed eddy accumulation (REA) flux measurement technique is proposed which maximizes the scalar mixing ratio difference in updrafts and downdrafts. This technique was developed with the goal of measuring the stable isotope (13C/12C and 18O/16O) ratios of updraft and downdraft air and thus the net fluxes of 13C16O2 and 12C18O16O. Current mass spectrometer precision is small relative to measured isotopic gradients in CO2 in the Earth's boundary layer, and the conventional REA approach is likely to be ineffective. The new technique, which we refer to as hyperbolic relaxed eddy accumulation (HREA), uses the conditional sampling concept of hyperbolic hole analysis to control sampling of air during only those turbulent events which contribute most strongly to the flux. Instead of basing updraft/downdraft sampling decisions strictly on vertical wind velocity, CO2 mixing ratio ([CO2]) fluctuations or those of another scalar are also used. Simulations using 10-Hz data show that a wind-based/ scalar-based sampling threshold can achieve a factor of 2.7 increase in scalar updraft/downdraft [CO2] differences over simple REA. During midday periods with strong photosynthetic fluxes, up/down [CO2] differences with HREA of 8-10 ppm are possible, compared with 3-5 ppm for the best conventional REA case. Corresponding isotopic differences can likely be resolved with current mass spectrometers using this approach.

UR - http://www.scopus.com/inward/record.url?scp=0033608916&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0033608916&partnerID=8YFLogxK

M3 - Article

VL - 104

SP - 9121

EP - 9133

JO - Journal of Geophysical Research: Space Physics

JF - Journal of Geophysical Research: Space Physics

SN - 2169-9380

IS - D8

M1 - 1999JD900013

ER -